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Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon Tom Cook OSU Horticulture Dept. 2008

Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

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Page 1: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Turf Adaptation & EcologyPart 2: Turf communities in Western Oregon

Tom Cook OSU Horticulture Dept.

2008

Page 2: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Turf adaptation implies that commonly planted grasses have specific climatic conditions inwhich they thrive. Therefore, if we know the climate we should be able to predict what grasses will have a reasonable chance to prosper. The converse is also true. If we plant grasses in climates where they are not adapted, we can expect to have problems growing a healthy lawn. One way to depict turf adaptation is through maps. Authors have long drawn maps of the USA that carve up the country into zones or regions that define both the climate and the best adapted grasses. Earlymaps were simple and divided the country up into cool season and warm season areas. Where the two basic regions intersected was a fuzzy zone generally referred to as the transition zone.

Over time maps have become more intricate and somewhat standardized in their depiction of the important climatic zones. What follows is my interpretation of general climatic regions in the USA asthey relate to grass adaptation. I have created a new zone that is not commonly found in most textbooks. What I call the Pacific Coastal region has historically been lumped in with the Cool Humid region. My reason for separating it into its own region should become clear as you study the threeslides following the generalized map of the USA.

Maps that depict zones of grass adaptation have obvious limitations. A generalized map cannot account for all of the microclimate areas in a zone. It also cannot account for climatic changes associated with changes in altitude. An example is Hawaii where the climate at sea level can beeither Warm Arid or Warm Humid depending on which side of the islands you are on. On one island, the climate can change to Cool Humid as you drive up into the mountains. The key is to use maps as general conceptual guides to zones of adaptation and realize that there will be many exceptions in any given region. Maps can only give you a very general notion of regions.

Note on the following map that humidity and rainfall changes from high in the Pacific Coastal zone to very low in the Cool Arid zone. As you move east the humidity begins to increase along with summer rainfall so that in the Cool Humid zone you have high humidity and fairly consistent summer rainfall. A similar process occurs from the Warm Arid to the Warm Humid zones.

Page 3: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Approximate zones of turfgrass adaptation in the lower 48 states

Cool Arid, Semi-arid regionCool Season grasses

Pacific Coastal Region, Cool Season grasses

Cool Humid RegionCool Season grasses

Warm Humid RegionWarm Season grasses

Warm Arid, Semi-arid RegionWarm Season grasses

Transition ZoneCool and Warm Season grassesSee references at the end of this slide show for

credits and additional information regarding the maps.

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The Pacific Coastal region, the Cool Arid/Semi Arid region, and the Cool Humid region can be compared on the basis of precipitation patterns, average monthly high temperatures, and average monthly low temperatures.

Precipitation patterns: Study the following slide and you will see the differences in both quantity andmonthly distribution of precipitation in these three zones. Most notable is that while the total precipitation in the Pacific Coastal zone is high, it is actually very dry during summer and very wet in winter. This alone separates it from the Cool Humid region where summer rainfall is the norm. It is possible to have functional turf in parts of the Cool Humid region in most years even without regular irrigation. In the Pacific Coastal region grass will only be green in summer if it receives regular irrigation.

Average monthly high temperatures: The second slide in this series shows the average monthly high temperatures for the three cool season regions. Note that there is not a lot of difference between monthly highs for the three regions during the summer period. Likewise the Cool Arid and Cool Humid regions have very similar winter high temperatures. The Pacific Coastal region again stands out because it has notably warmer winter high temperatures than the other regions.

Average monthly low temperatures: The third slide in this series shows the average monthly low temperatures for the three cool season regions. Again note the similarities between average low temperatures in winter between the Cool Arid and Cool Humid regions. The Pacific Coastal region stands out because the average low temperatures in winter are considerably higher than the other regions. You will also see that the average low temperatures in the Cool Humid region are notably higher than those in the Cool Arid region. This probably reflects greater radiation cooling in the Cool Arid region. This is especially pronounced in high desert areas of the Cool Arid region where night temperatures even in summer can drop near freezing.

Note: The graphs depicted in these slides are based on monthly values averaged over several key citieswithin each region. For example the Pacific Coastal region values are the average of Seattle, Portland,Salem, and Corvallis.

