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A thicket-forming shrub to about 12 ft high, or a small tree; young stems at first silky, becoming glabrous, or sometimes glabrous from the start. Leaves slender, 2 to 4 in. long, 1⁄8 to 3⁄8 in. wide (but larger and relatively broader on strong shoots), sharply acute to acuminate at the apex, tapered at the base to a very short petiole, clad on both sides when young with grey or silvery hairs, becoming grey-green and often glabrous above, more persistently hairy beneath, margins entire or inconspicuously toothed. Stipules wanting, except sometimes on vigorous shoots. Catkins 11⁄4 to 2 in. long, appearing with the unfolding leaves on short leafy peduncles from the previous year’s wood, or later on leafy laterals of the seaon’s growths, terminal and solitary or supplemented (especially on male plants) by one or two axillary catkins; scales yellow, usually narrow and acute, deciduous. Stamens two; filaments clad with long hairs at the base. Ovary hairy or glabrous, sessile or almost so; stigmas divided, sessile.
Native of W. North America away from the coastal region, extending into Mexico. It is a variable species in itself, and is part of a taxonomically difficult and controversial group. The precise identification of the cultivated plants, which have not been seen to flower in this country, is uncertain, but they appear to belong to S. exigua as interpreted in recent American works. According to the older classifications they might have taken the name S. argophylla Nutt. They are, at any rate, very ornamental with their narrow, silvery foliage and would probably thrive best in a damp, grass-free, sandy soil.
S. interior Rowlee S. longifolia Muhl., not Lam.; S. exigua subsp. interior (Rowlee) Cronquist – Very closely allied to S. exigua but with green leaves and differing in various technical characters. Of wide distribution in America, from the Rocky Mountains to the Atlantic.
The section Longifoliae is confined to the New World. Unlike other willows, they spread widely by suckers from the roots. The catkins, at least the later ones, are borne on long, leafy laterals, often in clusters.