2018‐02‐15

OPTIONS FOR SHADE TREE DIVERSITY IN WINNIPEG

PHILIP RONALD, PH.D.

WINNIPEG: THE GREEN CITY

Early 1900’s: a visionary desire to green the city

American Elm monoculture Chose tough, native species (elm, ash)

Trees often sourced from the riverbanks

BUT we didn’t envision the worst case scenario Green Ash monoculture

1 2018‐02‐15

RESULTS OF THE PAST

Two genera = 60% of all public trees

Winnipeg’s urban forest is vulnerable

Trees are a long- term investment

Our climate limits the opportunities for tree diversity Breakdown by genus of 300,000 park and boulevard trees

Source: City of Winnipeg

Frank Santamour’s (1990) diversity guidelines: DIVERSITY  Plant no more than 30% of a family e.g. Aceraceae GUIDELINES  Plant no more than 20% of a genus e.g. Acer  Plant no more than 10% of a species e.g. Acer platanoides How do we WE NEED 5 SUITABLE GENERA & 10 SUITABLE TREE SPECIES! change the status quo?

From now on we must

Blend diverse species into existing monocultures at every opportunity

Develop master John Ball’s (2015) more stringent formula for diversity: plans for diverse tree plantings in  No more than 5% of a community’s trees be in a single genus new neighborhoods MEANS WE NEED 20 SUITABLE TREE GENERA!

2 2018‐02‐15

CAN WE GET TREE GENERA FOR CITY OF WINNIPEG TO 20 GENERA? 13 SHADE TREE GENERA 6 FLOWERING TREE GENERA • Acer -maple • Crataegus -hawthorn BARELY! • Aesculus -buckeye • - crabapple • Alnus -alder • Prunus -cherry There are 19 • Betula -birch • Pyrus -pear reliable • Celtis - hackberry • Sorbus - mountain ash deciduous tree • Eleagnus - olive • Syringa - tree lilac genera • Fraxinus -ash • Juglans -walnut 4 CONIFEROUS GENERA Perhaps 3-5 • Phellodendron -corktree more possible • Larix -larch • Populus -poplar • Picea -spruce • Quercus -oak Some are not • Pinus -pine • Salix - willow city-friendly or • Thuja –cedar • Tilia - linden limited to park • Ulmus -elm settings OTHER MINOR GENERA MERIT TRIAL PLANTINGS? • Carya –hickory More • Maackia – maackia “on the street” • Gleditsia -honeylocust • Ostrya - ironwood testing is • Gymnocladus -coffeetree needed

MAINTENANCE CONCERNS

In our quest for urban diversity, we must balance:

ornamental features / utility

maintenance requirements Ussurian Pear – fruit fall CONSIDERATIONS: Fruit/twig drop Poor crowns Aggressiveness Basal sprouts Suckering

Seediness Weediness Invasiveness Cathedral Elm - canopy Green Ash volunteers

3 2018‐02‐15

CHALLENGES TO TREES

Our trees face many abiotic challenges e.g. salt, drought

BUT The greatest threats are living forces

General vs specific pests

#1 concern: Invasive alien species e.g. DED, EAB

EAB ARRIVES IN WINNIPEG

EAB found in St. Boniface in December 2017

357,000 city ash trees at risk

Cost to Wpg over 10 years: $105 million $22.5m to remove $48m to replant $19.5m to protect $15m for waste

Effect on natural areas could be catastrophic

4 2018‐02‐15

RESISTANCE TO EAB

EAB resistance is a species level trait

All North American ash species are susceptible

Bioassay and garden studies show strong EAB resistance in Mancana Manchurian ash

Can we introgress EAB resistance into native ash spp. Dr. Jennifer Koch, U.S. Forest Service, Northern Research Station, Delaware, OH

IMPACT OF WINTER COLD

Could winter be Manitoba’s wildcard?

Intensity and duration of cold temperatures

Effect on larval survival

Minnesota study: 5% die @ -18 C 34% die @ -23 C 79% die @ -29 C 98% die @ -34 C

Will not eradicate but may reduce rate of spread

COLD HARDINESS OF EMERALD ASH BORER, AGRILUS PLANIPENNIS: A NEW PERSPECTIVE Robert C. Venette & Mark Abrahamson

5 2018‐02‐15

TREES COME & GO

The best selling tree of one generation can disappear in the next

e.g. Siberian elm Schubert cherry Swedish aspen Tower poplar Green/black ash

BUT losing ash is a tough pill to swallow!