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30 year ave. precipitation patterns in Cool Season Regions

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30 year ave. HIGH temperatures in Cool Season Regions

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30 year ave. LOW temperatures in Cool Season Regions

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Once you get a feel for the basic differences in climatic regions you can begin to make sense out of turfgrass adaptation in each region.

Cool Humid: Grasses in this region are subject to freezing winters and fairly warm humid summers. The cool humid region tends to have four distinct seasons with short springs and long summers followed by nice crisp fall weather before entering into long and often cold winters. Grasses go dormant in winterfollowed by a green up period and a flush of growth in spring. Summer is a stress period with often excessive heat that causes root system dieback. Summer rainfall and high humidity leave grasses open to significant summer disease pressure. Insect pressure is significant in most years. The actual period for optimum growth can be as short as 4 months in this region. The rest of the year the grass is under either heat, drought, or cold stress.

Key grasses here include Ky. bluegrass, perennial ryegrass, fine fescues, tall fescue, with creepingbentgrass being widely used on golf courses. Annual bluegrass is also common on golf courses but isgenerally considered a weed because it often dies from the many stresses it encounters. Disease and insect resistance are important considerations when selecting grasses here. Crabgrass and other summer annual grasses are consistent problems throughout the region.

Cool Arid: For the most part turf can only be grown in this region if supplemental irrigation water is used. With water, this is a fairly easy region to grow cool season grasses. In general, winters are coldwith variable snow cover. Desiccation injury is probably more important than cold injury in most winters.Summers, while often very hot, are moderated in high elevations by cool night temperatures and in general by low humidity. Spring is short and falls tend to be clear and crisp. The low precipitationyear around and the low humidity in summer really separate this area from the cool humid region.

Key grasses here are the same as the Cool Humid region. Ky. bluegrass, fine fescue, and tall fescue allthrive here. Perennial ryegrass does well but may be prone to cold or desiccation injury in winter. Creeping bentgrass is common on golf courses and annual bluegrass is a major climax species on oldergolf courses. Buffalograss, a cold hardy warm season grass can be grown in eastern parts of this region.Disease, insect and weed pressure are generally lower than in the Cool Humid region.

Page 9: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Pacific Coastal (Western Oregon):The Pacific Coastal region is distinctively different from either the Cool Humid or Cool Arid regions. A typical growing season here is long and less well defined than in the other regions. In a normal year, grass is green for 12 months and is actively growing for 10 months. It is not unusual for grass to be cut all year long. Spring generally starts in February and continues to June. Summer runs from mid-June to mid-Sept and fall lasts often through November. Generally, during summer, night temperatures cool down significantly even when daytime temperatures are high. Humidity is inter-mediate between the Cool Humid region and the Cool Arid region. Diseases are more likely to be a problem in winter than in summer, and insect pressure is mild compared to other regions. Annual weedy grasses occur but are not consistent problems. Lawns can survive without irrigation in most years, butthey will be dormant all summer.

The grasses used in the Cool Humid and Cool Arid regions are commonly planted in the Pacific Coastalregion, but tend not to dominate lawns for long. In fact most are replaced rapidly by naturalized grasses that persist and compete better over time. I divide grasses for this area into the commonly planted grasses and the climax grasses which eventually dominate lawns.

Commonly planted grasses include perennial ryegrass, fine fescues, and tall fescue. Creeping bentgrass is planted on greens, tees, and fairways at golf courses and colonial bentgrass is often planted on tees and fairways. Ky. bluegrass has historically not performed well in this region and is rarely planted.

Climax grasses include colonial, dryland, and/or creeping bentgrass, roughstalk bluegrass, annual bluegrass, velvetgrass, and rat-tail fescue. A typical irrigated lawn in the Pacific Coastal region will contain most or all of these grasses plus remnants of the planted grasses once conversion has occurred.Non irrigated lawns will often devolve into bentgrasses and rat-tail fescue. Rat-tail fescue has a unique niche because it is a winter annual that germinates in late fall grows through winter and dies after setting seed in early summer.

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Oregon

See references at the end of this slide show for credits and additional information regarding the maps.

The obvious dividing line in Oregon is the CascadeMountain range. This map image clearly shows thatWestern Oregon is distinctly different from Central and eastern Oregon

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Pacific CoastalRegion

Cool Arid Region

See references at the end of this slide show for credits and additional information regarding the maps.

