About Elm Shade Trees
The majestic size and beautiful arching form of the prized American Elm and the English Elm may have been forever lost to the devastating Dutch Elm Disease.
Dutch Elm disease has devastated elms, affecting all species native to North America and Europe. The greatest decline came in the 1960’s, but disease resistant cultivars have encouraged reestablishment of the elms since about 1990. Resistant varieties cannot match the size and form of the American and English Elm, hardest hit by the disease. Elm cultivars that are resistant to Dutch Elm disease have increased to about 300, and the Asiatic species have proven to be resistant. However the Asian species do not have the classic vase shape that makes the American elm so lovely lining the streets of North America, creating beautiful shade canopies. The Asian species also does not seem to be as hardy overall as the American elms. Specific American elms that have survived the disease have been cloned or crossed with resistant species to develop new hybrids.
There are roughly 30 to 40 elm species, the majority are from China, with about 8 species from North America and fewer from Europe. The Chinese Elm ‘parvifolia’ is commonly used for bonsai.
Elms are primarily deciduous, however some are semi-deciduous, meaning leaves drop only when new leaves are pushing them off. The leaves are simple serrated and are usually not symmetrical. Flowers are both male and female, but have no petals. The fruit (seeds) are small round samaras that are dispersed by the wind. The Elm species are all quite tolerant of a wide range of soil types and pH levels and demand good drainage. Except the European White Elm, which prefers wet soil conditions.
Elm wood has interlocking grain, making it resistant to splitting. The strong wood of the Elm makes it resistant to wind damage, one of the many reasons it has been such a desirable street and landscape tree across North America. However the roots are shallow and cause buckling and heaving of nearby sidewalks. The large elm trees provide excellent shade and protection for structures. In addition to being wind resistant, elm are hardy, suited to cold climates, and tolerant of adverse conditions and pollution. The elms are long lived and grow at a moderate rate. The seeds attract birds and wildlife, but can be produced in abundance, considered a nuisance by some.