Northern Ontario Plant Database
Salix petiolaris Sm.
En: slender willow, meadow willow
Salicaceae (Willow Family)
The Genus Salix: Willows have slender branches with alternate leaves, winter buds have a single bud scale. The small, unisexual flowers lack sepals and petals, and are arranged on erect to pendant catkins (aments). Plants are dioecious, with unisexual male and female flowers borne on separate plants. Male flowers usually have 2 stamens, female flowers have a single pistil; both have a basal nectary and are subtended by a scaly bract, often bearing long silky hairs. The fruit is a small narrow conical to ovoid or pear-shaped capsule, with the top portion prolonged into a narrower beak The capsule splits into 2 halves, with each side curving backward to release the woolly seeds.
General: A medium to tall, deciduous shrub with few, clumped stems, to 1–3 m tall; twigs yellowish-green, reddish, or dark brown; young twigs covered with short, dense hairs, becoming smooth with age (glabrate).
Leaves: Alternate, simple, pinnately-veined, petiolate. Leaf blade linear-lanceolate to narrow-oblanceolate, 2–7 cm long, to 1.5 cm wide; dark green and lustrous above, glaucous beneath, the lower surface with silky, reddish-brown hairs when young; leaf base tapering (cuneate) to slightly rounded at the base, the apex sharply pointed (acuminate); margins entire, or upper margins usually finely toothed (serrate), less frequently entire; petiole 3–10 mm long; stipules absent.
Flowers: Unisexual, male and female catkins (aments) on different shrubs (plants dioecious); catkins are borne on short leafy branches and appear with the leaves. Staminate catkins 1–2 cm long; pistillate catkins 1-2.5 cm long. Bracts oblanceolate, 1–2 mm long, brown, hairy.
Fruit: A cluster of narrow-conical capsules, each 5–7 mm long, densely covered in fine silky hairs, especially towards the base.
Habitat and Range: Moist to wet meadows, streambanks, lake shores, wet ditches. The slender willow, a southern boreal North American species, occurs across northern Ontario, but is rare north of 50° N (Soper & Heimburger 1982).
Internet Images: Salix petiolaris (formerly known as Salix gracilis) from the Cedar Creek Natural History Area, Minnesota website.
Charts comparing traits of the 6 common willows found in the northern Ontario FECs.
Similar Species: For further information on willows, see the webpages on Salix bebbiana (beaked willow), Salix discolor (pussy willow), and Salix humilis (upland willow), from the borealforest.org website, or the Salicaceae family webpage on the Aquatic and Wetland Vascular Plants of the Northern Great Plains website, part of the USGS Northern Prairie Wildlife Research Center network.
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