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Bio-Intensive Harvest Extension
Vegetable Crops in Cold Climates
By Daniel Halsey
SouthWoods Forest Gardens
#5 in the Homestead Design Series
SouthWoods Forest Gardens 17766 Langford Blvd Prior Lake, MN 5372 612-‐720-‐5001 Southwoodscenter.com
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Bio-Intensive Harvest Extension of Vegetable Crops in Cold Climates
In the temperate climate of the upper Midwest, growing seasons, as traditionally defined,
are short compared to southern regions. This is due to warm temperatures and sunlight gaining
slowly and unpredictably later in spring and diminishing with earlier autumn frosts and cold
night temperatures. As winter snows melt and days grow longer, the last spring frost is still hard
to predict, and late frosts can set back an exposed vegetable garden to replanting or worse,
destroy weeks of transplants. Spring plants in growth are more susceptible to chilling damage,
whereas mature plants acclimate to colder temperatures. 7 Plants having bloomed and then
exposed to a night of freezing temperatures can lose their entire season of fruit. Although autumn
cold temperatures may freeze some plants that will thaw undamaged, each plant species has a
limited tolerance for depth and duration of near or subfreezing conditions.
For the serious food producer, gaining the most calories out of a garden with the least amount of
work involves understanding and utilizing the natural capabilities of plants and proven season
extension techniques. Plants live longer and produce more food, or allow for additional crops.
The right cultivars and thermal capture can buffer the effects of extreme temperatures and
increase the span of time available for planting, growing, and harvesting. In this paper I will
discuss some of the plant cold tolerance and the related species preferred by cold climate
growers, garden design, techniques, planting schedules, and the structures used to extend the
harvest. Publication Update 1/2012 It is January and I am still harvesting carrots and broccoli from the garden. This winter has been unusually mild with 30-50 degree days and little snow cover. This has limited the soil
frost depth early in the season, yet without the snow cover, increases the potential frost depth. Carrots from under plastic and straw are sweet and crisp, a highlight at workshops. Potted broccoli plants in garage windows continue to produce a few florets each week. Now late
January, the weather is turning back to average temps and expected snowfall.
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Many times individual characteristics of a plant or resource are used to develop new techniques,
but the combination and integrated systems using all the available characteristics can increase the
needed effect. Planting cold tolerant cultivars in a heat collecting structure extends the growing
season into otherwise intolerable temperatures.
Understanding harvest extension as a two sided system allows for integration of new plant
cultivars that are cold hardy and finding a system that catches and radiates warmth and enhances
light on sun limited days.
Climate Effects of Vegetable Production
o USDA Zones
Due to climate disruption the fluctuating USDA zones have offered the appearance of opportunity
for extended crop seasons, yet still do not remove the climate extremes in the area. The warming of
fall and spring are deceptive since other ecological factors such as disease and pests will also
flourish in a climate more suited to their life cycles. Also, the day lengths have not changed. Plants
still need light to grow and the warm temperature only marginally effect that need.
It is the extreme weather situations that season extension is buffering. The months that the coldest
temperatures damage or kill annual plants in exposed gardens, growers attempt to select plants
that will withstand lower temperature to the degree that protected growing systems can raise the
shelter’s temperature. Intermittent extremes in low temperature can be managed in short
durations. Some weeks may preclude any exposed plants, even within protective structures unless
heat sources are used. Every few degrees a passive growing system can raise the minimum
temperature over the coldest nights means higher yields, faster growing plants, and more plants to
choose from. Methods to extend the growing season have been devised in all latitudes over
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centuries. Across the world, latitude effects the light availability as the season change and sun dips
lower in the sky. Maritime regions, lake effects such as in northern Michigan, and the Pacific loaded
Jet Stream across the northwest United States buffer the extreme temperatures otherwise
experienced in the mid continent states. Literature citing growing regimes from the certain latitude
cannot be generally applied across the same latitude. Local weather conditions, knowledge, and
history must drive the invention of new systems. USDA zones for Minnesota are below. The
extreme zone minimum temperatures can be sustained or intermittent for weeks. Most of the
coldest days coincide with the post solstice winter days of late January to February. A time when
harvest extended plants have been exhausted and small transplants are being started inside.
Zone Fahrenheit Celsius Example Cities 1 Below -50 F Below -45.6 C Fairbanks, Alaska; Resolute, Northwest Territories (Canada)
2a -50 to -45 F -42.8 to -45.5 C Prudhoe Bay, Alaska; Flin Flon, Manitoba (Canada) 2b -45 to -40 F -40.0 to -42.7 C Unalakleet, Alaska; Pinecreek, Minnesota 3a -40 to -35 F -37.3 to -39.9 C International Falls, Minnesota; St. Michael, Alaska 3b -35 to -30 F -34.5 to -37.2 C Tomahawk, Wisconsin; Sidney, Montana 4a -30 to -25 F -31.7 to -34.4 C Minneapolis/St.Paul, Minnesota; Lewistown, Montana 4b -25 to -20 F -28.9 to -31.6 C Northwood, Iowa; Nebraska 5a -20 to -15 F -26.2 to -28.8 C Des Moines, Iowa; Illinois 5b -15 to -10 F -23.4 to -26.1 C Columbia, Missouri; Mansfield, Pennsylvania 6a -10 to -5 F -20.6 to -23.3 C St. Louis, Missouri; Lebanon, Pennsylvania 6b -5 to 0 F -17.8 to -20.5 C McMinnville, Tennessee; Branson, Missouri 7a 0 to 5 F -15.0 to -17.7 C Oklahoma City, Oklahoma; South Boston, Virginia 7b 5 to 10 F -12.3 to -14.9 C Little Rock, Arkansas; Griffin, Georgia 8a 10 to 15 F -9.5 to -12.2 C Tifton, Georgia; Dallas, Texas 8b 15 to 20 F -6.7 to -9.4 C Austin, Texas; Gainesville, Florida 9a 20 to 25 F -3.9 to -6.6 C Houston, Texas; St. Augustine, Florida 9b 25 to 30 F -1.2 to -3.8 C Brownsville, Texas; Fort Pierce, Florida
10a 30 to 35 F 1.6 to -1.1 C Naples, Florida; Victorville, California 10b 35 to 40 F 4.4 to 1.7 C Miami, Florida; Coral Gables, Florida 11 above 40 F above 4.5 C Honolulu, Hawaii; Mazatlan, Mexico
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Temperature Ranges
Minnesota Climate Average annual precipitation - Northwest: 19 inches/year Southeast: 34 inches/year
Average annual snowfall - Northeast: 70 inches/year Southwest: 35 inches/year
Latest spring freeze -‐ April 29 -‐ metro area May 27 -‐ far north
Earliest fall freeze -‐ October 5 -‐ metro area September 16 -‐ far north
Average temperature Spring -‐ 36 F north 44 F south
Summer -‐ 60 F north 70 F south
Fall -‐ 38 F north 46 F south
Winter -‐ 6 F north 16 F south
Daylight Hours
As stated previously, daylight hour gradually shorten then lengthen in winter months. The speed
at which the changes occur is slowest at the winter solstice after which the daylight begins to
increase and accelerate in change. The length of day is only one part of the issue. The quality of
light also is diminished. As seen in the chart below, in Minneapolis the intensity of the light on
December 22 is almost 1/3 (39%) the intensity of June 22. The days are in a plant sense, very
dark.