The Pacific Coastal Region is defined by winter rains, summer drought,medium to high humidity, and moderate to mild temperatures. Grass stays green during winter and requires irrigation in summer to stay green.

Page 12: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

The Pacific Coastal Region:

Grasses grow year around here and generally stay green all winter. Lawns cannot stay green in summer without supplemental irrigation.

Planted grasses: Perennial ryegrass, fine fescues, tall fescue

Climax grasses: Bentgrasses, rough bluegrass, annual bluegrass,velvetgrass, rat-tail fescue

Insects: European Crane fly, Billbugs, Black cutworm

Diseases: Red thread, Leaf spots, Rust, Fusarium Patch,Take-all Patch

Weeds: False dandelion, Common dandelion, Clovers, Mousear chickweed, Black medic,moss, others.

Page 13: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

“ All lawns transition from planted grasses to situation specific climax vegetation”

or

What you plant is not what you get!

Pacific Coastal RegionLawn Ecology

This reality is what makes the Pacific Coastal Region so unique. In most other parts of the northern USA, when you plant a lawn, you will end up with the grass you planted. If other grasses are present, you got bad seed or you importedan undesirable grass with the soil you used to construct the lawn. In our area, it doesn’t matter what you do, you will endup with other grasses invading and likely dominating the site.

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Pacific Coastal RegionClimax Species

vAgrostis sp. BentgrassesvPoa trivialis Rough BluegrassvPoa annua Annual BluegrassvHolcus lanatus VelvetgrassvVulpia myuros Rat-tail FescuevPlanted grassesvVarious moss speciesvNumerous dicot species

Page 15: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Bentgrass

T Cook photo

Creeping, colonial, and dryland bentgrass are all part of the soil seed bankand are well adapted to wet winters and summer drought or summer irrigation.They can produce dense turf with very little fertilizer nitrogen. They are the most competitive grasses under moderately low input conditions. Most older lawns have significant amounts of bentgrass in them.

Page 16: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Velvetgrass

T Cook photo

Velvetgrass can be found throughout the Pacific Coastal Region and is very common in coastal lawns where it is often as the dominant component. I find it in most lawns in the Willamette Valley though occasionally it is absent. This isn’t a very pretty grass but it is tough and handles both wet and dry soils.

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Poa trivialis

T Cook photo

Roughstalk bluegrass is common throughout the entire Pacific Coastal Region. It is mostactive in winter when it grows more vigorously than all other grasses. It handles wet soilsvery well and spreads via stolons. In the spring it gets very coarse and stemmy when it moves into flower mode. It struggles in heat and drought but survives all stresses. It is amajor component of the soil seed bank and is a common contaminant in seed mixes, so it can be found in almost all lawns.

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Annual bluegrass

T Cook photo

Annual bluegrass is ubiquitous in the Pacific Coastal Region. It often shows up in new lawns thatare planted late in the fall. It is a major component of all old golf courses and produces greatputting turf. In homelawns, it generally dominates lawns that are over watered and over fertilized.It is a prolific seed producer and is a major part of the soil seed bank. It is least likely to be a significant component in old bentgrass lawns that are unfertilized and sparingly watered.

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December after germination

July after death

T Cook photos

Rat-tail fescueVulpia myuros

Rat-tail fescue is a true winter annual with a special niche in lawns that receive no irrigation at all. It is a beautiful grass that germinateswith the onset of fall rains, grows through winter, flowers in spring and dies in June. It is perfectly suited to our Mediterranean climate.

Rat-tail fescue has increased significantly inrecent years as more people have quit irrigatingtheir lawns. As the perennial grasses thin outor die, this grass is perfectly suited to fill the void.

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Where do climax grasses come from?

Ø Contaminated seed or sodeg. Poa trivialis or bentgrass in P rye

Ø Persistent soil seed bankeg. Poa trivialis Roughstalk bluegrass

Poa annua Annual bluegrassAgrostis BentgrassesHolcus Velvetgrass

Vulpia Rat-tail fescue

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Lawn Moss

T Cook photos

Mosses also have a special niche in Pacific Coastal lawns. They grow well where other plants can’t growand are well suited to infertile soils, shady sites and wet soils. They require no fertilizer and can survive drought by simply drying up. As soon as the fall rains return, dried plant fragments green up and grow all winter. In general, the wetter the winter the more vigorous the moss.

