Siberian Elm - Ulmus pumila

Siberian Elm - Ulmus pumila [2]
Elm Family: Ulmaceae.
Classified as an invasive in North America, the Siberian elm is a medium sized tree reaching up to 70 feet tall.
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Siberian Elm - Ulmus pumila, Morton Arboretum acc. 325-70*4 is 37-years-old.

The crown is open and rounded with slender, spreading branches. The leaves are small (< 2 in.) alternate, simple, singly-serrate, and dark-green in color. The bark is light-gray with irregular furrows. Siberian elm invades pastures, roadsides, and prairies throughout the Midwest and Great Plains regions of the United States. The trees are very drought and cold resistant allowing it to grow in areas where other trees cannot. The abundant, wind-dispersed seeds allow this plant to spread rapidly, forming dense thickets that close open areas displacing native vegetation and reducing forage for wild animals and livestock. Siberian elm is native to northern Asia and was first introduced into America in the 1860s. It has been planted throughout the Midwest and Great Plains for windbreaks and lumber.

In North America, Ulmus pumila is an invasive species, spreading from Utah east to Kansas and north to Ontario. It is found in abundance along railroads and in abandoned lots and on disturbed ground. The gravel along railroad beds provides ideal conditions for its growth: well-drained, nutrient poor soil, and high light conditions, and these beds provide corridors which facilitate its spread. Owing to its high sunlight requirements, it seldom invades mature forests, and is primarily a problem in cities and open areas.

These are the leaves of the Siberian Elm - Ulmus pumila

I have no idea why these leave look so.. diseased. Almost all the elms looked terrible this July day in 2007. This was at the height of the 17-year cicada emergence, but I doubt that had anything to do with it.

Leaf: alternate, simple, elliptical to ovate, 1 to 2 1/2 inches long, singly serrated margin, nearly an equilateral base, dark green and smooth above, paler and smooth below. Flower: Monoecious; small, pale green clusters occurring in early spring before leaves.
Fruit: Thin, wafer-like samara, nearly round, notched at top, 1/2 inch in diameter, initially pale green, later turning light brown when ripe in spring.
Twig: Slender, slightly zigzag, grayish tinged with green; buds are quite small (1/8 inch), dark reddish-gray, round, flower buds are considerably larger.

From Flora of North America:
"Planted for quick-growing windbreaks, Ulmus pumila has weak wood, and its branches break easily in mature trees. It is easily distinguished from other North American elms by its singly serrate leaf margins. Ulmus pumila is similar to U . parvifolia Jacquin with its small, singly serrate leaves. Ulmus parvifolia , however, has smooth bark that sheds from tan to orange, and it flowers and sets fruit in the fall."

Bark

References

Flora of North America, Ulmus pumila
Siberian Elm - Ulmus pumila, Morton Arboretum acc. 325-70*4, photographed July 12, 2007. Photographer: Bruce J. Marlin

Excerpts from Morton Arboretum articles used with permission.

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