Latitude of Minneapolis, MN: 45o N
Zenith Noon sun Radiation
Date Declination angle angle intensity (%)
March 21 0 45 45 70.71
June 22 23.5N 21.5 68.5 ~92.4
September 23 0 45 45 70.71
December 22 23.5S 68.5 21.5 ~36.65
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This brings up another issue for northern growers. Not only do they have to increase the length of available light, they must increase its intensity 235% to achieve summer efficiency (June 22). Duration and quality of light reflect
directly in the growth of plants. Temperature duration and quality also play a large role in plant development.
http://www.gaisma.com/en/
Clock Time
May 16th Months
Darkness Sunrise
Sunset
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Growing Degree Days
Ambient temperature regulates plant functions, biological and chemical activities, thus the heat a
plant is exposed to over time promotes its growth. This influence of temperature has more of an
effect than light, moisture, or nutrition since all the processes involved are temperature
dependent. Growing degree days (GDD) is the measurement which plant drives growth. All
other resources met the GDD is the catalyst for growth and can be monitored by growers.
Calculating and using degree days takes only some simple math and a base temperature, the
minimum temperature for plant development, for the plant monitored. Combining the minimum
(Min T) and maximum (Max T) air temperature of a day and dividing by two will give an
average daily temperature. The difference between this number and the base temperature of a
specific plant will give a sum. If positive, that equal the degree days for that day. The insect pest
world has been studied well for calculating their degree days for spring arrival and seasonal life
cycles. Many commercial crops have been plotted for their development over degree-days. Rape
seed / Canola has been mapped out by the Canola Council of Canada using a 0ºC or 32ºF base
temperature. Stages of growth by degree days are enumerated from the emergence of cotyledons
and subsequent leaves in stage one, to stage six when flowering begins. Stage seven is seed
development. Stage eight, seed maturity to harvest. Each stage is divided in tenths for more
exacting stages of development. Canola needs 1249 - 1382 Celsius degree days to mature
(CGM).
• Lengthened seasonal daylight hours can reduce the GDD required for plants. In Albert,
Canada the GDD for Canola is reduced 150 GDD
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Soil temperature effects germination and crop development. In spring soil temperature is relative
to soil depth. Warm surface soils may be as much as 15 degrees cooler an inch or two below.
Low temperature and moisture reduce the seeds uptake of moisture needed to germinate. Degree
days also effect the seed more than minimum soil temperature for emergence. With variations in
immediate soil, seeds can take 75 to 150 Celsius degree days to emerge (CGM). Cold tolerant
vegetables may be planted earlier and may have a lower degree day Base temperature.
Garden vegetables vary in cold tolerance and emergence temperatures. The early spring plants or
over-wintering plants generally grow better in moderate to cool temperatures. Their seed also can
germinate in colder soils. Spinach being planted in late fall can overwinter and reemerge in the
spring. The fast growing seedlings are more susceptible to frost damage. With Canola, the
cotyledons are more fragile to freezing while the three to four leaf stage can withstand a few
degrees lower temperature. Winter readiness with tolerances between -15º and -20ºC is at the six
to eight leaf stage. It would be good to compare leaf stages as a guide for winter readiness. i.
After a hard freeze, it may take four to ten days for the plant to renew growth. The growing
point, at the center of the leaf rosette, must be undamaged.
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Base Temperatures for selected vegetables General plant growth requires a base temperature of 41ºF Corn and Beans 50ºF Pumpkins and Tomatoes 56ºF Lettuce 40ºF Peas an Asparagus 42ºF Potato 45ºF
SOURCE: Agrometeorological Centre of Excellence
(http://www.gov.mb.ca/agriculture/climate)
Season Extension
Plastics are heavily used to extend seasons, collect heat for soil, and deter weeds and insects. Research into new materials, translucent color effects on plants, and environmental residues continues.
Low Input Heat and Cold Mitigation Techniques
Plastic Mulch 8
o Plastic Mulch is used for early season soil heating. It is laid tightly on the soil two to three weeks before planting with edges buried into the side of the row.
Types o Black
Warms soil 2ºC - 4ºC at 2" depth. Prevents weed seed germination. Needs direct contact with soil for efficient heat transfer.
Photo-degradable • Same as above with decomposition from light
exposure, said to be left in the field after harvest (I have heard its field residue is problematic to mechanical planters, buried edges do not degrade).
Biodegradable • Same as straight black. Starch based, decomposed
by soil organisms. Recommend it be field-tested. o Clear
Warms soil 4ºC - 8ºC at 2" depth. May be used with direct seeded crops. Weeds may
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Germination under plastic and requires pre-plant weed control.
o White
Cools soil -1ºC, Cools soil for cool season crops. Requires pre-plant weed management.
Infrared Transmitting
• Warms soil 6ºC with selectively pervious to certain light wavelengths while deterring weed seed germination. More expensive and may reduce tomato and pepper yields compared to black plastic.
Row Covers
Row covers are used to mitigate temperature extremes and protect plants from insect damage. Use
of row covers has shown to accelerate production and increase yields (4., Wells and Loy, 1985).
They are used to increase air and soil temperature under the canopy and protect young seedlings
from wind damage. 8 The long sheets of material are perforated to varying degrees and allow for
moisture and air exchange while slowing the loss or gain of temperature under the cover near the
plant. Soil is also protected and buffered from ambient changes in air temperature. Air temperature
gains under the fabrics range from 1-‐5º C in early Spring under perforated PE plastic to 5.9 -‐ 6.8ºC
in summer (Wells and Loy 1985). Soil temperature were
4-‐5ºC higher (Motsenboker and Bronnano 1989). Greater
increases also are delivered by using black plastic
"mulch" ground covers. In the Labik and Siwek trials,
Lettuce increased yields by 110.9% and Watermelon
increased 263.6%. All trials were in comparison to open
ground plantings.
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Depending on the cultivar, row covers can be used to cool the soil temperature for lettuce
production, however the use of plastic mulch increases the soil temperature negating and shading
effect. In the Libik and Siwek trials, the first crop of lettuce came from fabric row covers. Row
covers can be used as temporary protection for young plants and removed as they harden to the
open environment. This is often done with smaller transplants or direct seed plants. The cover must
be removed when temperatures under canopy reach the 35ºC -‐ 35ºC range since plants may be
damaged or killed. High temperature can also cause fruit deformities and inhibit pollen. Row covers
must also be removed for bee pollination, such as with vine crops. 8 .
Supported Row Covers
Low Tunnels
There are mainly two kinds of materials for row cover, perforated plastic sheeting and
polypropylene woven fabric. Each has its benefits and failings. The plastic sheeting retains
the most heat after sunset yet is slower to warm in morning. The woven fabric retains less
warmth in nightfall, but exchanges for warmth in the morning more quickly. When each is
used with plastic mulch, the effects are magnified. On sunny days the combined two plastics
layers will increase the air and soil temp beyond tolerable limits of some plants. Woven row
covers either floating or on hoops exchange air faster and allow for solar heat to escape.
Floating Row Covers
Floating row covers, exclusively woven fabric, use no
structure to rise above the plants. The light material
rests on the plants directly. They are not used for tall
stem plants such as peppers. The sides are held down
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by mounded soil and although some abrasion to soft plant surfaces can occur from wind
movement, this is the least expensive summer material for the most effect. The limits of this
lighter fabric may come in colder seasons when temperatures drop to a low average. The season
and type of vegetable grown may determine the type of cover material used.
Radish Trial
In 1986 Loren and Young 9. did trials with various commercial row cover materials. Reemay was
used for radishes and winter squash. Among other benefits the spun fabric row covers
accelerated plant production. Covered plants had 3.5 times the edible bulbs than uncovered.
Plants were harvested in 21 days as apposed to the 27 day expectation. Abrasion on leaves was
observed in the Reemay covered plants.
