Siberian Elm is an introduced and naturalized invasive medium size tree growing to 70 feet high with an open crown, but often badly formed due to limb breakage and sprouting along the trunk. The wood is very brittle.
The bark is gray to brown becoming irregularly furrowed with interlacing ridges and usually streaked with lighter stains from a bacterial infection.
Twigs are slender, slightly zigzag, grayish-green, leaf buds are small and round (about 1/8 inch) while the flower buds are also round but larger, both with very dark reddish-black scales which, on the flower buds, can have fine hair.
The leaves are alternate, narrowly elliptic to ovate, stalked, 2 to 3 inches long, no more than 1 inch wide, with a singly-toothed (saw-toothed) margin, dark green on top and smooth whereas the underside is paler, usually smooth but may have some hair in the vein axils. The lateral veins fork up to 3 times per side. The leaf tip is pointed and the base is more rounded than other elms and mostly symmetrical. Fall color is a dull yellow.
Flowers of Siberian Elm, like all of the Ulmus genus, are bisexual, appearing before the leaves. The flowers form in tight clusters (fascicles) along the twigs, opening erect with (3) 6 to 15 un-stalked flowers per cluster, each flower with 4 or 5 shallow calyx lobes and no petals; 4 to 8 stamens with reddish-brown anthers, a green pistil with a long divided style. Flowers are pollinated by the wind.
Seed: The fertile flowers form a wafer-like almost round single seeded samara, about 1/2 inch in diameter, most of the diameter is a broad thin wing. These are a creamy-yellow turning brown at maturity. The papery wing of the samara is NOT hairy on the edges; the the tip is notched from 1/3 to 1/2 of its length. The seed itself is thickened but not inflated. These mature rapidly in late spring to early summer and are dispersed by the wind. They can germinate immediately and the prolific seed production can produce many small trees in areas not controlled by mowing.
Habitat: Siberian Elm in its native habitat grows in moist soils along stream edges. It has a widely spreading root system. In North America it has been planted as a landscape plant and as a windbreak, being adaptable to various soils in sunny conditions. It is resistant to the Dutch Elm disease that has devastated the native American Elm. It is subject to wilts, rots and elm leaf beetles.
Names: The genus Ulmus, is the Latin word for Elm. the species name, pumila, means 'dwarf' and refers to the small leaf of this species compared to other members of the genus. This is where the alternate common name of 'dwarf elm' arises. The author name for the plant classification, 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: U. pumila is similar to Chinese Elm, U. parvifolia, but there the bark is smooth and sheds in irregular tan to orange plates; grows in shade and flowers and fruits in the fall. Other native elms in our area, such as American Elm and Slippery Elm, have leaves with more un-symmetrical bases and the leaf margins are double toothed. American Elm flowers are stalked.
Above: Photos 1 and 2 - Trunk and bark detail. 3rd photo - Siberian Elm growing with a group of Cottonwoods.
Below: The leaf base is more rounded and symmetrical than other elms. Margins are not double toothed. The upper side is dark green and smooth. The underside (2nd photo) is paler in color. Leaves are smaller than other elms, usually not more than one inch wide.
Below: Several lateral veins fork at the margins. Veins are prominent on the underside.
Below: Buds have dark reddish-black scales. Flower buds are larger with some fine hair on the scales. The leaf buds (2nd Photo) are smaller compared with he flower bud shown in the center.
Below: Flower buds opening. Stamen anthers are reddish in pollination, turning black after pollination. The styles are divided.
Below: 2nd photo - The mature samaras are rounded, without hair and a small notch at the tip.
Below: Fully formed samaras.
Siberian Elm has never been recorded as present in the Eloise Butler Wildflower Garden. It is native to Asia and China and is one of four species of Elm found in Minnesota: U. americana, American Elm; U. pumila, Siberian Elm; U. rubra, Slippery or Red Elm; and U. thomasii, Rock or Cork Elm. In North America, U. pumila is found throughout the United States and most of the lower Canadian Provinces. Because of its original use for windbreaks it is found in the majority of counties of Minnesota with scattered exceptions.
Uses: While originally imported in the 1860s for its fast growth and adaptability to various soils. It is still sold as a windbreak tree, but it is not recommended for landscape use due to its brittle wood which results in wind damage and poor shape. It also freely self-seeds and becomes invasive in our area.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"