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False dandelion

Mousear Chickweed

White cloverEnglish daisy

Black medic

False dandelion

T Cook photos

Unless herbicides are used to control them, there will always be a variety of dicot plants in lawns. They all are adapted to drought, low fertility, fall germination cycles, etc., which makes them competitiveand persistent. Many dicots are very compatible with grass and help create a stable mix of ground covers generally in low input lawns.

Black medic

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A Species Rich Climax Lawn

T Cook photo

This is a perfect example of a climax lawn growing in shade on a fairly wet infertile site. The grasses include mostly bentgrass and roughstalk bluegrass. The dicots include white clover and speedwell (Veronica filiformis). With regular mowing, this lawn will sustain itself for a very long time with only periodic watering in summer.

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New perennial ryegrass sod lawn in Seattle, WAT Cook photo

When you plant a straight perennial ryegrass lawn, it initially is pure with no apparent contaminants.If the site is clean, it will stay pure for at least a few years, but eventually other grasses will move in.

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Young commercial site planted to 100% perennial ryegrass

Poa trivialis

Holcus lanatus

T Cook photos

Seeded lawns often develop contaminants within a year of planting. Initially contaminants come fromthe soil seed bank. Another source it dirty seed. On this site there was a fair amount of velvetgrassand roughstalk bluegrass on the site. I also found quite a bit of bentgrass. It won’t take long for this lawn to convert to the climax grasses.

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Ryegrass to bentgrass conversion2 yrs 3 yrs

5 yrs6+ yrs

T Cook photos

These photos show the progression from a few isolated spots to total domination in just a few short years. This happens to almost all lawns in the Pacific Coastal Region.

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10 yr old climax lawn in Seattle

T Cook photo

Climax lawns are often very nice lawns. They are persistent, require very little fertilizer, look nice when irrigated regularly, and survive quite well without irrigation by going dormant.

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60+ yr old climax lawn in Seattle

T Cook photo

This beautiful lawn is almost solid bentgrass.

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“ The primary selective pressurein the Pacific Coastal region may be the lack of environmentalextremes”

orEverything grows but nothing dominates

In much of the northern USA, conditions are generally unfavorable for lawn grasses. The combination of hot humid summers and cold miserable winters mean that only the toughest grasses can survive. Generally, if you plant one of the adapted grasses and provide appropriate maintenance, the lawn will stay fairly pure.

In the Pacific Coastal Region, our mild weather is suited to nearly every cool season grass. Tolerance of grasses to extreme temperatures is of minor importance. Grasses that would appear to be relatively weak often do very well here. The result is a sort of ‘free for all’ in which everything grows at some time of the year but no one grass dominates in all situations. The average lawn will have anywhere from three to six different grasses along with numerous broadleaf plants.

Page 30: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Pacific Coastal Lawn Ecology Rule # 1

Plants that grow well fall through spring or at least maintain density, will eventually dominate the stand.

or

“Competition occurs in the cool months”

In the most common scenario that I see, grasses like bentgrass, annual bluegrass, and roughstalk bluegrass tend to showup in new lawns during the first winter after planting. Depending on intensity of maintenance, one or more of these will spread and begin to form distinct patches. Most of their spread will occur during the nine cool months when they are morevigorous than the planted grasses. Even if they go dormant in summer, they will recover and spread during fall throughspring and will eventually dominate most lawns.

Page 31: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

T Cook photo

This Kentucky bluegrass lawn in Corvallis, Oregon was in its first winter after planting. The brown grass is the Kentucky bluegrass and the green tufts included a variety of invading speciesthat either came from the sod or were in the soil seed bank. This lawn has since converted to all climax species and I doubt if I could find any Kentucky bluegrass at all.

Page 32: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Annual bluegrass and Poa trivialis in a young ryegrass lawn.

T Cook photo

On irrigated and fertilized perennial ryegrass lawns, annual bluegrass is often the first and most successful invader. Note how well it grows in winter. One of the qualities that make annual bluegrassso competitive is the density it achieves. Add in vigorous spring flower and seed production and it will easily dominate all other grasses.

