russian hawthorn (23227 bytes)

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)

  • Thornless Cockspur Hawthorn (Crataegus crusgalti inermis)

  • Washington Hawthorne (Crataegus phaenophyrum)

  • Russian Hawthorn (Crataegus ambigua)

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)

  • Brandywine Crabapple (Malus `Hopa', Malus `Brandywine')

  • 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

Shrubs

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 Honeysuckle
  • Growth 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 Honeysuckle

  • 1981 introduction from Morden Research Station
  • Hardier than `Emerald Mound'
  • More compact with dense green foliage
  • No aphid damage
Lonicera tatatica - Tatarian Honeysuckle
  • Growth 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.

Back to Trees and Shrubs

Back to Vines

Back to Home

 

 

Ask a Colorado Master Gardener | Calendar | Children | Container GardeningCSU Fact Sheets
Credits | Diseases | FAQ | Flowers | Fruits | Gardening | GlossaryHouseplants | Insects & Pests
Lawn & Grasses | Links | New to Colorado | PHC/IPM | Soil | Shrubs | Trees
Vegetables | Water Gardening | Weeds | What's New | Who We Are | Xeriscape

Search

line4.gif (1411 bytes)

Contact Us | Disclaimer | Equal Opportunity

CSU/Denver County  Extension Master Gardener 2010
888 E. Iliff Avenue,  Denver, CO 80210
(720) 913-5278

E-Mail: denvermg@colostate.edu  

Date last revised: 01/05/2010