We have lost most of the “easy” trees Unity sugar maple in front of dying Tower poplar - Portage la Prairie

SHADE TREES

6 2018‐02‐15

Main Street TREE-LESS STREETS?

Some streets don’t deserve trees

Maybe the metallic tree does have a place!

Choose tough species for the Portage Avenue very worst sites:

Green Spires Caragana Silverado Olive

CATEGORIZE STREETS

Not every street is the same: ARTERIAL = High traffic e.g. Pembina Traffic levels

Number of lanes

Salt application

Speed limit

Tree lawn width

COLLECTOR = Moderate traffic e.g. Ness Know what we can grow in each situation

Focus planting efforts on Salt spray is a product of collector/local traffic density and speed streets LOCAL = “Sleepy” residential street

7 2018‐02‐15

4 soil factors: • existing vegetation, surface compaction, URBAN SITE probe penetration & soil development INDEX

4 street factors: • speed limit, number of lanes, existence Ohio foresters of on-street parking & length between Alan Siewert & traffic control devices Stephanie Miller

A planting site is rated with a USI number: Simple tool to 1 (worst) to 20 (best) Sugar maple on USI=16 assess viability of urban planting sites

Ensures trees are planted in best sites for long-term success

A good planting decision can have a 100 year payback

A NEW LOOK In Milwaukee, Wisconsin each FOR STREETS residential block now has up to 4 different tree types, including lindens, oaks, maples and hackberries. Shortlists of appropriate tree genera

Collector streets: Elm Corktree Tree Lilac Buckeye We need to move from a Alder species monoculture to managed spatial diversity Local streets: Maple Linden Oak Mtn Ash

8 2018‐02‐15

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

85 entries

Overused in many areas of North America

BUT needed in Manitoba

Hybrid vigor

Well adapted to urban sites

Cultivar: ‘Regal Celebration’ Castleton Court, Winnipeg

Winkler, Manitoba SILVER MAPLE

3,287 entries (1.1%)

Fast growing

Tolerates urban conditions

Moderate salt tolerance

Chlorosis on alkaline soils

Limb breakage

Cultivar:

‘Silver Cloud’ ‘Silver Cloud’ Ottawa Avenue, Winnipeg

9 2018‐02‐15

SUGAR MAPLE

115 entries

Excellent choice for diversity

Long-lived, soil adaptable

‘Inferno’ Excellent form and fall colour

Sensitive to salt and drought

Cultivars: ‘Inferno’ ‘Sept. Flare’

Henderson Highway, Winnipeg ‘September Flare’

LORD SELKIRK SUGAR MAPLE

A reliable northern seed strain

Collections at the northern edge of the eastern broadleaf forest

Establish maternal trees in Manitoba

10 2018‐02‐15

MANITOBA MAPLE

14,558 entries (4.8%)

Tough, native species

Well adapted to drought and alkaline soils

Many specimens show limited longevity

Cultivar: ‘Baron’

If it’s not male don’t plant it!

‘Autumn Splendor’ ‘Lavaburst’ OHIO BUCKEYE

431 entries (0.1%)

Moderate salt tolerance

Spring panicles

Excellent form Oak Street, Winnipeg Orange-red fall colour

Fruit drop may be an issue

Cultivar: ‘Autumn Splendor’

11 2018‐02‐15

MANCHURIAN ALDER

345 entries

Well adapted to drought and alkaline soils

‘Prairie Horizon’ Unique buds and foliage Vernon Road, Winnipeg

Sapsucker target

Cultivar: ‘Prairie Horizon’

PAPER BIRCH

1,488 entries (0.5%)

Native tree

Salt tolerant

‘Prairie Dream’ Moisture Bayview Drive, Winnipeg sensitive

Bronze birch borer in stressed planting sites

Cultivar: ‘Prairie Dream’ Stress-tolerant

12 2018‐02‐15

HACKBERRY

1,213 entries (0.4%)