The woven fabric Reemay increased the daily maximum and minimum temperature and heat
units (GDD) per day. The heat units were 1.5 to 2.4 times the GDD of the uncovered areas using
a 50ºF base temperature. In cucumber plant trials, plants with Reemay and black plastic mulch
yielded an average of 49 cucumbers as compared to the covered plants with no mulch baring 22,
and bare field plants that yielded an average of 17 9.
Degree day results for the period from May 16th to June 5th increased considerably under the
floating row cover Reemay. Whereas the uncovered areas had 157 GDD the covered areas had
458 growing degree days during the same period, When the trials started on May 16th the
covered row measurement was already a daily 17 GDD. It was not a comparison point for the
study, but the areas with floating row covers could have probably started the trail a week earlier
than the control. This would have been a classic opportunity for season extension beginning the
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growing season days or weeks earlier. In the case of the radishes, this would possibly have
brought them to market another week early (two weeks total).
Also know as low tunnels, these vary in size from mature plant height to a
height allowing growers to access the crop without removing the canopy. The
plastic is vented through small perforations. Research in Ontario Canada has
shown earlier harvests of Cucumber, lettuce, peppers, and melons. Row covers
must be removed before flower set on some crops. 11.
Individual Plant Techniques
Cloches are any covering that is for a specific plant.
Bell Jars The bell jars and glass covers were
propped up during the day and dropped
at night to keep the warmth. As early as
1659 English gardeners were using them
to protect fragile plants. The jars were
not vented and needed daily
adjustments, but increased the air
temperature considerably in the damp
British Isles. The thermal mass of the glass held heat for some time.
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Juice Jug
The simple
plastic jug is
often used to
protect plants
from frost. This technique used the soil heat and air o retain daylight warmth. The top is removed
during the day.
Water Walls add a large amount of thermal mass to the plant
proximity. The water will radiate heat as it cools for a considerable time.
Any container can hold the water will do as long as it encloses the plant.
The density of the thermal mass insulates from temperature changes and
stores heat to radiate.
Dense Surrounds The dark and dense rubber of
tires collect and hold warmth for slow release
during frosty nights. Covered tires increase the
effect. 11. They can bee added to garden as needed
late in the season. Drainage holes should be made
to keep water from collecting in the tire.
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Hoop Houses
Like the floating woven row covers, hoop houses are the least expensive green house effect available and many are home built with conduit, plastic tubing, and even livestock fencing. Hoop houses house raised beds or container gardens. Unlike high tunnels that are directly planted in the enclosed ground soil, hoop
houses are shelters for many varies uses.
Hoop houses are shorter than high tunnels and crops cycle through the seasons for starting transplants, growing high value container crops under the canopy or for later outside planting. Used by low volume growing or residential gardeners, access is limited by a door on either end and the floor may be wood chips, planks, or gravel. The underlying soil has minimal use for thermal mass although it does have some late season radiant heat. Water barrels for heat storage and compost piles give off some heat if managed well. Many growers start with hoop houses and move to or add high tunnels with the experience.
Cupolas
In 1994 M. Cerne 5 trialled cupolas along tunnels, hit beds, and open air plantings. The structures had a 7'9" x 4'9.5" foot print , but no images are found of the Cupolas described. It is likely that the structures were peaked mini-greenhouses mostly likely vented from the top. The results did not differ much from plastic tunnels.
High Tunnels Spinach Trial
In 2005, Sharon Knewton and Ted Carey of Kansas State University trialed 26 spinach cultivars in a 3 season Haygrove high tunnel and in adjacent field plots. Poor germination caused a second seeding 3 weeks later due to temperature effects. The second planting took place on September 27th. Germination was still between 15 & 11 percent. With such low rates of germination, and using a wheel planter, the seeds were dispersed with insufficient density to deter later weeds. Hand broadcasting was seriously considered. Leaf texture and growth habit
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varied between cultivars. Increased density of seeding again would encourage a more upright growth habit. Two or the varieties were completely prostrate. The first harvest was in November. Yields ranged from .08 to 2.2 pounds per 10 square feet. The plants were then left to over-‐winter in the tunnel. March harvest yields varied between 5.12 and 7.58 pounds per 10 square feet. The spring plants had more leaves per plant than in the fall. In May some of the the plants were observed to have gone to seed, had elongated internode, or were bolting. Eight cultivars including Interceptor, Space, Umbria and Blackhawk, had the best appearance and least bolting. Of the final best looking plants, all were among the least productive. The trial was inconclusive and continued.
The high tunnel has become the serious choice for season extension. The universities of Minnesota, Michigan and other states are researching and promoting the use of high tunnels in commercial agriculture. Best practices are shared at regional conferences and numerous publications. Many colleges have manuals specifically for the climate and weather of the regions involved. With this expansion of use has come the attention to biological effects of the tunnels on soil and plant health. Long term use of tunnels without soil remediation has caused issues of salt build up, over-‐wintering pests, and disease. The accelerated vegetable production depletes the soil of nutrients having produced as much as six times the yield of a comparable outdoor field (Michael Patrick, Moses Conference 2011). High tunnels can be over 100' long and 36' wide. A popular option is to have shortened structures that can move up and down the field on rails or by skids.
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A table from the Doug Waterer's report in Hort Technology shows the dramatic accumulation of
Growing Degree Days over open field or low tunnels12. As stated in the findings, although the
tunnels collected the heat well and was managed by venting, managing the temperature in the high
tunnels for differing crops was problematic. Tomatoes benefitted from delayed ventilation until the
temperature reached 104ºF. Peppers however suffered under those conditions. Frost protection in
high tunnels was comparable to low tunnels (No data shown). Waterer did not combine high and
low methods in this study.
Waterers found that although Muskmelon did well in the high tunnel and set and brought fruit to
maturity, the plants were under stress from the heavy yield. In 1998 the warm temperatures made
for little difference between regimes for marketable yields, however, in the cooler 2000 season the
high tunnel plants preceded the first frost with harvestable fruits. Overall high tunnels had 59%
higher yields. Sugar content and flavor was unaffected. In conclusion, Wateres states that high
tunnels accelerate growth, improve yields of standard warm vegetable crops, were most beneficial
during cooler growing seasons, and delivered good quality crops with less insect and disease
problems.
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The moveable high tunnel allows small growers to sell a diverse number of plants that have
differing tolerances and optimum conditions for growth. By moving the tunnel the grower
can warm soils in spring for
early cold hardy crops and
move the tunnel away once
temps have raised to plant
tolerable levels. Then a second
crop that is less cold tolerant
benefits from the canopy. The
tunnel plan can have four or
five positions during the
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seasons. The growing season can start in February with carrots, move to soil warming and
tomatoes and then fall spinach through November and winter leeks which are already
under row covers at the field end since May. Rotating through the field plots allows some to
be fallow during the season an others to grow multiple crop relays.
The Ontario Ministry of Agriculture, Food, and Rural Affairs recommends removing the
plastic off the high tunnel off season (winter). This extends the life of the plastic, prevents
structural damage from snow, and allows increased soil moisture beyond drip irrigation
lines. The plastic is usually rolled and tied to the ground on one side, covered, and on a
warm late winter day replaced on the frame for spring soil preparation.
Combining the benefits of all the above structures within a high tunnel has improved the
heat collection and season extension for cold climate growing. The key to much of the
progress is viewing the tunnel environment as a dynamic environment able to buffer
seasonal changes. The tunnel can be used for harvest extension like growing late season
vegetables for early to mid winter harvesting. The tunnel delays the soil freeze for weeks
while tubers and roots lay in the soil for later than typical harvest. Their best storage being
in the ground until needed. My personal stand of Sunchokes () was harvested in the fall of
last year, this spring while preparing the soil for planting I found missed tubers that were
twice the size of the harvest months before. The deep snow and straw protected them as
they continued to thrive 6" to 10" beneath the surface. A hoop house or row cover above
the tubers would allow later harvesting and longer growing periods for the perennial
vegetable.