Page 33: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Climax lawn in Seattle, WAT Cook photo

When all is said and done, plan on some form of a climax lawn. Once the climax stand develops you will have a surprisingly easy lawn to maintain.

Page 34: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Bentgrass climax lawn in Lake Oswego, OR

T Cook photo

Other than regular mowing and periodic irrigation this lawn receives very little in the way of inputs.

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Bentgrass Climax

Grants Pass, OR

T Cook photo

Even as hot as it gets in Grants Pass in summer, this climax bentgrass lawn is doing just fine.

Page 36: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Qualities of Climax Lawnsin the Pacific Coastal Region

ØBetter at lower mowing heightsØColor is lighter greenØRequire less fertilizerØLimited drought resistanceØLong lived soil seed bankØStrong winter competitors

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Pacific Coastal Region Succession Rule # 2

“Maintenance intensity determines the succession endpoint”

Factors:N fertilityIrrigation intensityHerbicide use

Page 38: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Potential succession end pointsin the Pacific Coastal Region

Perennial Ryegrass

High N Low N

N responsivegrasses dominate

Low N responsive plants dominate

Annual BluegrassClimax

Bentgrass, moss, clover Climax

Irrigation and fertilization are two major factors that influence how lawns evolve. In this case, assuming the site is irrigated, fertilization practices will drive the succession to either bentgrass or to annual bluegrass. The next few slidesfollow the events that occur if the lawn is maintained under low fertility.

Page 39: Turf Adaptation & Ecology Part 2: Turf communities in Western Oregon

Why does low N ryegrass get out competed?

Brown Blight Rust

Red thread

T Cook photos

Even though perennial ryegrass is the most commonly planted grass throughout the region, it is a relativelypoor competitor over time. When under low fertility,ryegrass suffers from several diseases that tend to thin it out. When that happens, the stand is ripe for invasion bygrasses better suited to low fertility.

Brown blight, rust, and red thread rarely kill any grass but they can thin it out during fall and winter when it is not a good time to force new growth with fertilizer. If you do fertilize, it may simply be out competed by annual bluegrassor roughstalk bluegrass.

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Transitioning ryegrass lawn in Seattle

T Cook photo

We hear about the perils of over fertilizing but in truth most lawns are under fertilized. When you plant a grass like perennial ryegrass that requires regular nitrogen applications to maintain density, it will likely be invaded by species that do well with minimal fertilizer. This park lawn inSeattle is rapidly being taken over by white clover which can fix nitrogen and grow well without added fertilizer.

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English Daisies in climax ryegrass/bentgrass/Poa annua turf

T Cook photo

English daisy is a common component of lawns under low fertility and subjected to moderatedrought stress in summer. If the site is wet in winter they grow even better.

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Climax lawn in Portland, ORBentgrass/Poa annua/Poa trivialis/ Veronica climax

T Cook photo

This site is wet in winter and receives shade in the afternoon in summer. Under low fertility the lawn has evolved into a broad based mix of grasses and Veronica species. It is beautiful in spring when the blue flowers of the Veronica are out.

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Bentgrass/Poa trivialis/Clover climax Corvallis, OR

T Cook photo

This lawn has been fertilized with nitrogen on average once every 4 years. It is dominated by bentgrass and clover, with roughstalk bluegrass showing up during winter. There is very little annual bluegrass. It gets irrigated approximately once per week for most of the summer period.

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Summer drought impact

Perennial Ryegrass

Stand thins as ryegrassgoes dormant. Some plants die . Drought tolerant dicots invade.

Ryegrass standthins to clumps.

Weeds germinate in fall.

Invading dicots:Clover

False dandelionCommon yarrow

Mousear chickweed

Invading grasses:Dryland bentVelvetgrass

Rat-tail fescue

Summer drought influences both the type of broadleaf plants and the mix of grasses that dominate the site. Since over60% of the lawns in the Willamette Valley of Oregon are not irrigated regularly, drought impacts are important.

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Perennial rye clumping out Climax bent lawn in fall

Climax bent lawn in springBent rhizomes recovering

T Cook photos

Ryegrass can withstand a fair amount of drought, but when drought is too severe many individual plants die leaving openareas for invading grasses.

