Salix scouleriana

Scouler's willow


The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta (flowering plants). Class - Magnoliopsida (dicotyledons). Subclass - Dilleniidae. Order - Salicales. Family - Salicaceae (willow). Genus - Salix L. Species - Salix scouleriana Hook.

Ecology: Scouler willow is a shade intolerant, persistent seral species. It is often a minor understory component in a variety of forest types, occurring as scattered individuals in small openings. However, it increases after disturbance, including clearcutting, prescribed fire, soil disturbance, and wildfire. Scouler willow is an early to mid-seral species. Where not already present, it rapidly invades disturbed sites facilitated by its wind-dispersed seed, or sprouts following canopy removal. It capitalizes on moderate to severely burned sites. In clearcuts and young stands it forms a tall shrub layer, comprising a substantial percentage of the plant cover. In some areas, Scouler willow may dominate early seral plant communities following fire or clearcutting and on river terraces and gravel bars.


Habit: Shrub, slender tree, < 10 m. Stem: twigs yellow-green or -brown, twigs sparsely hairy to densely velvety. Leaf: stipules generally leaf-like; petiole 2--13 mm, generally velvety; young leaves hairy; mature blade 29--100 mm, obovate or oblanceolate to narrowly elliptic, acuminate (base wedge-shaped or convex), entire or crenate, generally strongly rolled under, abaxial hairs sparse to dense, short- or long-silky or woolly, white or white and rusty, wavy or straight. Inflorescence: blooming before leaves, pistillate 18--60 mm, on leafy shoots 0(8) mm; flower bract dark brown or 2-colored. Staminate Flower: stamens 2. Pistillate Flower: ovary silky, stalk 0.8--2.3 mm, style 0.2--0.6 mm.


Fire effects: Willows are greatly favored by fire in most habitats. As a survivor and off-site colonizer, Scouler willow is abundant following fire and has a moderate regeneration period. It is adapted to fire by rapidly resprouting from the root crown, and establishes from seed on severely burned sites. Wind dispersed seeds facilitate rapid recolonization of burned areas. Stand replacing fires favor regeneration of Scouler willow, and good response from Scouler willow seedlings can be expected on sites where fire damage is thorough enough to expose mineral soil. Without fire, closing conifer canopies lead to the deterioration of Scouler willow. In dense second growth stands of sequoia in California, Scouler willow debris creates a fuel hazard; formerly abundant stands of Scouler willow grew in dense clones that were shaded out and killed, forming dense tangles of fuel for wildfire.


Seedling establishment and plant growth - Scouler willow probably begins producing seed before 10 years of age. Insects, especially bees, are important pollinators. Seeds disperse in late spring, disseminated by wind and water. These seeds have cottony hairs that allow them to travel long distances. Seedlings may regenerate from windborne seed from as far as several miles away. Scouler willow seeds are nondormant and remain viable for only a few days without moisture. Willow seeds are characterized by a short seed life and rapid germination, and Scouler willow seeds usually germinate within 12 to 24 hours of dispersal. The seeds are scarified by light burning and moist mineral soil is required for germination and seedling establishment.

Vegetative regeneration - Scouler willow regenerates asexually by vigorously sprouting from a subterranean root crown. This basal sprouting occurs in response to disturbance, including fire, flooding, and mechanical damage. Scouler willow sprouts typically have a tall, fast growth response.

Species Distribution


USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

Flora of North America
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 19+ vols. New York and Oxford.

The Jepson Herbarium
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA.

Burke Museum of Natural History and Culture
Burke Museum. 2016 [Online]. University of Washington.