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My only concern with the structures is the amount of plastic used and required each year.
Plastic mulches are soiled and wet, unsuited for recycling. Large hoop house and high
tunnels need the canopy replaced every few years. Irrigation lines and drip tapes degrade
over time and lose usefulness. All which makes for large piles or bales of landfill ready
plastic. I hope to find ecological solutions to replace these plastic materials.
Other than materials which can be adapted as available, the tunnels seem to be the
cheapest and best solution to season and harvest extension. The next level of season
extension and micro-‐climate options is the green house. Many times more expensive, the
immobile green house allows for permanent systems and creative installations. Prior to
plastics, this was the only option for centuries, for those with the means.
Cold Climate Harvest Extension
In the scheme of season extension the two limiting factors being considered are heat and
light. These are then the design drivers for all inventions, to mitigate the cold and enhance
the plant available light.
Mature Plant Protection in Fall
Foliar Sprays
• Frost Shield -- by Maz-Zee S.A. International, P.O. Box 82717, San Diego, CA 92138. Available from Peaceful Valley Farm Supply.
• Frost Away -- by Bonide. Available from Mellingers.
• Wilt-Pruf -- by Wilt-Pruf Produces, P.O. Box 469, Essex, CT 06426.
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• Frostguard -- by Custom Chemicides, P.O. Box 11216, Fresno, CA 93772. Available from local farm suppliers
Lowers freeze temp of foliar water ten degrees, strengthens cells walls, and penetrates leaf membranes. 4-6 weeks active.
Creating Persistent Micro-climates
Cold Frames are small “green house “ type structures at ground level where growers start spring
plantings and harden transplants. The soil is warmed and some thermal gain is achieved. They
must be monitored closely for excessive heat build up.
Outside Temp 0F o Temperature Differential o Night < 20F warmer o Day 10-‐15 F warmer o Zone 5 Avg, 10-‐15 F o SpringTarget 70F o Fall Target 60-‐65F
Proximity to Structures
Radiant heat emanates from solid structures as they cool. As is the case with water walls, barrels,
and stone. The buffering effect slows the cooling of the near plants as the aggregate temperature is
more stable. (Markhart, A, 2011) Partitions, stones, and structures within a garden can store
daytime heat and radiate during night. Slowing the vertical heat loss also mitigates the decreasing
ambient temperature. Covers over plants contain the soil radiant heat and deflect cold air moving
across the garden. Air is also a source of heat storage. Large tunnels hold more heat than small and
slow the temperature change in cold weather. Adding additional layers like row tunnels or floating
covers with a tunnel magnify the effect. Partitioning the air also slows the heat loss and deters
convection, much like insulation.
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Mid Latitude Aspect Higher Latitude Aspect
Aspect
Progressive Techniques
Thermal Mass is the density in a material that allows
it to store heat or cold. The density is slow to change temperature,
and radiates that difference to the surrounds as ambient temperature changes. It buffers
the change in the area of extremes. Air, water, stone, sand, and soil equalized to the
ambient temperature at different rates. Anything that has a thermal mass less than air is
considered insulation, because it inhibits temperature exchange. Insulating fibers, straw or
layered glass will inhibit temperature changes, but not store heat or cold. 14 Also called the
Thermal Flywheel, thermal mass is the rate at which a material equalizes with the ambient
temperature gaining or losing heat. In one respect, glass can b used to capture radiant heat,
and thermal mass can store it. This is done in green houses and growing spaces with
barrels of water, stone, and even soil. Site Selection using the south face of a masonry
building can provide 5-‐6 degrees of frost protection. 11.
Aspect
South facing slopes collect more sunlight heat and drain away cold air to lower areas. Tender
plants can be extended up to two weeks in fall and spring. 11.
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Earthen Walls and Subsoil Solar Heat Storage
Earth Ships use the thermal mass of the ground to assist in
heating and cooling. The southern aspect collects heat in
winter.
Below Grade growing spaces are protected from heat and
at the same time have good light since the sun is many
time directly overhead in these latitudes. In Bolivia,
Walipinis were used just this way to cool the air. Dug into
the hard soils, the walls created thermal mass heat temperature buffering. At the right
aspect the sun would shine a great part of the day.
Bolivian Walipini
Victorian Pit Gardens did much the
same as Walapini, though much smaller
and for ornamental plants more than
food production. The thermal mass,
glass and aspect to the sun warmed the
air inside. Walipinis mitigated the harsh
heat conditions with cool deep soils,
while the Victorian pit gardens collected
warmth.
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Greenhouse
Above grade raised beds warm sooner in spring 8. Making soil workable. Drainage is better
attended also with good soils.
Above ground or below ground, structures design to mitigate hot or cold temperatures still have
the issue of light management. Any semi-‐permanent structure needs to be able to catch the sun at
all times of the year.
Light Reflection:
As stated previously, length of exposure to sunlight in winter has only 39% the intensity of summer
sun. The short days are also darker. Reflecting light into growing spaces add some heat, but add
more valuable light. Doubling or tripling the intensity is difficult. Without artificial light few options
are available. One option is to use shade tolerant cultivars to reduce the light requirements. Some
plants can tolerate shade, but may not thrive or fruit. More light means less energy used for stem
elongation. The combination of frost tolerance and shade tolerance makes a plants a good candidate
for protected winter production..
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Partial Shade Tolerant Amaranth (Grain) Amaranthus Arugula Eruca vesicaria Beet Beta vulgaris craca Tolerant to 15ºF Tuberous Begonia Begonia tuberhybrida Broccoli Brassica oleracea italica Cabbage Brassica oleracea capitata Caraway Carum carvi Cauliflower Brassica oleracea botrytis Chard Beta vulgaris cicla Coriander (Cilantro) Coriandrum sativum Scented Geranium Pelargonium graveolens Jewelweed Impatiens capensis Kale Brassica oleracea acephala Kohlrabi Brassica oleracea caulorapa Lambs Quarters Chenopodium album Lentil Lens culinaris Lettuce Lactuca Dano Lettuce Lactuca 'Dano' Integrata Red Lettuce Lactuca 'Integrata Red' Miner's Lettuce Claytonia perfoliata Love Lies Bleeding Amaranthus caudatus Love-in-a-Mist Nigella damascena Marigold Calendula officinalis French Marigold Tagetes patula Marjoram Origanum majorana Mustard Brassica alba Mustard Green Brassica juncea Nasturtium Tropaeolum majus. Onion Allium cepa Oregano Origanum vulgare Pansy Viola tricolor Parsley Petroselinum crispum Pumpkin Cucurbita maxima Rutabaga Brassica napus napobrassica Summer Savory Satureja hortensis Spinach Spinacia Cold Tolerant to 8ºF Summer Squash Cucurbita pepo Sweet Alyssum Alyssum saxatilis
Shade Tolerant Tuberous Begonia Begonia tuberhybrida Jewelweed Impatiens capensis Miner's Lettuce Claytonia perfoliata Cold tolerant to 11ºF
Oregano Origanum vulgare
Potato Solanum tuberosum
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Lemon Verbena Aloysia triphylla Violet Viola odorata Watercress Nasturtium officinale
Reflected light can come from structures and fences, buildings with south facing glass or white walls.
Buildings with reflective paint (white) . Fabrics and simple sheets hanging on the away side can
reflect sunlight into the plants. Plastic sheeting, some with metallic surfaces can direct sun back to
the garden area, and soft sky light on cloudy days.. Snow in winter the snow can be piled up around
a green house or tunnel reflecting sun and increasing the available light for plants. Trees covered
with snow also reflect light, Coniferous trees hold snow longer tan deciduous. Poplar and white
barked trees can reflect some light.
