2017‐03‐15 1 PHILIP RONALD, PH.D. BEST TREES AND SHRUBS FOR HARDINESS ZONES 4 AND NORTHWARD MINNESOTA SHADE TREE SHORT COURSE MARCH 2017 INTRODUCTION What’s “best”? Stick with the tried & true? or Sift through the masses of new cvs? Change is necessary Improved genetics New pests Smaller, lower maintenance yards But remember: marketing does not always lead to a great plant 260 TREE CULTIVARS AT 4 SITES OVER 6 YEARS 200 SHRUB CULTIVARS PLANTED OVER 4 YEARS A UNIQUE STATE Minnesota: converging eco-zones Terminus of the eastern broadleaf forest Native species 50 trees 200 shrubs The value of proper provenance SOIL pH Severely restricts some plants Impact on micro-nutrient availability Determined by >parent material >summer moisture MN is divided: 1/3 alkaline 6.5 - 8 2/3 acidic 5.5 – 6.5 Thief River Falls, MN WINTER TEMPERATURE What’s up with the weather? Global warming? Revised zone map Remember the polar vortex of 2014 Cold is still a limiting factor CELEBRATE WINTER No deciduous foliage - 5-6 months of the year Consider a tree/shrub’s winter value: form, bark, fruit, buds Value of evergreens
Transcript
2017‐03‐15
1
PHILIP RONALD, PH.D.
BEST TREES AND SHRUBS FOR
HARDINESS ZONES 4 AND
NORTHWARD
MINNESOTA SHADE TREE SHORT COURSE
MARCH 2017
INTRODUCTION
What’s “best”?
Stick with the tr ied & true?
or
Sif t through the masses of new
cvs?
Change is necessary
I m pr oved g e n et ic s
New pe s ts
S m a l l e r, l ow e r m a i n tenanc e ya r ds
But remember: market ing does
not a lways lead to a great p lant
2 6 0 T R E E C U L T I V A R S A T 4 S I T E S O V E R 6 Y E A R S 2 0 0 S H R U B C U L T I V A R S P L A N T E D O V E R 4 Y E A R S
A UNIQUE STATE
Minnesota: converging eco-zones
Terminus of the eastern broadleaf
forest
Native species
50 trees
200 shrubs
The value of proper
provenance
SOIL pH
Severely restr icts some
plants
Impact on micro-nutrient
availabil ity
Determined by >parent material>summer moisture
MN is divided:1/3 a lkal ine
6.5 - 82/3 acidic5.5 – 6.5
Thief River Falls, MN
WINTER TEMPERATURE
What’s up with the
weather?
Global warming?
Revised zone map
Remember the polar
vortex of 2014
Cold is sti l l a l imiting factor
CELEBRATE
WINTER
No deciduous foliage - 5-6
months of the year
Consider a tree/shrub’s winter value: form, bark, fruit, buds
Value of evergreens
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TREES
UNIQUE TREES
Needed for diversity
John Ball:
Beware of genera found
on all 3 continents
Ash
Elm
Linden
Oak
Maple
Pine
Poplar
Spruce
Dr. Frank Santamour proposed a 10-20-30 formula10% within a species, 20% within a genus, 30% within a family
Dr. John Ball proposed a 5% formula for diversityNo more than 5% of a community’s trees be in one genus
Green Ash monoculture
DNR TREE SURVEY
2010 - rapid assessments
for every community
boulevard, ROW and front-yard
trees
3 genera = more than 50% of all
urban trees
VulnerableTrees are a long-term investment
A lack of diversity = catastrophe
CHALLENGES
Our trees face many abiotic
challenges
BUT
The greatest threats are
l iving
General vs specific pests
Invasive alien species
URBAN SOILS
Top-soil of ten stripped
Compaction of subsoil
Poor drainage
Minimal water infiltration
Little organic matter
Downtown Winnipeg, MB
Same site – 1 year later
OTHER CONCERNS
Desire reduced maintenance
Preserve ornamental
features
ELIMINATE:
Poor crowns
Aggressiveness
Root sprouts
Weediness
Fruit drop
Ussurian Pear
Green Ash volunteersCathedral Elm
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MEDIUM & LARGE TREES
Overused in many areas
Needed in alkaline areas
western MN
‘Prairie Rouge’&
‘Regal Celebration’
Alkali-tolerant
early red fall colour
Zone 2Fall colour on September 29, 2016
Fall colour on September 22, 2014
‘Prairie Rouge’ - red
MAPLE
‘Regal Celebration’
BUCKEYE
‘Autumn Splendor’
H: 35’ W: 25’
University of Minnesota
introduction
Spring panicles
Red fall colour
Sparse fruiting
MANCHURIAN ALDER
‘Prairie Horizon’
H: 35’ W: 20’
NDSU introduction
Zone 2 hardy
Drought tolerant
Unique buds and foliage
BUT a magnet for sapsuckers
PAPER BIRCH
‘Prairie Dream’
H: 50’ W: 35’
Selected in Killdeer Mtns
of N.D.
