Growth Characteristics
American elm is one of our most urban tolerant native trees. American elms can reach heights of 75-100 feet along streets, but their vase-shaped habit and natural pruning of lower branches will allow them to grow over powerlines with substantially less pruning than other trees (such as maples). Elms tolerate heavy stresses such as soil compaction, salt, and poor drainage. Fall color is good and fallen leaves are light and easy to collect and decompose relatively rapidly into compost.
"Dutch Elm Disease" (DED) is the the major drawback to planting of American Elms. However, disease-resistat varieties are now increasingly available in the trade. The elm is equally suseptible to Dutch Elm Disease, and Elm Yellows (or phloem necrosis) although the latter is much less common. Ironically, this tree was once overplanted to such an extent that it became a symbol for improvement of biodiversity in our cities, but now planting of elms can actually improve biodiversity in the urban forest canopy. Many elms continue to survive in urban settings today (see photo below)
Disease Resistance
Dutch Elm Disease tolerant cultivars include 'Princeton', 'Valley Forge' and 'New Harmony'. 'Valley Forge' and 'New Harmony' American elms were introduced in the late 1990s from the National Arboretum. Of the disease resistant cultivars, 'Princeton' is generally considered to have the best form and growth rate, 'New Harmony' has the highest disease resistance, and while 'Valley Forge' also has good disease resistance, its habit is somewhat 'shrubbier' than the other two. Take a look at the pictures below of recent plantings of Princeton elms in Cincinnati. The Princeton American elm was introduced by Princeton Nursery around 1920 about ten years before DED was introduced. Its disease tolerance remained unknown until the 1990s, as everyone forgot about the reasons for growing American elm and concentrated on remembering why you should not grow the plant. It is important to note that elms tolerant of Dutch Elm disease have not been proven to be tolerant of elm yellows. Cultural sanitation practices, and systemic fungicides such as Alamo ® have been shown to be effective. Let us use the loss of this urban tolerant tree as a reminder of why we need diversity, and remember to plant a tree for what it can do.
The number of nurseries producing DED-resistant American elms is increasing every year. In internet search for "Disease-Resistant American Elms" will now easily turn-up multiple sources
Disease Resistant Elms are also available from:
EARTHSCAPES Inc.
10403 State Rt. 48
Loveland, Ohio 45140
Phone: 513-683-0844