Growers in cold climates use compost heat from static piles within a growing space. Growing
Power of Milwaukee, Wisconsin uses the combination of compost, large fish tanks used for
Aquaponics, and the passive solar of green house windows to raise the air temperature.
Ground source geothermal heat pumps are 400% efficient in extracting heat from circulating
underground water loops. A comparatively high capital investment for a large space, but much
cheaper than others to use over time.
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Soil Temperature Network
Soil temperature is the signal for many growers to be in the fields with seed. Select farms across the states have soil probes monitoring the fluctuating soil temperature. Germination of the seeds depends on soil moisture and temperature. The chart below is a farm in Eden Prairie, Minnesota.
http://gis.mda.state.mn.us/maps/csgsoil.htm
Germination Temperatures
Garden plant list - Appendix A
Spring and Fall Cold Soil Species - Appendix B
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Early Spring and Fall Plantings
According to Carol Ford in her Northland;'s Green House Manual, Winter is divided up into
three times, Diminishing Light, Solstice, and Expansion of Light. For each there are plant
cultivars that either tolerate the diminished light or don't care. She likes the "don't care" plants.
She suggests Arugula and Mustards as the days grow shorter. Arugula grows fast but mild in the
cool days.
o Diminishing Season -Late September to Mid-November crops
Leaf Lettuces Claytonia Vitamin Green Red Russin Kale Bull's Blood Beets Chard Mizuna Asian Green (Nov)
o Solstice Season- Late November to Early January
Chinese Cabbage Pac Choi Mustard Greens Garden Cress Tatsoi Tokyo Bekana
o Expansion Season
Mixed Lettuces
o Perennial Species
It is important to look at cultural sources of cold climate growing techniques. Areas with short
seasons and high altitude. Growers in upper latitudes in Canada, Europe, Asia and South America
may have information and techniques useful for other cold climate growers. The University of
Idaho's Short Season, High Altitude Series gives good information on practices for those areas. It
29
deals with elevations above 4500 feet or USDA hardiness zone at 4 or less, or 110 days of frost free
growing days. Bulletins 859 covers season extension, winter plant protection of perennials and
small shrubs. Bulletin 863 lists vegetable adapted to the climate. The immediate lesson in Idaho is
selecting the right plants. Much like John Berehbaum of Michigan State who promotes, "The right
plants in the right place, at the right time". Many of the vegetables are harvestable in 60 to 100
days.
Pre-Season Transplants
Transplant Limitations
Suitability
Problem Issues
o Transplant Shock o Plant suitability o Increased labor o Sterilization of planting
media o Capital intense
investments o Environmental controls in
heat, light, pests, disease, and sanitation
Well Transplanted
o Tomato o Lettuce o Cabbage o Brussels Sprouts o Broccoli
Transplant Tolerant o Celery o Onion o Pepper o Eggplant
o Cauliflower
Transplant Sensitive o Cucurbits o Corn o Legumes
Transplant Damaged o Tap Roots
Beets Carrots Turnips
Benefits from transplant use.
o No environmental stress during early growth stages
o Protection from disease pathogens and insect damage
o Controlled growth for uniform shape, timing and quality.
o Reduced loss from non-germination o Efficient use of water and fertilizers o Efficient use of space o No thinning
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Root Injury and Shock
Injury Prevention Wide Spacing, Deep Planting Mix Individual Plant sections Soil covering roots at transplant Seedlings at optimal range for transplanting
• Seedlings still in a vegetative growth state transfer better than plants in the reproductive stage.
• Younger seedlings better accept transfer, but are susceptible to injury.
No root or shoot pruning Brushing daily the tops of young plants, 2.25 inches high, reduced the
plant growth by 50%. This reduced stem elongation and damage during transplanting.
From Using Transplants in Vegetable Production Pub# 8013, Schader, Wayne L., UCLA, 10. Division of Agriculture and Natural Resources
Seasonal Crop Rotations, Successions, and Relays
Rotation Principles
Seasonally or annually repeating a vegetable in the same garden space reduces yields over time and increases the disease and insect pressure. 1 Crop rotation contributes to disease suppression, less compaction, increased microbial communities, and improved soil structure. 2
Factors reducing potential
• Soil borne diseases • Species specific nematodes • Soil related insects • Lower Organic Matter or Limited Diversity, of nutrients and organic
material • Build up of toxic chemical Residues • Exhaustion of species specific minerals
Important Interacting Vegetable Families
• Pea, Legumes • Goosefoot • Mustard
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• Parsley • Nightshade • Gourd • Composite • Lily • Grass • Mallow
Using vegetable family groups is an easy way to keep a rotation simple and reduce competition for nutrients, insect pressure, and allelopathic effects. Some families can be intercropped and rotated in fewer groups. 1
Some vegetable groups should not follow others.
Common vegetable diseases can sustain themselves on various species and persist in the soil for years. For this reason rotations are designed to retard the spread of disease.
Examples of disease persistence in soils
o Fusarium Root Rot, 2-3 year
o Cabbage Club Root, Mustard Family Fungal Disease, 4-5 years
o Tomato Canker, 3 years
o Corn is an alternate host for Pink Root Rot. Onions following corn can be severely effected
o Tomato Verticillium Wilt Fungus, Nightshade Family, Indeterminate persistence in soil
Resistant Cultivars: Carnival, Celebrity, Santiago
o Root Rot Nematode effect Tomatoes, Carrots, and Potatoes. These vegetables increase the nematode population. 1
Alliums, watermelon and certain black eyed peas are Nematode resistant
Grasses, such as corn suppress root rot nematodes.
Sudan Grass Hybrid, "Trudan 8" is a biofumigant for the reduction of nematodes when used as a cover crop 6.
Elbon and Winter Rye inhibits Nematodes
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Organic allelopathic toxins
Corn toxins in decomposed stubble can inhibit the next crops.
Inhibits root growth of Lettuce, Beets, and Onion.
Nutrient deficiency
Tomatoes and high nutrient species can deplete the soil for the next crop. Soil testing will report deficiencies while soil amendment and cover crops rebuild nutrients
Fresh garden plots from previous turfed areas are susceptible to existing turf grubs and active insects. Root and tuber crops may especially be affected. It is preferable to plant Corn, Watermelon, and Squash the first year of a new garden bed using existing turf soil.
Groups in rotation.
Single Season Rotation Example
By order of garden space in a quad garden.
o Season 1 GRASS PEAS NIGHTSHADE MUSTARD
o Season 2 PEAS NIGHTSHADE MUSTARD GRASS
o Season 3 NIGHTSHADE MUSTARD GRASS PEAS
o Season 4 MUSTARD GRASS PEAS NIGHTSHADE
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Coleman's Maine Back-up Winter Crops o Oct., Nov., Dec. o Arugula. Mache
• January o Arugula, Carrot, Spinach
• February o Arugula, Carrot, Spinach, Mizuna, Claytonia, Lettuce, Chicory, Radish
• March o Arugula, Carrot, Spinach, Mizuna, Claytonia, Lettuce, Radish, Minutina
Relay Intercropping (Coolman and Hoyt 1993) combines the best of short duration crop rotation while planting species in a mixed regime. Plants are started in staggered stages and removed as other plants are transplanted in. Usually seeds start first in early season, then a series of other crops are transplanted in as space and temperature allows.
LER
Land Equivalent Ratio
In 1980 Mead and Wiley developed the LER index for measuring yields in intercropped fields. Yields are calculated as intercrop yield over mono-‐crop yield.