Bark turns white at a very
early age
Resistance to moisture
stress that protects vs.
BBB
ASIAN WHITE BIRCH
‘Parkland Pillar’
H: 30’ W: 9’
Columnar selection of
‘Dakota Pinnacle’
Susceptible to BBB
Apply mulch to ensure cool
root zone
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HACKBERRY
Famous for trunk failures
Excellent tolerance to alkaline soil
and urban stresses
Seed source is important
‘Prairie Sentinel’
H: 45’ W: 12’Kansas source
Almost works in zone 3
Winnipeg, MB
‘Prairie Sentinel’
GINKGO
An underused genus
Indicator plant for zone 4
High tolerance to alkaline
soil and urban stresses
‘Autumn Gold’H: 45’ W: 35’
Pyramidal
Seedless
Ginkgo after 1 winter in zone 3
Ginkgo on Watson Ave., St. Paul, MN.
HONEYLOCUST
Excellent tolerance to alkaline soil
and urban stresses
Choose your cultivar
carefully
Juvenile cold hardiness
varies
‘Northern Acclaim’
H: 45’ W: 35’Zone 3b
‘Street Keeper’ in zone 3
‘Northern Acclaim’
KENTUCKY COFFEE TREE
Excellent tolerance to alkaline soi l ,
urban stresses
Seed source is crucial
Use maternal trees in
nor thern great plains
Male cult ivars for zone 4:‘Espresso’H: 40’ W: 35’
‘True Nor th’H: 50’ W: 35’
Bismarck, N.D.
IRONWOOD
Underused species
Pyramidal tree when young
Dark green fol iage turns yel low in fal l
Tolerates alkaline soi ls
and shade
‘Autumn Treasure’
H: 40’ W: 20’JFS introZone 4
AMUR CORKTREE
Aromatic compound
leaves
Spongy bark
Pest free
Male cultivars for zone 4
‘Eye Stopper’H: 40’ W: 35’
‘His Majesty’H: 40’ W: 35’
‘Eye Stopper’
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NORTHERN PIN OAK
Toughest of the red oak
group
Red fall colour
Susceptible to oak wilt
‘Majestic Skies’
H: 60’ W: 45’Zone 4
‘Shooting Star’H: 50’ W: 30’
Zone 3‘Shooting Star’
‘Majestic Skies’
HYBRID OAK
‘Admiration’bicolor x alba
H: 40’ W: 30’
Exfol iating bark
Zone 2
‘Prairie Stature’
robur x alba
H: 40’ W: 30’
Red fal l color
Zone 3b
Fargo, N.D.Saskatoon, SK
COLUMNAR HYBRID OAK
Only a dream in zone 3!
But possible in zone 4
‘Kindred Spirit’
&
‘Regal Prince’
(robur x bicolor)
‘Crimson Spire’
(robur x alba)
‘Regal Prince’ ‘Kindred Spirit’
‘Crimson Spire’
MOUNTAIN ASH
Under-rated genus
4 season value
European
‘Rossica’
H: 30’ W: 12’
Upright crown
Showy
H: 25’ W: 20’
Native
Round crown
‘Rossica’
Showy
MONGOLIAN LINDEN
‘Harvest Gold’Mongolian x Lit t le Leaf
H: 40’ W: 25’
Zone 3
Exfoliating bark
Golden fall colour
Resistant to
> Sunscald
> Japanese beetle
Mongolian Linden
‘Harvest Gold’
DED-RESISTANT
ELMS
‘Triumph’
Hybrid Elm
H: 60-75’
W: 70-90’
Very fast growing
Vase- l ike canopy
‘St Croix’ American Elm
H: 60-75’
W: 70-90’
Better branching vs Prair ie Exp?
‘Triumph’
‘Prairie Expedition’
‘St. Croix’
Japanese elm
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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
TATARIAN MAPLE
‘Hot Wings’
H: 23’ W: 20’
“Traf f ic -stopper”
Outstanding red samaras - J u l y 1
to Se pte m ber 15
‘Ruby Sl ippers’
H: 20’ W: 20’
Listed as Amur Maple
Better tree form vs ‘Hot Wings’ ,
but inferior samara colour
‘Ruby Slippers’
‘Hot Wings’
‘Hot Wings’
HYBRID
CARAGANA
‘Green Spires’ H: 12’ W: 8’
Hybrid(a r b o r e s c e n s x f r u t e x )
Clean foliage
Yellow flowers
Seedless
Drought and salt tolerant
Highways?
