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Plant Description


Ulmus americana L.

En: white elm, water elm, American elm
Fr: orme d'Amérique, orme blanc, orme à larges feuilles
Oj: aniib., niip

Ulmaceae (Elm Family)

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Ulmus americana1 Ulmus americana2 Ulmus americana3 Ulmus americana4 Ulmus americana5 Ulmus americana6 Ulmus americana7 Ulmus americana8 Ulmus americana9 Ulmus americana10 Ulmus americana11 Ulmus americana12

General: A large deciduous tree, 20—35 m tall, with a spreading crown ending in gracefully drooping branches, easily recognized by its vase-shaped profile. White elm trees are moderately shade tolerant; the root system is shallow and widespread in wet soils, but deeper in drier soils; stumps often produce stump sprouts after cutting. Its wood is used for hockey sticks, furniture, and timber. White elm is very susceptible to Dutch elm disease, caused by a wilt fungus, Ophiostoma ulmi(Buism.) Nannf. (formerly Ceratocystis ulmi). Prior to the introduction of this disease to North America, white elm trees were frequently planted as street or shade trees.

Stems/twigs: Twigs are light brown and smooth (glabrous) or hairy; buds are alternate, lanceolate-ovate, sharply pointed (acuminate), slightly flattened, about 5 mm long, and scaly; the 6—9 imbricate bud scales are reddish-brown with dark brown hairy margins. Terminal buds are lacking; the pseudoterminal bud is bent back, away from the leaf scar. Lateral buds are placed off-center to the oval to semicircular leaf scar, which is covered by a thin corky layer and impressed with 3—6 bundle trace scars arranged in 3 groups. Flower buds are broadly ellipsoid, plump, and larger than the leaf buds. The bark of mature trees has flat grayish-brown to dark gray ridges separated by light reddish-brown furrows.

Leaves: Alternate, simple, pinnately-veined with 12—20 pairs of veins, asymmetrical, and petiolate; the short petiole is about 5 mm long. Young leaf blades are finely hairy; mature leaves are glabrous to rough (scabrous) above with short stiff hairs and downy beneath, at least with tufts of hairs in the axils of the midrib and secondary veins. Leaf blades are elliptic to obovate, 5—15 cm long by 3—7.5 cm wide, dark green above, paler beneath. Leaf bases are asymmetric, with one side tapering, the other side rounded to cordate; apices taper abruptly to a sharp point (acuminate); margins are double-toothed (double-serrate). Leaves turn yellow in autumn.

Flowers: in small lateral clusters (fascicles) of 3—5 flowers, each on a long pendant stalk (pedicel), 1—2 cm long. Flowers have a shallowly-lobed light green to reddish calyx with ciliate margins; petals absent; 7—9 stamens with red anthers, and a single pistil with a superior ovary and 2 styles. Flowers bloom in early spring, well before the leaves emerge.

Fruit: A flat papery elliptic to obovate winged samara, yellow-green to light brown, 1—1.2 cm long, glabrous on the surface, but with ciliate margins; the samara wing is notched at the apex forming two incurved teeth. Fruits mature in spring.

Habitat and Range: Rich deciduous and mixedwood forests in valleys, old fields, wetland margins, streambanks, and flood plains. White elm is native to temperate and boreal forests of eastern North America; its Canadian range extends from Nova Scotia to southern Saskatchewan. White elm is found throughout most of the Algoma District; it also occurs throughout southern and eastern Ontario, as well as southern portions of northwestern Ontario.

Similar Species: The rock elm (Ulmus thomasii Sarg.), native to eastern and southern Ontario, also has samaras with ciliate margins, but can be distinguished by the corky ridges on older branches, flowers arranged in elongate racemes, and samaras that are hairy on the surface, as well as the margins. Slippery elm (Ulmus rubra Muhl.), native to portions of eastern and southern Ontario, has hairy leaves, short-stalked flowers and fruit, and nearly orbicular samaras with entire margins.

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