Each plant is measured on a field as a mono-‐crop and then by calculated by relative space used for intercropping. In Brian Kahn's Intercropping froField Production of Peppers, he reviews the studies he collected and compares the different plant families and their interaction in various combinations.
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Intercropping Peppers and…
the Allieceae (Onion) Family
Peppers increased 59% when intercropped with onions and although the onions yield fell 36%, only 30% of the space could be used for onions when the plant spacing was completed (Prabhakar and Shukla 1990).
Kubra, et al (2008) focused on the spacing of peppers and onions. The goal was for an LER of greater than 1. 1 is equal to the monocrop yield of the same area. Spacing Peppers as the primary crop at 60 x 30 cm and onions at 15 x 40 cm gave an LER of 1.18. Placing onions as the primary crop at 15 x 20 cm with peppers at 60 x 45 cm reduced shading and returned an LER of 1.16.
Brassicaceae (Mustard)
The most striking is the results from a Kaur and Khurana 2008. Intercropping in cabbage was tomato, muskmelon, peppers, and cucumber. The LER of the cabbage and tomato crop was 5.4 LER. The cabbage pepper intercrop was 3.7 LER.
Ina New Mexico study by Guldan et al, 1997, early August pre-‐harvest intercropping of a kale, rape and turnip was planted in chile peppers. Yields were reduced only 1 of 3 years and the additional forage was used for livestock allowed to graze after the chilis were harvested.
Bromeliad (Pineapple)
Acting as nurse plants and protecting the pepper plants in Hawaii, the pepper yield was 30 to 50% higher than mono-‐crop when intercropped. The heavy rains and high winds that usually damage the pepper plants was mitigated by the stalwart pineapple. (Uriza Avila et al 2005).
Fabaceae (Legumes)
Cow Pea was found to have less insect pressure from Thrips and Aphids when interplanted with peppers.
The preceding effect was also apparent in a soybean trial with peppers. The pepper's leaf water was higher in the wind shadow of the legumes. Less desiccation and cooler moist air was apparent (Hulugalle and Willatt,1987).
The best intercrop shown was where there was reduced competition between species. Using intercropping in unused spaces in a young orchard was suggested.
Succession to Deter Disease and Pests
Whereas crop rotation is a annual plan, succession planting is within the same season on the same plant space.
Early cold season crops are followed by warm season crops, and then another planting of fall cold season crops are planted at the end of the summer.
35
This relatively rapid succession reduces pest and disease opportunities. In addition to spatial diversity of the garden plan, using various plants over time also diminished pest resources and habitat.
Example:
• Spring,Frost Tolerant, Mustard Family o Cold temp plants, Radishes, Kohlrabi, Turnips o Lettuce
• Summer, Nightshade Family o Warm temp plants, Tomatoes, Peppers o Squash
• Fall, Frost Tolerant, Goosefoot Family o Cold tolerant plants, Beets, Spinach, and Chard o Broccoli
Plant Spacing and Diversity for Interplanted Relays
Intercropping is placing a diversity of plants in close proximity. Although the most popular is to plant a secondary crop between the rows of a main crop, small less mechanized plots can have increased diversity by interplanting many types of plants in a non-‐liner fashion. Fast growing species can be harvested as slower species need room to grow. In inter-‐planted successions, family groups should be kept intact using various cultivars with differing growth characteristics. As an example, Micro-‐greens, Bib lettuce, or leaf lettuce can be planted between the slower endive or escarole. 1
Intercropping is an agricultural practice that has been used for thousands of years and was only recently replaced with machinery and chemical use in the 1940s.
In winter cropping, the same rotations need to be applied to ensure soil fertility and limited over wintering of pests and disease.
Some intercropped plants use more N, but legume and other nitrogen fixing crops increase N in the soil. Intercropped fields also have lass crop damage from disease and insects. Intercropping can use up more soil resources in poor soil conditions. If the secondary crop is a nurse crop, one used to buffer the main crop from environmental extremes, and left to increase soil stability , organic material and nutrients, the soil will improved while the main crop is harvested. 3
A combination of intercropping and relay cropping partitions the soil as roots of the two plant species have differing characteristics. (Andrews and Kassman, 1976) Relay planting so plants needs are asynchronous reduces interspecific competition.
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Winter "Dormant" or Weather Protected Harvests
The big four of cold-‐hardy vegetables: mache (lambs lettuce), spinach, kale, and cabbage. When given sturdy protection from ice, snow and cold winds, survive temperatures as low as 10°F (-‐12°C).
None of the vegetables grown can withstand very cold temperatures (sub-‐freezing) for a long period of time. However, the ones listed below can withstand freezing temperatures for a short period of time. It is not possible to predict a specific vegetable tolerates a specific temperature for a specific number of hours, there are too many variables.
The Plants
Cold Tolerant Crops
Source: http://www.coldclimategardening.com/cold-climate/best-of-the-hardiest/
Plant Hardy to Notes
Arugula 15F/-9C Holds up reasonably well to rain
Beets 20F/-7C Can go colder with mulch
Broccolii 25F/-4C (?) Rain will probably kill it before the frost does
Brocolli overwintered 10F/-12C these are the biennial sprouting broccolis
Brussels Sprouts 0F/-16C Seriously, these taste nothing like the store-bought ones
Cabbage (for winter)
5F/-14C (hardiest varieties)
I haven't grown the spring cabbages like First Early Market, so I really don't know the timing
Carrots 15F/-9C
With mulch, these can be depended on to overwinter. An August 1st sowing still give useable, but smaller, roots. With carrots there seems to be big differences that are just related to how particular varieties grow as the days get shorter.
Cauliflower 25F/-4C (?) Rain and slugs tend to do mine in before the cold does
Cauliflower overwintered 5F/-15C
Takes soggy soil somewhat better than sprouting broccoli
Chard 20F/-7C Even if the plant dies back, often the crown survives to regrow in the Spring
Claytonia/Miner's Lettuce At least 11F/-12C Fast growing, compact, does well under cover
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Corn Salad/Mache At least 8F/-13C Seems to thrive unprotected in our rainy wet winters
Cress, Garden (Upland) At least 15F/-9C
Biennial plants can be started as early as late spring
Escarole/Endive Reportedly 5F/-15C
Good cloche candidate, since wetness is more of a problem than cold. Bitterness decreases with frost, and varies from variety to variety.
Favas 10F/-12C
I sow in late September. I've gotten away with sowing them in November; they will grow a little even in winter, during any spells when temps are above freezing!
Kale At least 8F/-13C Needs no protection
Kohlrabi 15F/-9C Can go lower with mulch or under cover
Garlic At least 8F/-13C I plant in late September. Basically, if the ground isn't frozen, you can put them in.
Leeks At least 8F/-13C
Big differences between varieties in terms of hardiness and bolting date. This entry reflects my experiences with Durabel.
Lettuce 24F/-4C Another good cloche candidate
Minutina ~ 15F/-10C Unusual, almost succulent leaves
Mustard 15F/-9C Hardiness is variable, depending on variety
Onions 0F/-18C
Most overwintered onions dry down in June. Waterlogged winter soils can be a problem for all overwintered onions
Onions, Walla Walla sweet Reportedly -10F/-24C Walla Wallas dry down in July.
Scallions At least 10F/-12C
This applies to Allium cepa types of scallions. A. fistulosum types are much hardier and non-bulbing, but also are less tender and hotter in flavor.
Parsnip At least 8F/-13C It's fun trying to keep these seeds damp until they sprout!
Radicchio Reportedly 5F/-15C Leaf types are easier and more reliable. Don't dawdle in sowing this one!