Tolerance to alkaline soil and drought

Performs well in urban sites Morden, Manitoba Salt sensitive

Slow to establish

Storm damage

No northern

Polson Ave, Winnipeg ‘Delta’ strain

AMUR CORKTREE

25 entries

Aromatic compound leaves

Spongy bark

Extremely adaptable

Pest free

No northern cultivars

Limited nursery availability Queens Park Crescent, Winnipeg

13 2018‐02‐15

Portage la Prairie ‘Top Gun’ BUR OAK

17,125 entries (5.7%)

Drought tolerant

Long-lived species

Transplant shock – slow to establish - need for root modification

Sensitive to soil disturbance

Cultivar: ‘Top Gun’ Upright Trembley Street, Winnipeg

One summer’s growth - 2017 ADMIRATION HYBRID OAK

Interspecific hybrid

Budded on Bur oak for soil tolerance

Outstanding growth rate once established

Exfoliating bark

Few acorns

Propagators now on board

Original tree in Saskatoon

14 2018‐02‐15

‘Majestic Skies’ NORTHERN PIN OAK

21 entries

Toughest of the red oak group

Long-lived, drought tolerant

Red fall colour

Iron chlorosis; bud on Bur Oak

Cultivars: ‘Shooting Star’ ‘Majestic Skies’

‘Shooting Star’

AMERICAN LINDEN

All Tilia 29,289 entries (9.6%)

Excellent shade tree

Large leaves, fragrant flowers ‘True North’ Golden fall colour

Salt / drought sensitive

Avoid poorly drained sites

Cultivar: ‘True North’ Nicollet Avenue, Winnipeg

15 2018‐02‐15

LITTLE LEAF LINDEN

A Manitoba luxury versus zone 2

Medium-sized shade tree ‘Golden Cascade’

Dense canopy, ‘Greenspire’ small leaves stay green longer

More adapted to harsh urban sites than American

Cultivars: ‘Golden Cascade’ ‘Greenspire’

Grierson Avenue, Winnipeg

‘Dropmore’ HYBRID LINDENS

Additional diversity within the genus

‘Dropmore’ American x Little Leaf

‘Glenleven’ ‘Harvest Gold’ American x Little Leaf

‘Skinur’ American x Manchurian

‘Harvest Gold’ Mongolian x Little Leaf ‘Skinur’

16 2018‐02‐15

AMERICAN ELM

57,700 entries (19.2%)

Our best urban ‘Prairie Expedition’ shade tree

Crown form, drought tolerance

DED susceptibility

Overuse in the past

Cultivars: ‘Brandon’ ‘Prairie Expedition’

JAPANESE ELM

1,455 entries (0.5%)

DED-resistant

Nearly seedless form vs. American Useful as “utilitrees”

Can’t replace American Elm

Small stature, slower growth

Cultivar: ‘’ ‘Northern Empress’ ‘Discovery’

17 2018‐02‐15

HYBRID ELM

24 entries

DED-resistant

Fast growing

Poor crowns on some cultivars

Cultivar: ‘Triumph’ ‘Triumph’

Crown form “I am most impressed with the ascending limbs and favorable branch similar to attachment on the majority of trees I have seen. The structure is American reminiscent of the large old upright elms, with the tall broad canopy that enhances character and adds a sense of longevity to established Traces back to neighborhoods.” Manitoba Jim Barborinas, Urban Forest Nursery

WORTH A TRY

Successfully growing in and Fargo Bismarck, ND Excellent tolerance to alkaline soil, road salt

Take advantage of urban heat ‘Northern Acclaim’ Honeylocust island

Plant as larger trees

Cultivar / seed source is crucial Linacre Road, Winnipeg Kentucky Coffeetree – Portage la Prairie

18 2018‐02‐15

PARK TREES

Trees that have traits that preclude their use as boulevard trees

Low branching

Large fruit

Shallow rooting

Use these species in urban green spaces

WALNUT & BUTTERNUT

59 Butternut

40 Black Walnut

Unique: foliage, fruit, form

Attract wildlife

Transplant shock: tap-root

Drought intolerant

No cultivars Seed source is crucial! Gretna Bay, Winnipeg

19 2018‐02‐15

POPLAR & WILLOW

3,804 + 12,390 (5.4%)

Fast growing – Laurel Willow - Winnipeg over-aggressive

‘Sundancer’ Hybrid Poplar Shallow rooted

Cottonwood - Calgary Avoid aspens - BLD

Poplar cultivars: ‘Prairie Sky’ ‘Sundancer’

Willow cultivar: ‘Laurel’

CONIFERS

Low branches and winter shading limit usefulness as boulevard trees

Still have value Colorado Spruce in a zone where winter colour is hard to find Swiss Stone Pine Can be a part of the diversity solution

Siberian Larch

20 2018‐02‐15

SMALL TREES

FLOWERING TREES

WHY SMALL TREES?

