Salix_sericea

Salix sericea

Important Synonyms:
Common Name: silky willow

General Remarks
This is an eastern North American species whose range extends south along the Appalachians reaching as far as northeastern Georgia [Argus 2010]. Both morphologically and ecologically it is very similar to S. petiolaris (the latter has a comparatively northern range; see notes to [S. petiolaris]). In recent publications (e.g., Argus 2010), Salix sericea is placed in the monotypic section Griseae (monotypic = containing the only one species). Earlier authors (Fernald and others) attributed other willows, including Salix petiolaris, to Griseae.

Description
Shrub 0.5-4 m tall [1], [2]. Branchlets velvety (velutinous: hairs minute, upright); branches densely tomentose (hairs flatted and matted), becoming glabrate with age, though tomentum often persists near buds, BRITTLE at base. Buds velutinous to puberulent or glabrate, ribbed (keeled) laterally, apex blunt [3]. Leaves narrowly lanceolate to narrowly oblong [4], the larger ones usually 6.5-10 x 1-3-2.5 cm (length-to-width ratio usually 4-6), apex acute to short acuminate, base cuneate (rarely obtuse), margin glandular serrate to serrulate or sometimes crenulate [5], [6]. Lower (abaxial) surface glaucous (often obscured by hairs), densely short-silky [7] to glabrate with age [8]; hairs straight. Upper (adaxial) surface dull, sparsely pubescent to glabrescent. Juvenile blade reddish or yellowish green, very densely short-silky abaxially, hairs white (rarely with some rusty hairs). Petiole 3.5-12 (to 21) mm long, velvety (velutinous) on one side, sometimes with a couple of spherical glands at junction with blade. Stipules mostly small or absent; on vigorous shoots oblong or half-ovate 1.2-4 mm long, with glandular margin. Upper leaf surface without stomata (leaves hypostomatous). Leaf blades often drying dark. Catkins flowering as or just before leaves emerge (coetaneous or subprecocious), with 2-3 leafy bracts at base [9]; floral bracts dark brown or blackish, often pale at base. Pistillate catkins densely flowered, 2-4.5 cm long, ovaries short sericeous, ovate, abruptly tapering to style; stipes and styles short [10] [11].

Recognition
A willow with brittle branchlets and sessile catkins flowering just before leaves (subprecocious). Leaves densely white silky (sericeous) beneath, with short, appressed hairs; upper leaf surface glabrate, dark green. Leaves often blackening on drying [12].
Mature foliage of S. sericea may be confused with that of S. ericephala. Both species have pine cone galls produced by gall midges. S. sericea differs from S. eriocephala in its brittle velutinous branchlets (especially velvety at nodes, between the bud and branchlet) and also by lack of loose inner membrane in buds; leaves typically sericeous beneath, with cuneate base (never cordate as in S. eriocephala), and mostly lacking stipules.
In its vegetative characters, S. sericea is morphologically so similar to S. petiolaris that the two have been sometimes treated as varieties of a single species (see list of synonyms). Their seasonal variation constitutes a major problem for their discrimination. In S. petiolaris leaves, as they unfold, are densely sericeous on both sides, and this indumentum may be partially retained at maturity. On the other hand, mature foliage of sericea may become glabrous, as in S. petiolaris. In the absence of catkins, the two species can be separated by presence of ferrugineous hairs on leaf surface of S. petiolaris and the tendency of that species to have subentire or irregularly serrate leaf margins and narrower leaves. However, some samples cannot be positively identified (Argus 1986: 125). Reports of hybrids S. petiolaris × S. sericea from Massachusetts and Pennsylvania by Schneider were probably based on a densely sericeous variant of S. petiolaris (Argus 2010). It is sometimes named S. ×subsericea but does not seem to be a hybrid (Argus 1986, 2010; Voss 1972-1996, Michigan Flora, vol. 2).

Habitat
Rocky, silty, or sandy banks of streams, often in or near running water; lowland thickets, marshes, fens, sedge meadows, open seepages, lake/pond shores. This is a pioneer species on floodplains along with S. exigua, a strictly alluvial species. S. sericea can also be found in disturbed habitats: in wet successional (abandoned) fields, ditches, and at roadsides.

Sources and References
1. Argus G.W. 1986. The genus Salix (Salicaceae) in the Southeastern United States. Systematic Botany Monographs 9. 170 pp.
2. Argus G.W. 2006. Guide to the Identification of Salix (Willow) in Illinois, Indiana, Ohio, and Pennsylvania. [https://www.researchgate.net/publication ...]
3. Argus G.W. 2010. Salix L. in Flora of North America North of Mexico, Volume 7. Magnoliophyta: Salicaceae to Brassicaceae, pages 23-162. Eds. Flora of North America Editorial Committee. Oxford and New York: Oxford University Press. Online version: [http://www.efloras.org/florataxon.aspx?f ...]


Last time modified 2016-04-26T10:48:33-07:00 (A.Zinovjev & I.Kadis)