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PHILIP RONALD, PH.D.

OPTIONS FOR SHADE TREE DIVERSITY IN WINNIPEG

THE GREEN CITY

Green Ash monoculture

A visionary desire to

green the city

Chose tough, native trees

often sourced from the

riverbanks

BUToverplanted and didn’t

envision the worst

American Elm monoculture

RESULTS OF THE PAST

Two genera = 60% of all

public trees

Winnipeg’s urban forest is vulnerable

Trees are a long-term

investment

Our climatelimits the

opportunities for diversityBreakdown by genus of 300,000 park and boulevard trees

Source: City of Winnipeg

DIVERSITY GUIDELINES

Frank Santamour’s (1990) diversity guidelines:

Plant no more than 30% of a family Aceraceae Plant no more than 20% of a genus Acer Plant no more than 10% of a species Acer platanoides

WE NEED 5 SUITABLE GENERA & 10 SUITABLE TREE SPECIES!

John Ball’s (2015) more stringent formula for diversity:

No more than 5% of a community’s trees be in a single genus

MEANS WE NEED 20 SUITABLE TREE GENERA!

From now on…

We must

Blend in diverse

species at every

opportunity

Develop master plans

for tree planting in

new neighborhoods

CAN WE GET TO 20

GENERA?12 SHADE TREE GENERA

• Acer - maple• Aesculus - buckeye• Alnus - alder• Betula - birch• Celtis - hackberry• Eleagnus - olive• Fraxinus - ash• Juglans - walnut• Phellodendron - corktree• Populus - poplar• Quercus - oak• Salix - willow• Tilia - linden• Ulmus - elm

MERIT TRIAL PLANTINGS?

• Gleditsia - honeylocust• Gymnocladus - coffeetree

6 FLOWERING TREE GENERA

• Crataegus - hawthorn• Malus - crabapple• Prunus - cherry• Pyrus - pear• Sorbus - mountain ash• Syringa - tree lilac

4 CONIFEROUS GENERA

• Larix - larch • Picea - spruce• Pinus - pine• Thuja – cedar

OTHER MINOR GENERA

• Carya - hickory• Ostrya - ironwood

BARELY!

There are 18 rel iable

deciduous tree genera

Perhaps 3-5 more possible

Some are not city -fr iendly or l imited to park

settings

More on the street testing

is needed

TREE GENERA FOR CITY OF WINNIPEG CHALLENGES TO TREES

Our trees face many abiotic

challenges

BUT

The greatest threats are

l iving

General vsspecific pests

Invasive alien species

e.g. DED, EAB

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QUESTIONS ABOUT EAB

When wil l i t arr ive in

Winnipeg?

How quick wil l we find it?

How bad wil l i t be once it arr ives?

Wil l we have any control options by

then?

Have we put a value on what

we stand to lose?

Dr. Jennifer Koch, U.S. Forest Service, Northern Research Station, Delaware, OH

TREES COME & GO

The best sell ing tree of

one generation

can disappear in the next

e.g. Siberian elm

Schuber t cherry

Swedish aspen

Tower poplar

BUT losing ash is a tough pil l

to swallowUnity sugar maple in front of dying Tower aspen - Portage la Prairie

OTHER CONCERNS

When selecting trees for urban plantings, we

want:

- ornamental features

- reduced maintenance

ELIMINATE:

Poor crowns

Aggressiveness

Root sprouts

Weediness

Fruit drop

Ussurian Pear – fruit fall

Green Ash volunteersCathedral Elm - canopy

CHALLENGE OF

URBAN SOILS

Even the right tree faces an uphill climb!

Top-soil of ten stripped

Compacted subsoil

Poor drainage

Minimal water inf i l tration

Litt le organic matter

Upper Fort Garry, Winnipeg

Same site – 1 year later

SHADE TREES

TREE-LESS STREETS?

Some streets don’t deserve

trees

The metallic tree does have

a place!

Choose tough “trees” for the

very worst sites:

Green Spires Caragana

Silverado Olive

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CATEGORIZE STREETS

Not every street is the

same

Know what we can grow in

each situation

Focus on collector/local

streets

Tree lawn width

Salt appl ication

Traf f ic levels –# of lanes

Speed l imit

ARTERIAL = High traffic

LOCAL = “Sleepy” residential street

COLLECTOR = Moderate traffic

Salt spray is a product of traffic density and speed

Ohio urban foresters Alan

Siewert & Stephanie

Miller

Tool to assess viabil ity of

planting sites

Ensures trees are planted in best sites for

long-term success

URBAN SITE INDEX

4 soil factors: • existing vegetation, surface compaction,

probe penetration & soil development

4 street factors: • speed limit, number of lanes, existence

of on-street parking, & length between traffic control devices

Planting site is rated with a number from 1 (worst) to 20 (best) Sugar maple (USI=16)

In Milwaukee, Wisconsin each residential block now has up to 4 different tree types, including

lindens, oaks, maples and hackberries.