Nothing else will fit!

Easy to prune

Colourful flowers/fruit

Space in yard for several choices

Part of the diversity solution

21 2018‐02‐15

AMUR MAPLE

1,986 entries (0.7%)

Grows as a shrub but can be tree- formed

Red fall colour ‘Ruby Slippers’

Cultivars: ‘Royal Crown’ Chlorosis resistant

‘Ruby Slippers’ Better crown form, but limited fall colour ‘Royal Crown’

TATARIAN MAPLE

79 entries – room for expansion

Slightly larger than Amur

More natural tree-form

Limited fall colour

Cultivar: ‘Hot Wings’ “Traffic-stopper” Outstanding red samaras - July 1 to September 15 ‘Hot Wings’

22 2018‐02‐15

HAWTHORN

290 entries (0.1%)

Older Morden hybrids that still ‘Snowbird’ ‘Toba’ have relevance

Excellent small trees

Double-white flowers

Sparse fruit production

Cultivars: ‘Snowbird’ ‘Toba’

FLOWERING CRABAPPLE

5,390 entries (1.8%)

‘Royalty’ Excellent ‘Selkirk’ small-statured ‘Thunderchild’ trees

Evolution in form - trend is towards upright

Conform to compact ‘Gladiator’ landscape Spire series spaces ‘Starlite’

23 2018‐02‐15

GLADIATOR ROSYBLOOM

New best- seller

Upright form

Glossy purple foliage

Bright pink flowers

Resistant to fireblight and scab

SPIRE ROSYBLOOM

Columnar habit

Disease-free

Potential as summer privacy screen

Cultivars: ‘Purple Spire’ ‘Emerald Spire’ ‘Purple Spire’ Sparse flowering Purple foliage in later summer

‘Emerald Spire’ More vigorous Abundant flowers

24 2018‐02‐15

STARLITE SIBERIAN

Siberian-type: White flowers

Tiny, retained fruit

Glossy, green foliage

Upright, pyramidal form

Better disease resistance than ‘Spring Snow’

‘Goldspur’ AMUR CHERRY

875 entries (0.3%)

Resistant to black knot

‘Klondike’ Golden exfoliating bark

Moderate salt tolerance

Issues with frost cracking

Cultivars: ‘Goldspur’

Wellington Crescent, Winnipeg ‘Klondike’

25 2018‐02‐15

Pyrus ussuriensis USSURIAN PEAR

100 entries

Tough tree that needs some tweaking

Soil tolerant

‘Navigator’ White blooms before leaves

Large, unwanted fruit

Cultivars: ‘Mountain Frost’ ‘Navigator’ ‘Mountain Frost’ Dobrinsky Drive, Winnipeg

EUROPEAN MTN ASH

Total Sorbus: 670 entries (0.2%)

Once widely planted

Concerns about disease and bird damage

‘Rossica’ Cultivar: ‘Rossica’

Upright crown

Improved fireblight resistance Uxbridge Road, Winnipeg

26 2018‐02‐15

SHOWY MTN ASH

Total Sorbus: 670 entries (0.2%)

Under-rated, native species

Rounded crown

4 season value

Fire blight resistant

Not affected by sapsuckers

JAPANESE TREE LILAC

2,036 entries (0.7%)

Still one of the best small trees

Salt tolerant

Verticillium ‘Ivory Pillar’ issue

Cultivars: ‘Ivory Silk’ was considered best

‘Ivory Pillar’ Upright form Clean foliage Verticillium R Polson Avenue, Winnipeg

27 2018‐02‐15

STEPS FOR A MORE SUSTAINABLE URBAN FOREST

In-plant diversity at every opportunity Keep planting and protecting

Give precedence to residential streets No more monocultures – its time to mix it u

QUESTIONS?

Download a copy of this presentation at: www.jeffriesnurseries.com/newjnl.htm

28 2018‐02‐15

THE VALUE OF AN URBAN FOREST

Increasingly recognized

“priceless”

29