Original plant in shelterbelt
Flowers but no fruit
FLOWERING CRABAPPLE
Foliar disease resistance is
crucial
SCAB RATINGS:
0%
‘Starlite’
10-20%
‘Gladiator’
Over 50%
‘Spring Snow’ ‘Pink Spires’
‘Thunderchild’‘Thunderchild’ – August 29‘Starlite’
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’
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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’
FLOWERING CRABAPPLE
‘Gladiator’ Rosybloom
H: 20’ W: 9’
Upright form
Glossy purple foliage
Bright pink flowers
Resistant to fireblight and
scab
FLOWERING CRABAPPLE
‘Starlite’ Siberian-type
H: 25’ W: 15’
White f lowers
Tiny fruit
Green foliage
Upright form
Outstanding disease
resistance
SPIRE ROSYBLOOM
‘Emerald Spire’ &
‘Purple Spire’
H: 15’ W: 6-8’
Columnar
Slow growing
Disease-free
Potential as summer
privacy screen
‘Emerald Spire’‘Purple Spire’
AMUR
MAACKIA
Curly and exfoliating
bark
White flowers in spikes in July -August
In zone 3, we see chlorosis
and winter kil l
In zone 4, try ‘Summertime’
15’ x 12’
‘Summer Frost’ in MB ‘MaacNificent’ in MB
Emerging spring foliage
AMUR CHERRY
GoldspurH: 15’ W: 9’
A new look for the species
Tufted, peach-like foliage
Golden exfoliating
bark
Produces a dense crown and calipers
well
Original tree
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TREE LILAC
Overused, but stil l one of the
best small trees
‘Ivory Silk’ was
considered best cv
‘Ivory Pil lar’
H: 23’ W: 16’Upright form
Clean foliage
Large panicles‘Ivory Pillar’
ARBORVITAE
‘Skybound’H: 18’ W: 4’
Year-round privacy screen
Developed in Manitoba
zone 2
Resistant to winter
browning
Dense whorled fol iage also
resists splaying
‘Technito’
‘Skybound’
SHRUBS
BARBERRY
Compact & colour ful
Heat tolerant
Drought tolerant
Zone 3
‘Concorde’H: 2 ’ W: 2 -3 ’
T idy ba l l shape
Deep purp le summer fo l iage
Red fa l l co lour
Zone 4
‘Admiration’
Proven Winners
Sunjoy series (9)‘Concorde’
‘Emerald Carousel’
Bailey - Oregon
Sunjoy series
November 9/16
September 29/16
‘Concorde’
‘Admiration’
‘Admiration’
DOGWOOD
Outstanding winter stems -red and yellow
Shade tolerant
New compact cultivars
That can’t be a dogwood!
H: 3-4’ W: 3-4’
‘Arctic Sun’
‘L itt le Rebel ’
‘Pucker Up’
‘Red Gnome’
‘Red Gnome’
‘Little Rebel’
‘Pucker Up’
‘Arctic Sun’
DIERVILLA
Native plant
Sun or shade
Drought tolerant
H: 3-4’ W: 3-4’
F irst Edit ions
‘Cool Splash’
Variegated fol iage
Proven Winners
‘Kodiak Black’
‘Kodiak Orange’
‘Kodiak Red’‘Cool Splash’
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FORSY THIA
Outstanding spring f loral
display
Flower bud hardiness proven
MeadowlarkH: 8 -10’ W: 6 -8 ’
Nor thern GoldH: 6 -8 ’ W: 5 -7 ’
Dwar f cult ivars from Europe
Gold TideH: 2 -3 ’ W: 3 -4 ’
Show Of fH: 2 -3 ’ W: 2 -3 ’
‘Show Off’ ‘Gold Tide’
November 9, 2016 November 9, 2016
Differing flower bud hardiness across cultivars (Photo credit: U of Minnesota)
NINEBARKBolting
The most significant
shrub genus in zone 3
Vigorous and tolerant
Issue of bolt ing
True dwarfs available
Tree-forms showcase bark
but have the problem of
basal sprouts Little Devil
AMBER JUBILEE
NINEBARK
Diabolo x Dart’s Gold
H: 5-6’ W: 4’
Foliage colour breakthrough
Spring foliage:
Yellow-orange
Fall foliage:
Red, purple
Spring foliage
Fall foliage
NINEBARK SIZING
Smaller stature
Finer texture
LARGE (6-8’):‘Diabolo’
‘Center Glow’‘Coppertina’
MEDIUM (4-6’) :‘Summer Wine’ – mi ldew res is tant
DWARF (3-4’):‘Little Devil ’‘Tiny Wine’
Diabolo®
Center Glow®
Coppertina®
Summer Wine®
Little Devil®
Tiny Wine®
NINEBARK SIZING
Mature size without
intervention
LARGE (6-8’):
‘Darts Gold’
‘Lemon Candy’
MEDIUM (4-6’) :
‘Tiny Wine Gold’
DWARF (3-4’):
‘Festivus Gold’
Diabolo® Summer Wine®
‘Dart’s Gold’
Dwarf version of Dart’s Gold, H: 3’ W: 4’
‘Lemon Candy’
‘Festivus Gold’
HYDRANGEAS
Very flor iferous
Long-lasting flowers (sepals)
Since 2000, over 90
hydrangeas patented
Abundant introductions,
but l imited testing
Remember, new is not always
improved!
