Street Trees 8 - Thomas deHaas

This week we look at what some very durable choices of Elms for street trees.

American Elm cultivars are still available and are up to 99% resistant to Dutch Elm Disease. These cultivars included Ulmus americana ‘Jefferson’ Jefferson Elm,Ulmus americana ‘JFS Prince II’ ™, Colonial Spirit ™ Elm, Ulmus americana ‘New Harmony’, New Harmony American Elm,Ulmus americana ‘Princeton’, Princeton Elm,Ulmus americana ‘Valley Forge’, Valley Forge Elm. All these varieties are sold and available from nurseries.

On rare occasions American Elm cultivars can contract Dutch Elm Disease. Dutch elm disease (DED) is one of the most destructive urban forest diseases. This disease affects native American elm species, such as American (Ulmus americana), slippery (red) (U. rubra), winged (U. alata), rock (U. thomasii), September (U. serotina), and cedar (U. crassifolia) elms. The Asiatic elms, such as Siberian (U. pumila), Japanese (U. japonica), or lacebark (U. parvifolia) elms, are much less susceptible to DED, and the disease is not considered an issue for these species.

One other caution is Elm Yellows:

There are several very good Elm hybrids. One US National Arboretum introduction is Ulmus x ‘Frontier’, Frontier Elm is an excellent choice for street tree. This tree is a fast grower, resistant to DED, and has a great fall color. Another great selection is Ulmus parvifolia 'Emer II'™, Allee Elm.This is another tree that tolerates urban condition. Ulmus propinqua ‘JFS-Bieberich’™, Emerald Sunshine Elm tolerates heat and drought and is an adaptable tree for larger spaces. Ulmus parviflora, Lacebark Elm is a fast grower, insect and disease resistant, and has exfoliating bark. Ulmus pumila, Siberian Elm should not be used as it is listed as invasive.

Zelkova serrata, Zelkova has been used as an urban tree.Zelkova serrata ‘Schmidtlow’™, Wireless A Zelkova has a great form for a street tree. There are other Zelkova serrata cultivars to consider. Zelkova serrata ‘Green Mansions’, Green Mansions Zelkova, Zelkova serrata ‘Green Vase’Green Vase Zelkova, Zelkova serrata ‘Mussahino, Mussahino ColumnarZelkova grown tightly columnar and makes a narrow street tree.

Consider adding Elms and Zelkova to add diversity and beauty to your street plantings and park settings.