Radishes Uncertain
Various rots and soil dwellers spoil mine by midwinter, even though the plants are still alive
Spinach At least 8F/-13C Under a cloche they can be depended on to overwinter
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VERY COLD HARDY
In general, these are the vegetables that can be planted 4 to 6 weeks prior to our average frost-‐free date. they are termed, "Very Cold Hardy"
o Asparagus o Collards o Endive
o Kale o Kohlrabi o Lettuce
Sample listings from High Mowing Seed Co.:
Organic Brussels Winter Chervil - Winter hardy plants for early salad greens or for the herb garden. Chervil has flat, light green and lacy leaves, with a flavor somewhere between parsley and anise. The plant strongly resembles parsley and is often referred to as "gourmet parsley". It is considered one of the classic French "herbes fines". Brussels Winter is the European standard and very winter hardy. Direct seed in early spring for summer crop or fall for spring crop. Sow seeds ½-1" deep. Grow as baby leaf or full size using 6 seeds/ft in rows 12-18" apart. Hardy annual 12,800 seeds/oz(Anthriscus cerefolium) HMS
Organic Winter Density Lettuce - Heat and frost tolerant for an all season selection. Winter Density has dark green leaves and heads averaging 9-10" tall. Heads are tightly folded and rounded in when mature and sit high on the stem. Texture is a cross between a butterhead and a romaine with good flavor throughout the season. Requires cool temperature for germination.(Lactuca sativa) HMS
Organic Sorrel - Sorrel is best known for its tangy leafy greens, which are commonly used in soups and stews, in salad, or as a braising green. This cold tolerant leafy green is becoming increasingly popular as an over-wintered gourmet spring green. Leaves are bright green and slender with long petioles. Full-size leaves grow to 8" long. Plants can be harvested all season long but are best sown in late summer for harvest in early spring when most tender and mild. Grow as a baby leaf or for full size leaves. Direct sow as soon as soil can be worked or start transplants in March. Sow seeds ¼" deep, plant spacing is 8" in 12-18" rows. Plant after danger of frost has passed. Dead-head seed stalks to encourage more leaves. Perennial 34M seeds/oz (Rumex acetosa) HMS
o Mustard o Onion (from seed and sets) o Bunching Onions, OW o Peas o Potatoes o Rhubarb
o Rutabaga o Salsify o Spinach
Giant Winter Spinach, OW o Turnip
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FROST-TOLERANT
These are the vegetables that can withstand light frosts and can be planted 2-3 weeks before your average frost-free date.
o Beets o Broccoli HMS: Organic Santee F1 Hybrid Sprouting Broccoli - Also known as "broccolini" due to its appearance of minibroccoli heads atop leafy stalks. Abundant purple spears are tender, flavorful and packed with broccoli nutrients. Unlike most sprouting broccolis, Santee does not require cold treatment to initiate bud development. Becky Grube, UNH Extension, performed an over-wintering trial of sprouting broccoli in high tunnels and had impressive marketable yields as a late winter crop – perfect for late winter CSAs. (Brassica oleracea var italica)
o Brussels Sprouts o Cabbage o Carrots o Cauliflower o Celeriac o Celery
o Chard o Chinese Cabbage o Jerusalem Artichokes o Onion (from plants) o Parsnip o Radish
Garden Design
Slope, Aspect and Garden Placement
A level field is the dream of most gardeners. I agree with the exception of any perennial or orchard design where water is moved or collected in swales. An annual garden is easier to work on level ground. Terracing to achieve this also has heat-collecting benefits if the aspect of the hill is south. South facing or southern proximity to structures as written above will extend seasons via reflected heat and radiant heat. Walls or terrace faces will collect heat much like a masonry building. Large stones do the same.
It is important to place the garden close to the residence for access and also for more frequent interactions. The kitchen garden is right outside the door or perhaps on two sides of the sidewalk to the garage. The garden benefits from the close proximity to the steward, the thermal of the house, and possibly the single biggest water source, the roof ( with the use of large rain barrels or a tank)..
40
Human Centric Concepts
The definition of gardens in popular gardening is the rigid grid of straight rows and aisles of bare soil. The memory of farm machinery and emulation of the olds ways of generation gone by, at least in the pattern, persists with many people. They slave to the standard expectations of seed packet instructions and culture. When a garden is planted, all ecological and environmental components are displaced. Where as we infiltrate our natural surroundings with all our influence and cultural expectations, residential landscaping be one way, the garden is totally human centric and the gardener should be in the center of it at all times. As the main livestock and steward of the plot, the planting, management and harvesting should be as easy as possible within ergonomic limitations. The garden should be planted around the gardener until the reach is exceeded. Then the gardener can move to a new plot and begin again without stooping and shuffling across already compacted soil.
Containing the gardener within the center saves the soil on the surrounding bed for the organisms that occupy the space. Planting is managed through close interaction, with all plants over the span of the growing season. The scheme for planting can also change as the interplanted relays mature. Frequently harvested micro-‐greens or radishes are at the center and where most of the activity takes place. Larger plants are on the exterior as are plants with longer lifecycles. Cabbage, Broccoli, Cauliflower and Parsnips are relegated to the outer ring. Bush beans grow at the entrance of the outer ring while carrots, chives, and smaller plants fill the spaces.
Like a painter’s pallet, the garden is planned by the ecological characteristics of the plants and the interaction of the gardener. Relays, intercropping, rotations are easier to manage. Using the knowledge of climate, plant interactions, succession, size, ecological functions, days to harvest and zones for plant selection, growing more food in less space with less energy brings a double yield.
Resource Partitioning
Using interplanting, relays, and rotations partition the resources and allow resources to rebuild
through ecological processes 1. Partitioning separates the extraction of minerals over time and
space. Planting diverse species in patches rater than rows creates a dynamic response from soil
organisms and pests.
41
Spatial planting regimes affect the use of resources and the lifecycles of pest insects. In each
column below is a planting pattern. Monoculture, Interplanting, and Diverse Patch planting.
Imagine the lower row of graphics being the paths of insect pests, nutrient extraction, or
competition. As plants are disbursed and mixed, from left to right, in the top row, the
monoculture effects are broken up.
Temporal planting regimes create a partitioning effect over time, rotating plants in and out based
on cold tolerance, harvest days, and growth stages. Well planned relay-‐rotations increase the
aggregate yield for a garden plot. Individual monocrop yields are reduced, but combined vegetative
harvests increase. Soil organisms benefit from the mixed sources of organic material and habitat.
42
Species Form Ht x W Root Uses & Functions:
Spacing # plts
1 Tomato (A) UR 36X36 FibDp APR c Fung 30 3
2 Basil UR 18x12 FibSh Fla APC 10 4
3 Borage Mound 24x18 Tap APR INS 16 2
4 Collard c UR 36x10 Tap APRa 10 2
5 Sea Kale (A)
UR 30x18 FibDp Ins Mulch SB 16 2
6 Peppers UR 14x16 Fib INC 12 2
7 Nasturtium Mound 14x12 Rhizome APR 8 20
8 Onions UR 24x9 FibSh APC Fung 9 6
10a Comphrey UR 30x48 Tap CB DA INC INS 24”/3’ 8
10b Asparagus UR 54x24 Tap 10’ MenCi 24” 12
9 Cilantro UR 24x18 Tap INS INC NP 24 8
Polyculture Purposes / Functions / General Description & Concept:
This Salsa Garden has an interconnected group of plants.
43
Tomato is part of the campatible plants of the Nightshade family. Brassicas should not be mixed the Nightshade family. Plants cross benfit from Fungicide, Aromatic Repellents and Confusers. Resource is partitioned via shallow, deep fiberous, rhizome and tap roots.
Patch Conditions (soil, moisture, light, successional stage, disturbance regime, etc):
Moderate Soil Moisture, Direct Sun Light, Annual Garden with rotated crops and perennial beneficial plants.
