Q. Are disease-resistant varieties of the American elm available?
Most of the elm trees growing in the U.S. (and other countries) have been eliminated by an infection from a fungus (Ophiostoma novo-ulmi), which causes the devastating Dutch elm disease. Considerable effort has been expended to produce disease-resistant varieties and cultivars of this beautiful tree. Although none of the new varieties are completely resistant to the disease, a number can now be recommended for the home gardener.
- 'Valley Forge' -- a cultivar isolated by the U.S. National Arboretum tree genetics program. This seems to be the most resistant cultivar isolated so far. It has the typical vase shape characteristic of American elms.
- 'New Harmony' -- another cultivar developed by the U.S. National Arboretum. It is probably not quite as disease resistant as 'Valley Forge.'
- 'Princeton' --an older cultivar with moderate disease resistance.
Some elm species other than the American elm (Ulmus americana) and the English elm (U. procera) are naturally resistant to Dutch elm disease. These include the Chinese elm (U. parvifolia), which has been widely planted as a substitute for the American and English species. It does not, however, have the beautiful vase form characteristic of the Western species.
A number of hybrids have been developed using different species of elms to produce cultivars that have both disease resistance and good form as well as being easy to grow. May of them are commercially available. See Iowa State cooperative extension's Dutch elm disease pages for a general discussion of Dutch elm disease and resistant cultivars.
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- Courtesy of NYBG Plant Information Service