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SMOOTH HYDRANGEA
‘Annabelle’, the standard
for comparison
Flowers occur in dome-shaped
inflorescences (corymbs)
Dirr: “sti ll the best white mophead”
SMOOTH HYDRANGEA
Incrediballseries
‘ Incredibal l ’
‘ Incredibal l Blush’
Invincibelleseries
‘ IV Limetta’
‘ IV Mini Mauvette’
‘ IV Ruby’
‘ IV Spir i t I I ’(3-4’ )
‘ IV Wee White’(1-2’ )
‘IV Wee White’
‘IV Spirit II’
‘IV Limetta’
‘Incrediball Blush’
‘Invincibelle Ruby’
PANICLE HYDRANGEA
20+ cultivars in the
marketplace
Red flowered cultivar =
“holy grail”‘Diamond Rouge’
H: 4-5’ W: 3-4’
‘F i re Light’H: 5-6’ W: 4-5’
Tree-forms sell ing well;
concerns about
hardiness in zone 3
FE ‘Diamond Rouge’
PW ‘Fire Light’
‘Limelight’ - tree
PANICLE HYDRANGEA BLOOM TIME
Bloom time is more important
the fur ther nor th you go!
Want to maximize
flower duration in summer
At least mix and match cvsfor al l -summer
blooming
July 31, 2008
September 29, 2008
(L) ‘Quick Fire’ – ‘Limelight’ (R)DATE OF FULL
BLOOM IN MANITOBA:
Very early bloomers (July 20):
‘Quick Fire’‘Lil’ Quick Fire’
‘Bobo’
Early bloomers (July 30):
‘Little Lamb’‘Pinky Winky’
‘Vanilla Strawberry’
Mid-season bloom(August 10)‘Limelight’
‘Little Lime’‘Fire Light’
Late-season bloom(August 20):‘Mega Mindy’
PANICLE HYDRANGEA
Little Lime
LARGE (H: 6 -8 ’ ) :
‘Great Star ’
‘L imel ight ’
‘P i l low Ta lk ’
‘P inky Winky ’
‘Qu ick F i re ’
‘Vani l la St rawberr y ’
‘Z inf in Dol l ’
MEDIUM (H: 4 -6 ’ ) :
‘D iamond Rouge’
‘L i t t le Lamb’
‘F i re L ight ’
‘Mega Mindy ’
‘St rawberr y Sundae’
‘T ick led Pink’
DWARF (H: 3 -4 ’ ) :
‘L i t t le Quick F i re ’
‘Bobo’
‘L i t t le L ime’
‘Bobo’
‘Little Quick Fire’ ‘Little Lime’
POTENTILLA
‘Lemon Meringue’
‘Citrus Tart’
‘Crème Brulee’
Tough plant
Drought tolerant
Prolific bloomer from spring to fall
FE Cu l t i vars
‘C i t rus Tar t ’
‘C rème Bru lee’
‘Lemon Mer ingue ’
Jef f r ies Cu l t ivar
‘Mandar in Tango’
‘Mandarin Tango’
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SUMAC
‘Tiger Eyes’ Cutleaf
StaghornH: 6’ W: 6’
A “must have”
Soil tolerant
Limited suckering
Summer: contrast with
purple accents
Fall colour: orange, red
SPIREA
Compact, ful l sun plant
Impressed with:‘Pink Parasols’H: 2-3’ W: 3-4’Wakes up early
Fluf fy pink f lowers
Newer cult ivars:FIRST EDITIONS
‘Sundrop’‘Pink Sparkler ’
‘Superstar’
PROVEN WINNERS
‘Double Play x 8’
‘Pink Parasols’ in zone 3
June 15/16 - 3 years post-plant
‘Pink Sparkler’ ‘Double Play Red’
HYBRID
LILAC
‘Little Lady’
‘Miss Kim’
Compact habit vs French,
Preston
‘Litt le Lady’(Dwar f Korean x
Miss K im)Half the size of
‘Miss Kim’
‘Scent & Sensibi l ity’
H: 2-3’ W: 4-5’
Compact and re-blooming
‘Bloomerang’ Series
H: 4-6’ W: 4-6’‘Bloomerang Dark Purple’‘Scent & Sensibility’
