Ulmus pumila

Ulmus pumila, the Siberian elm, is a tree native to Asia. It is also known as the Asiatic elm and dwarf elm, but sometimes mistakenly called the "Chinese" elm (Ulmus parvifolia). U. pumila has been widely cultivated throughout Asia, North America, Argentina, and southern Europe, becoming naturalized in many places, notably across much of the United States.

Description

The Siberian elm is usually a small to medium-sized, often bushy, deciduous tree growing to 25 m (82 ft) tall, the diameter at breast height to 1 m (3 ft 3 in). The bark is dark gray and irregularly longitudinally fissured. The branchlets are yellowish gray, glabrous or pubescent, unwinged, and without a corky layer, with scattered lenticels. The winter buds are dark brown to red-brown, globose to ovoid. The petiole is 4–10 millimetres (1⁄4–1⁄2 inch) and pubescent; the leaf blade is elliptic-ovate to elliptic-lanceolate, 2–8 by 1.2–3.5 centimetres (3⁄4 in–3+1⁄8 in × 1⁄2 in–1+3⁄8 in), the colour changing from dark green to yellow in autumn. The perfect, apetalous, wind-pollinated flowers bloom for one week in early spring, before the leaves emerge, in tight fascicles (bundles) on the last year's branchlets. Flowers emerging in early February are often damaged by frost (causing the species to be dropped from the Dutch elm breeding programme). Each flower is about 3 mm (1⁄8 in) across and has a green calyx with four or five lobes, four to eight stamens with brownish-red anthers, and a green pistil with a two-lobed style. Unlike most elms, the Siberian elm is able to self-pollinate successfully.

The wind-dispersed samarae are whitish tan, orbicular to rarely broadly obovate or elliptical, 1 cm–2 cm × 1 cm–1.5 cm (3⁄8 in–3⁄4 in × 3⁄8 in–5⁄8 in), and glabrous except for pubescence on the stigmatic surface; the stalk is 1–2 mm (5⁄128–5⁄64 in), and the perianth is persistent. The seed is at the centre of the samara or occasionally slightly toward the apex, but does not reach the apical notch. Flowering and fruiting occur from March to May. Ploidy: 2n = 28. The tree also suckers readily from its roots.