Abbbreviations for ecological functions: APR-aromatic pest repellent, APC- aromatic pest confuser, INS-insecticide, NemCi- Nematodical, CB-Chem Barrier, Fung- Fungicide, DA- Dynamic Accu., NP-Nurse Plant, Fib-Fibrerous, Sha-Shallow, Dp-Deep, Tap-TapRoot
In guides to
planting
spaces the
plans rarely
exhibit the
inter-‐
cropping
possibilities.
Large spaces
are left
unused
(bare soil)
while plants
slowly grow
into them. The chart above disregards interplanting and the little boxes appear to be a guide as to
the pattern that should be used.
When working with established lists you can make a selection list of ecological analogs, similar plant cultivars, tested for hardiness. Carrot, Radish, Lettuce Cauliflower
44
Two Early Cool Season Crops Seeded - ex. Carrots and Radishes
Second Season Crop Transplanted – Lettuce
45
First Crop Harvested - Radishes
Lettuce allowed to grow Lettuce harvested and replaced with Cauliflower transplants.
46
Carrots harvested making room for Cauliflower
Cauliflower harvested and space planted with winter cover crop. Spinach or Mache, Purslane,
Claytonia, corn salad
47
References:
1. Vegetable Rotations, Successions and Intercropping by Roland Roberts, Texas Ag Extension (http://lubbock.tamu.edu/horticulture/docs/vegrote.html)
2 The role of crop rotations in determining soil structure and crop growth conditions B. C. Ball1, I. Bingham2, R. M. Rees1, C. A.Watson2, and A. Litterick2 SAC Crop and Soil Research Group, 1Bush Estate, Penicuik, Midlothian, UK EH26 0PH; and 2Craibstone Estate, Aberdeen, UK AB21 9YA. Received 23 December 2004, accepted 13 July 2005. 3. Increasing sustainability by intercropping.Author(s) Coolman, R.M.; Hoyt, G.D.Source HortTechnology.Issue 3Page(s) 309-‐312: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&CSC=Y&NEWS=N&PAGE=fulltext&D=agra4&AN=IND20371117
4. Changes in Soil Temperature Affected by the Application of Plastic Row Covers in Field Production of Lettuce and Waterlmelon
5. Overwintering And Early Production Of Salad Crops, Cerne, M., Acta horticulturae. July 1994. (371). p. 327-‐330.
6.Production Guide for Organic Carrots for Processing 2011, NYS IPM Publication No. 133 v2
7. CGM, Canola Growers Manual, Chapter Effects of Moisture and Chapter 5, Temperature, Frost, Hail, (http://www.canolacouncil.org/contents5.aspx)
8. Season Extension Techniques for Vegetable Grops. Roddy, Elaine, Ontario Minsitry of Agriculture, Food and Rural Affairs (http://www.omafra.gov.on.ca/english/crops/hort/Season_Extension.htm)
9. Effects of Foating Ro Covers on Radishes, Yellow Spanish Oniosn, Cabbage, Cucumber, Winter Squash and Sweet Corn in Redmond, Oregon in 1986. Nelson, L.J., Young, M.
10. Using Transplants in Vegetable Production Pub# 8013, Schader, Wayne L., UCLA, Divison of Agriculture and NaturalResources
11. Garden Strategies for Short Season, High Latitude Zones, Bulletin #859, Love, Noble, & Parkinson, University of Idaho Extension.
12. Yields and economics of high tunnels for production of warm-‐season vegetable crops. HortTechnology. 2003 Apr-‐June. 13(2) p. 339-‐343. Choosing and Growing Adapted Vegetable Varieties 13. Intercropping for field production of peppers, Kahn. (2010).. HortTechnology, 20(3), 530-‐53 14. Nehemiah Stone, Thermal Performance of Straw Bale Wall Systems, Ecological Building Network (EBNet) October 2003 www.ecobuildnetwork.org
Elliot Coleman Materials: Four Season Tools – Crop Rotations with Moveable High Tunnels, Smallfarmtools.com
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Winter Harvest Handbook – Chelsea Green publishing 1992 Endless Harvest, Mother Earth News, March 2000, Four Season Harvest – Chelsea Green Publishing 2009
Growing cool-‐season vegetables. Bulletin -‐ Wyoming University, Cooperative Extension Service. June 1991. (942.56)
Green house project: sustainable agriculture in urban areas.
Sustainable Agriculture Research and Education (SARE) research projects. Northeast Region. Sustainable Agriculture Research and Education (SARE) research projects. Northeast Region.. 2003, PROJECT LNE99-‐128.
Green house project: sustainable agriculture in urban areas.Author(s) Coolman, R.M., Sustainable Agriculture Research and Education (SARE) research projects. Northeast Region.: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&CSC=Y&NEWS=N&PAGE=fulltext&D=agra6&AN=IND43735826
Growing cool-‐season vegetables.Author(s) Legg, D.E.; Cook, J.Source Bulletin -‐ Wyoming University, Cooperative Extension Service.: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&CSC=Y&NEWS=N&PAGE=fulltext&D=agra4&AN=IND92048075 (www.urbanext.uiuc.edu/veggies/.)
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Using Growing Degree Days to Predict Plant Stages by Perry Miller, Will Lanier and Stu Brand (http://ipm.montana.edu/training/PMT/2006/mt200103.pdf.)
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Spinach Cultivar Trial in A 3-‐Seaon Haygrove Tunnel. Knewtson, S., Vasey, T., Dept. of Horticulture, Kansas State University (http://printfu.org/read/spinach-‐variety-‐trial-‐2005-‐ec10.html?f=1qeYpurpn6Wih-‐SUpOGumKunh7_f39PVy82Q6Mrg3cvp5oXg4d_G4IiXoKKekK_Zr5-‐fjuPqh6_bn6Gjo5De2-‐jh0ty_xsrgzYer5aOfrojbj6DfqaudrorN5ObZqKOV7OTcmtffzNzc2t7gztrnlOTfzJu_uquju9XZ4MrR3Knq2dnV5dfXyNrO0d7A09aU5dHLjqrz)
Extending the Garden Season, Babara Larson, UW Garden Fact Sheet-‐Extension Kenosha County, June 2006
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Frost hardiness of Asparagus officinalis L. , Arora, R. Wisniewski, M.E. Makus, D.J. , HortScience : a publication of the American Society for Horticultural Science. July 1992. 27(7) p. 823-‐824.
Growing small-‐fruit crops in short-‐season gardens , Love, Stephen L. Fallahi, Esmaeil Noble, Kathy. [Moscow, Idaho] : University of Idaho Extension, c2009. Bulletin ; 868 Short-‐season, high-‐altitude gardening.
Seeding Rate and Planting Arrangement Effects on Growth and Weed Suppression of a Legume-‐Oat Cover Crop for Organic Vegetable Systems . Eric B. Brennan, Nathan S. Boyd, Richard F. Smith and Phil Foster, Agronomy Journal 2009 101: 4: 979-‐988
Gardening Strategies for Short-‐Season, High-‐Altitude Zones University of Idaho 1. Growing Small-‐Fruit Crops in Short-‐Season Gardens 2. Growing Tomatoes in Cool, Short-‐Season Locations 3. Growing Tree Fruits in Short-‐Season Gardens 4. Hardy Roses for Harsh Climates 5. Herbaceous Ornamentals: Annuals, Perennials, and Ornamental Grasses 6. Introduction to Short-‐Season Gardening in Idaho 7. Managing Soils in Short-‐Season, High-‐Altitude Zones 8. Selecting, Planting, and Caring for Trees, Shrubs, and Vines
