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Problem
Plants and Alternatives |
By Jim Klett,
professor, Colorado State University Department of Horticulture and Landscape Architecture
Plants are a little like human beings. No
one of them is perfect.
Certain plants, however, are more resistant to
diseases and insects. Below is a list of trees, shrubs and vines that cause problems,
along with plants that can be substituted for them.
Trees
Problem plants |
Possible substitutions |
Siouxland
Cottonwood (Populus deltoides `Siouxland') |
White
Poplar (Populus alba) |
Lombardy
Black poplar (Populus nigra `Italica') |
Upright
European Aspen (Populus tremula `Erecta') |
Bolleana
White Poplar (Populus alba `Pyramidalis') |
Tower
Poplar (Populus `Tower') |
Downy
Hawthorn (Crataegus mollis) |
|
American
elm (Ulmus americana) |
- Chinese Elm
(hardiness ?) (Ulmus parvifilia)
Various new elm hybrids,
such Siberian elm as `Accolade Elm,' `Cathedral Elm,' `Vanguard
Elm' and new U.S. National Arboretum `Valley Forge' and `Homestead.'
(Ulmus pumila)
|
`Plena'
Bechtel Crabapple (Malus ionensis) |
Centurion Crabapple
(Malus `Centurion')
David Crabapple
(Malus `David')
Coralburst Crabapple
(Malus `Coralburst')
|
Additional Shade Trees
| Newer or Not Planted as Much |
Standard or Older |
Black Ash (Fraxinus nigra)
Growth habit - small to
medium-size tree Extremely hardy
Cultivar `Fallgold' is a seedless
clone with disease free foliage, good gold fall color
|
Green Ash (Fraxinus pennsylvanica)
Growth habit - naturally more
irregular
Seedlings can have fruit if female
plant
Plant generally hardy and
adaptable to our soils
|
Ussurian Pear Pyrus ussuriensis
- Growth habit - small tree or large multistem shrub
- Hardiest of all pears from N.E. Asia, more
resistant to fireblight
- White flowers early in spring
- Leaves are glossy green in summer and reddish
purple in fall.
|
`Bradford Pear' Pyrus calleryana
- Growth habit - conical
- Subject to breakage from early or late snows and
ice storms
- Hardiness more questionable for area Good flowers
and fall color
|
Tatarian Maple Acer tatarium
- Growth habit: Multistem shrub or single stem
smaller tree
- Good greenish-white flowers followed by red samara
fruit in July-August
- Appears more adaptable to our clay soil with
higher pHs
|
Amur Maple Acer ginnala
- Growth habit: similar to Tatarian Maple
- Often shows some chlorosis in higher pH soils
- Fruits generally do not turn red in mid-summer
- Has superior fall color
|
Amur Chokecherry Prunus maackii
- Growth habit: small, dense branching tree or
larger multistem shrub
- Good white flowers followed by green
|
Newport Plum Prunus cerasifera
'Newport'
- Growth habit: similar ultimate size
- Understock often lacks hardiness and has been
observed to have more winterkill
- Plant has purple foliage throughout the season,
whereas Amur Chokecherry does not
- Excellent bark characteristics
- Does not appear to sucker much
- Purple fruit
- Appears very cold hardy
|
| Newer
or Not Planted as Much |
Standard
or Older |
'Emerald Mound'
Lonicera xylosteum Emerald Mound Honeysuckle
- Growth habit - low growing mounded honeysuckle
- Foliage - rich, blue-green
- Gets about 3 feet tall and 4 to 6 feet wide
- No aphid damage
Miniglobe' Lonicera
xylosteum - Miniglobe Honeysuckle
- 1981 introduction from Morden Research Station
- Hardier than `Emerald Mound'
- More compact with dense green foliage
- No aphid damage
|
Lonicera
tatatica - Tatarian HoneysuckleGrowth habit - upright arching with dense
twiggy mass
Flowers - pink with red fruit
Leafs out early, often hit by late frosts
Very susceptible to honeysuckle aphid
|
Meyer Lilac
Syringa meyerii `Palibin'
- Growth habit - dwarfer, denser rounded habit, 4 to
5 inches high and 5 to 7 inches wide
- Reddish purple flower buds that open to whitish
pink
- Blooms early in its age
- Leaves smaller, don't show mildew
|
Common Lilac
Syringa vulgaris
- Growth habit - upright leggy shrub which is often
void of lower branches after time
- Lilac extremely fragrant flowers
- Often gets mildew on leaves and borers
Chinese Lilac Syringa
x chinensis
- Growth habit - broad spreading, round topped with
arching branches
- Purple-lilac fragrant flowers in loose panicle
inflorescence
- Can get mildew and borers
- Can get open, not pleasant looking with age
|
`Compactum'
Viburnum opulus Compact European Cranberrybush Viburnum
- Growth habit - about 1/2 size of V. opulus,
dwarfer and denser
- Excellent in flower and fruit
- Good plant for smaller spaces
- Not as affected by aphids and other pests
|
European
Cranberrybush Viburnum Viburnum opulus
- Growth habit - upright, spreading, multi- stemmed
shrubs with branches arching to ground
- Flowers - white with pinwheel effect in May
getting 2 to 3 inches in width
- Fruit - Red berry-like drupe which can persist
into winter
- Often infested with aphids and borers
|
`Compactum' Viburnum
trilobum Compact American Cranberrybush
- Growth habit - more compact, upright- spreading
with more slender stems
- About 1/2 size of V. trilobum
- Excellent fall color (red/purple)
- Good in flower and fruit
- Not as affected by aphids and other pests
|
`Roseum'
Viburnum opulus European Snowball
- Growth habit - form with sterile flowers which are
very showy in spring
- Aphids really seem to infest this clone
|
Vines
| Newer
or Not Planted as Much |
Standard
or Older |
'Emerald Mound'
Lonicera xylosteum Emerald Mound Honeysuckle
- Growth habit - low growing mounded honeysuckle
- Foliage - rich, blue-green
- Gets about 3 feet tall and 4 to 6 feet wide
- No aphid damage
Miniglobe' Lonicera
xylosteum - Miniglobe Honeysuckle1981 introduction from Morden Research Station
Hardier than `Emerald Mound'
More compact with dense green foliage
No aphid damage
|
Lonicera
tatatica - Tatarian HoneysuckleGrowth habit - upright arching with dense
twiggy mass
Flowers - pink with red fruit
Leafs out early, often hit by late frosts
Very susceptible to honeysuckle aphid
|
Japanese Creeper or Boston Ivy Parthenocissus tricuspidata
- Growth habit - vigorous but often has shorter
tendrils and neater appearance on walls
- Leaves often simple and darker glossy green with
red-purple fall color
- Does not seem to get mildew as much
- Neater, finer appearance overall
|
Virginia
Creeper Parthenocissus quinquefolia
- Growth habit - very vigorous vine with tendrils
that have 5 to 8 branches with adhesive-like tips
- Leaves, 3 to 5 leaflets, dark green, courser
texture and turn red in fall
- Often gets downy mildew and leaf spot on leaves
- More course overall texture
|
Photograph of Russian Hawthorne Tree courtesy of Judy Sedbrook.
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