Shortlists of appropriate

boulevard tree genera

Collector streets:

Elm

Hackberry

Tree Lilac

Local streets:

Maple

Oak

Linden

A NEW LOOK FOR STREETS

We need to move from a species monoculture to

managed spatial diversity

85 entries

Overused in many areas of North America

BUT needed in Manitoba

Hybrid vigor

Well adapted to urban sites

Cultivar:‘Regal

Celebration’

FREEMAN MAPLE

‘Regal Celebration’ – zone 2‘Sienna Glen’ – zone 4

Castleton Court, Winnipeg

3,287 entries(1 .1%)

Fast growing

Tolerates urban condit ions

Moderate salt tolerance

Chlorosis on alkaline soils

Limb breakage

Cultivar:‘Si lver Cloud’

SILVER MAPLE

Winkler, Manitoba

‘Silver Cloud’Ottawa Avenue, Winnipeg

115 entries

Excellent choice for diversity

Long-l ived, soi l adaptable

Excellent form and fal l colour

Sensit ive to salt and drought

Cult ivars:

‘ Inferno’

‘Sept. Flare’

SUGAR MAPLE

Henderson Highway, Winnipeg

‘Inferno’

‘September Flare’

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A reliable northern seed

source

Collections at the northern edge of the

eastern broadleaf

forest

Establish maternal trees

in Manitoba

LORD SELKIRK STRAIN

BUCKEYE

431 entries(0.1%)

Moderate salt tolerance

Spring panicles

Excellent form

Orange-red fal l colour

Fruit may be an issue

Cult ivar:‘Autumn

Splendor’

‘Lavaburst’‘Autumn Splendor’

Oak Street, Winnipeg

MANCHURIAN ALDER

345 entries

‘Prairie Horizon’

NDSU introduction

Drought tolerant

Unique buds and foliage

Sapsucker target

‘Prairie Horizon’

Vernon Road, Winnipeg

PAPER BIRCH

1,488 entries

(0.5%)

Native tree

White bark

Moisture sensit ive

Bronze birch borer

Cult ivar:

‘Prair ie Dream’

Stress-tolerant

Bayview Drive, Winnipeg

‘Prairie Dream’

HACKBERRY

1,213 entries(0.4%)

Tolerance to alkaline soi l and drought

Per forms well in urban sites

Salt sensit ive

Slow to establish

Storm damage

No nor thern cult ivars

‘Delta’ strain

Morden, Manitoba

Polson Ave, Winnipeg

AMUR CORKTREE

25 entries

Aromatic compound

leaves

Spongy bark

Pest free

No nor thern cult ivars

Limited nursery

availabil ityQueens Park Crescent, Winnipeg

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BUR OAK

17,125 entries (5.7%)

Drought tolerant

Long-l ived species

Transplant shock – slower

to establish

Sensit ive to soi l

disturbance

Cult ivar:‘Top Gun’

Trembley Street, Winnipeg

Portage la Prairie ‘Top Gun’NORTHERN

PIN OAK

21 entr ies

Toughest of the red oak group

Long- l ived, drought tolerant

Red fal l colour

Iron chlorosis; bud on Bur Oak

Cult ivars:

‘Shooting Star’

‘Majestic Skies’

‘Shooting Star’

‘Majestic Skies’

AMERICAN LINDEN

Excellent shade tree

Large leaves, fragrant flowers

Good grower on most sites

Salt / drought sensit ive

Avoid poorly drained sites

Cult ivar:

‘True Nor th’

Nicollet Avenue, Winnipeg

‘True North’

LITTLE LEAF LINDEN

A Manitoba luxury versus

zone 2

Medium shade tree

Dense canopy, small leaves

stay green longer

More adapted to harsh urban

sites

Cultivars:‘Golden

Cascade’‘Greenspire’

‘Golden Cascade’

‘Greenspire’

Grierson Avenue, Winnipeg

HYBRID LINDENS

‘Dropmore’American x L itt le

Leaf

‘Glenleven’American x Litt le Leaf

‘Skinur’American x Manchurian

‘Harvest Gold’Mongolian x Litt le Leaf

‘Dropmore’

‘Harvest Gold’

AMERICAN ELM

57,700 entries(19.2%)

Our best urban shade tree

Crown form, drought

tolerance

DED susceptibi l i ty

Overuse in the past

Cult ivars:‘Brandon’

‘Prair ie Expedit ion’

‘Prairie Expedition’

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JAPANESE ELM

1,455 entries(0.5%)

DED-resistant

Nearly seedless

Useful as “uti l i trees”

Can’t replace American Elm

Small stature, s lower growth

Cult ivar: ‘Discovery’

form vs. American

‘Northern Empress’ ‘Discovery’

HYBRID ELMS

24 entries

DED-resistant

Fast growing

Poor crowns on some cult ivars

Cult ivar:

‘Tr iumph’

Crown form similar to American

Traces back to Manitoba

‘Triumph’

“I am most impressed with the ascending limbs and favorable branch attachment on the majority of trees I have seen. The structure is reminiscent of the large old upright elms, with the tall broad canopy that enhances character and adds a sense of longevity to established neighborhoods.”