Bentgrass doesn’t stay green under drought. It turns brown and goes dormant very quickly. When the fall rains come, it starts to regrow and slowly fills in by the spring period as noted below.

Bentgrass recovers from crownsand rhizomes primarily.

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December after fall germination

July after death

T Cook photos

Rat-tail fescue

After many years without summer irrigation, even bentgrass stands will decline and the trend movestoward invasion by this winter annual. In some respects, Rat-tail fescue is the ultimate climax grassin unirrigated lawns. It is usually joined by False dandelion, which is our most drought tolerant broadleaf invader.

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False dandelionMousear Chickweed

White cloverEnglish daisy

Black medic

False dandelion

T Cook photos

Other broadleaf plants suited to prolonged drought include the p lants shown here.Most are good fall germinators and survive drought by seed, dormancy, orresistance.

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Bentgrass/ Rat-tail fescue/ False dandelion climax

T Cook photos

This mix of grasses and False dandelion is one of the most common climax lawnsthat I see from the Willamette Valley of Oregon to Vancouver, BC Canada.

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Low input lawns: Pacific Coastal Region

Irrigated climax:Bentgrass / Poa trivialis / clover Transition occurs in 3-10 yrs.

Non-irrigated climax:Bent./ Rat-tail fescue/ False dandelionTransition occurs in 10+ years.

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Potential succession end pointsin the Pacific Coastal Region

Perennial Ryegrass

High N Low N

N responsivegrasses dominate

Low N responsive plants dominate

Annual BluegrassClimax

Bentgrass, moss, clover Climax

Even though most lawns are maintained under low fertility, there are many sites that receive regular fertilizer and regular irrigation. Under those conditions a different sort of climax lawn emerges.

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Why does annual bluegrass dominate under high N?

Fusarium patchLeafspot

T Cook photos

Just as with low fertility, diseases play an important rolein determining which grasses dominate under higher fertility.Two important diseases include Fusarium patch and various leaf spot diseases. When these attack perennial ryegrassthey cause severe thinning typically in winter. This allows grasses like annual bluegrass to invade and take over.

Fusarium patch

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Turf thinning from high N diseasesAggressive winter growth

T Cook photo

In this photo you can see the brown and thin Kentucky bluegrass that has been riddled by leaf spot and the vigorous green annual bluegrass that is rapidly filling in. It won’t take long for the annual bluegrassto dominate.

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High N, irrigatedannual bluegrass climax

T Cook photo

This lawn has long been maintained with regular fertilizer applications and regular irrigation. It is almost 100% annual bluegrass.

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Potential Climax end points

Perennial Ryegrass

High N Low N

N responsivegrasses dominate

Low N responsive plants dominate

Annual BluegrassClimax

Bentgrass, moss, clover Climax

Typical Poa annua golf course in Portland , OR

T Cook photo

Long term consistent care will inevitably result in golf courses dominated by annual bluegrass.

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High input turf: Pacific Coastal Region

All areas transition to Poa annuawith remnants of planted grasses.

T Cook photo

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Summary:

The bottom line in the Pacific Coastal Region, which includes westernOregon, is that the commonly planted domesticated grasses such as perennial ryegrass, the fine fescues, tall fescue, and Kentucky bluegrasswill eventually be invaded by other grasses that were generally not planted. Most will also develop a resident dicot population

Which plants dominate depends on the level of fertility and the intensityof irrigation and other cultural practices. Low input irrigated lawns will often be dominated by bentgrasses, roughstalk bluegrass, and clover or other site specific dicots. Unirrigated lawns will generally be dominatedby bentgrasses, Rat-tail fescue, and False dandelion. Lawns that are irrigated and fertilized regularly will often be dominated by annual bluegrass.

To the extent they are used, herbicides will determine what if any dicotsare present, but will have little impact on the grass composition.

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References:

All maps used in this presentation were created and copyrighted by Ray Sterner at the Johns Hopkins University Applied Physics Laboratory. The maps are licensed to North Star Science and Technology, LLC from which permission was granted for use in this presentation.

Information regarding the maps and images can be located athttp:// fermi.jhuapl.edu/states/