Friday, March 2, 2012

Tree of the Week

Siberian Elm, Ulmus pumila L.

DISTINGUISHING CHARACTERISTICS: Leaves simple, alternate, elliptic to elliptic-lanceolate, 1 to 3 inches long with petioles 1/16 to 1/8 inch long, toothed; base slightly unequal; upper surface glabrous; lower surface glabrous or nearly so; veins running directly into the teeth. Winter twigs very slender, light gray or gray-green, glabrous or nearly so; leaf scars very small, otherwise similar to slippery elm. Buds ovoid or globose, 1/16 to 3/16 inch long, the terminal absent; scales 6 to 10, dark purple-brown, shiny, glabrous except for white hairs along their margins. Flowers green, very small, perfect, without petals, on stalks about 1/16 inch long, appearing in crowded, umbellike clusters before the leaves unfold in spring. Fruit a 1-seeded, nearly round samara about 1/2 inch in diameter; wing glabrous, shallowly notched, seed cavity distinct. Bark gray-brown, shallowly furrowed with long scaly ridges, uniformly red-brown in cross section.

SIMILAR TREES: Other elms have much larger, doubly toothed leaves and larger buds.

IOWA DISTRIBUTION: Cultivated throughout the state, often escaping to waste places. Hybrids between this species and the slippery elm are sometimes encountered.

Forest and Shade Trees of Iowa: Third Edition, by Peter J. van der Linden and Donald R. Farrar

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