Northern Ontario Plant Database

Plant Description

Salix discolor Muhl.

En: pussy willow, large pussy willow, silver willow
Fr: saule discolore, chaton
Oj: baajin, oziisigobimizh

Salicaceae (Willow Family)

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General: A tall deciduous shrub, to 3 m in height, occasionally a tree to 6 m tall. Pussy willow colonies often form along streambanks when broken stems take root and establish in the moist shoreline. There are many species of willows and they can be difficult to identify. Leaf shape and hairiness are good traits to use for identification, but often, flowers or mature fruit are required to make a positive identification.

Stems/twigs: Twigs slender, dark reddish-brown; buds alternate, with a single reddish-brown bud scale enclosing each bud. Flower buds are 2—3 times larger than vegetative buds. In spring, the bud scale splits along the surface adjacent to the stem and soon falls off. Young stems and winter twigs may be finely hairy, but older stems are smooth (glabrous). Leaf scars are broadly U-shaped with 3 bundle trace scars. Occasionally, a large cone-shaped structure forms at the tip of a willow branch. This odd-looking structure is a pinecone willow gall, which develops after a small fly-like insect (the gall midge) lays an egg in the stem's terminal bud. As the larva develops, it releases a chemical that interferes with normal plant growth, causing a large gall to develop. Slicing open one of these galls will reveal a small larva in the centre.

Leaves: Alternate, simple, pinnately-veined, and stipulate; petioles are 6—17 mm long. Stipules are 0.8—12.5 mm broad, minute on early leaves, but large and prominent on the leaves of vigorous shoots. Leaf blades are narrowly elliptic to oblanceolate, 3—8 cm long by 1.2—3.3 cm wide. Emerging leaves are often reddish and densely hairy with white and scattered reddish-brown hairs, but become smooth with age (glabrate). Mature blades are dark green and dull to somewhat shiny above, pale and glaucous beneath. Leaf bases are tapering (cuneate), apices are pointed (acute to acuminate); and margins are flat and entire to slightly crenate or irregularly toothed (coarsely serrate).

Flowers: Unisexual, male and female catkins occur on different shrubs (dioecious); flowering catkins are erect, fuzzy, and appear before the leaves. Male (staminate) catkins are 2.3—5.2 cm long by 1.2—2.2 cm wide; each male flower has 2 stamens subtended by a floral bract, 0.6-1.1 mm long. Female (pistillate) catkins are 2.5—10.8 cm long by 1.2—3.3 cm wide; female flowers have a single hairy pistil on a short stalk (stipe), 1.6—2.7 mm long, a single style, and 2 stigmas; the pistil is subtended by a floral bract, 1.4—2.5 mm long. Floral bracts are oblong, dark brown to black, and have long silky hairs on the outer surface; these hairs, about twice the length of the bracts, give the emerging catkins their fuzzy silver-grey appearance. Small nectaries, 0.7—1.3 mm long, are present in each flower, situated between the stamens or pistil and the axis of the catkin. Unlike most plants with catkins, willow flowers are pollinated by insects rather than wind.

Fruit: An elongate cluster of small ovoid to pear-shaped capsules, each 6—11 mm long, narrowed towards the top and covered with short hairs. Willow capsules split along 2 lines, with each half recurving to expose the minute seeds, which have a woolly coma at the top to aid dispersal by wind.

Habitat: Streambanks, moist to wet meadows, open woods, and wetlands. The pussy willow has a Canadian range that extends from Newfoundland & Labrador to central B.C.; it occurs across Ontario, throughout the Algoma District, and extends as far north as 52°N (Soper & Heimburger 1985).

Similar Species: The upland willow (Salix humilis Marshall) has leaves roughly the same size and shape as those of the pussy willow, but the lower surface of upland willow leaves is densely woolly with matted greyish hairs. Bebb's willow (Salix bebbiana Sarg.) also has leaves with tapering bases, but the leaves are shorter, more elliptic, rugose above with impressed veins, and hairy on both surfaces.