Jim Barborinas, Urban Forest Nursery

WORTH A TRY

Excellent tolerance to alkaline soi l ,

urban stresses

Successfully growing in

Bismarck and Fargo

Take advantage of

urban heat island

Import as larger trees

Cult ivar / seed source is

crucial

‘Northern Acclaim’ Honeylocust

Kentucky Coffeetree - PortageLinacre Road, Winnipeg

Bismarck, ND

PARK TREES

Trees that have traits that

preclude their use as

boulevard trees

Low branching

Large fruit

Shallow rooting

Moisture sensit ivity

Salt sensit ivity

WALNUT & BUTTERNUT

59 Butternut

40 Black Walnut

Unique: fol iage, fruit ,

form

Attract wildl i fe

Transplant shock: tap-root

Drought intolerant

No cult ivarsSeed source is

crucial!Gretna Bay, Winnipeg

POPLAR & WILLOW

3,804 + 12,390(5.4%)

Fast growing –over-aggressive

Salt tolerance

Shallow rooted

Avoid aspens -BLD

Poplar cult ivars:‘Prair ie Sky’‘Sundancer’

Wil low cult ivar :‘Laurel ’

‘Sundancer’ Hybrid Poplar

Cottonwood - Calgary

Laurel Willow - Winnipeg

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CONIFERS

Prefer to leave low branches

intact

Issue with winter shading

Stil l have relevance in

diversity

Winter value

Can be a part of the

diversity solution

Colorado Spruce

Swiss Stone Pine

Siberian Larch

SMALL TREES

SMALL TREES

WHY SMALL TREES?

Nothing else will fit!

Less maintenance

Easy to prune

Colourful flowers/fruit

Space in yard for several

choices

AMUR & TATARIAN

MAPLE1986 + 79

(0.7%)

‘Hot Wings’

“Traf f ic -stopper”

Outstanding red samaras - J u l y 1

to Se pte m ber 15

‘Ruby Sl ippers’

Better tree form vs ‘Hot Wings’ ,

but inferior samara colour

‘Ruby Slippers’

‘Hot Wings’

‘Hot Wings’

HAWTHORN

290 entries (0.1%)

Old Morden hybrids that

st i l l have relevance

Excellent small trees

Double-white flowers

Sparse fruit production

Cult ivars:‘Snowbird’

‘Toba’

‘Snowbird’ ‘Toba’

ROSYBLOOM CRABAPPLE

‘Gladiator’ Rosybloom

Upright form

Glossy purple foliage

Bright pink flowers

Resistant to fireblight and

scab

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FLOWERING CRABAPPLE

Evolution in form

Many older cultivars were selected with a spreading

habit

The new trend is towards

upright

‘Thunderchild’ - 1974

‘Selkirk’ - 1967

‘Royalty’‘Selkirk’

‘Thunderchild’

‘Gladiator’‘Starlite’

SPIRE ROSYBLOOM

Columnar

Slow growing

Disease-free

Potential as summer

privacy screen

‘Emerald Spire’ &

‘Purple Spire’

‘Emerald Spire’‘Purple Spire’

FLOWERING CRABAPPLE

‘Starlite’ Siberian-type

White f lowers

Tiny fruit

Green foliage

Upright form

Outstanding disease

resistance

FLOWERING CRABAPPLE

Fruit is an ornamental feature but can also be

messy

Crabapplesshould be:

Small and colourful

Retained through winter

Attractive to birds

‘Starlite’

‘Selkirk’

AMUR CHERRY

875 entries(0.3%)

Resistant to black knot

Golden exfol iating bark

Moderate salt tolerance

Issues with frost cracking

Cultivars:‘Goldspur’

‘Klondike’

‘Goldspur’

‘Klondike’

Wellington Crescent, Winnipeg

USSURIAN

PEAR

‘Navigator’Pyrus ussuriensis

100 entries

Tough tree -needs

tweaking

White blooms before leaves

Unwanted fruit

Cult ivars:‘Mountain

Frost’

‘Navigator’upright crown

less fruitDobrinsky Drive, Winnipeg

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MOUNTAIN ASH

670 entries(0.2%)

Under-rated genus

4 season value

Fire bl ight concerns

European‘Rossica’

Upright crown

ShowyNative

Round crown

‘Rossica’

Showy

TREE LILAC

2,036 entries(0.7%)

Sti l l one of the best small

trees

Ver tici l l iumissue

‘Ivory Si lk’ wasconsidered

best cv

‘Ivory Pi l lar ’Upright formClean fol iageVer tici l l ium R

‘Ivory Pillar’

STEPS FOR A MORE SUSTAINABLE URBAN FOREST

Give precedence to residential

In-plant diversity at every opportunity Keep planting and protecting

No more monocultures – its time to mix it u

QUESTIONS?