Flower:

Male and female flowers are on separate plants (dioecious) in spike-like clusters (catkins) at the tips of short branchlets along 1 year old branches, emerging just before or with the leaves. Male catkins are oval to nearly round, 2/3 to 1½ inches long, the flowers densely packed, each flower with 2 stamens, the tips (anthers) initially red to purple, turning yellow. Female catkins are ¾ to 2½ inches long, the flowers moderately to densely crowded on the spike, narrowly pear to horn-shaped, densely covered in woolly hairs, and on slender stalks .1 to 1.2 mm long. At the base of each male and female flower stalk is a tiny, yellowish to brown scale-like bract densely covered in straight or wavy hairs.

Leaves and stems:

Leaves are alternate, 1¾ to 4 inches long, to ¾ inch wide, 4.5 to 11 times as long as wide, mostly narrowly elliptic and widest near the middle, pointed at the tip, wedge-shaped to somewhat rounded at the base, mostly toothless, the edges often rolled under (revolute). The upper surface is dark green, sparsely to moderately covered in cobwebby hairs, with a strong network of indented veins; the lower surface is silvery-white from a dense covering of woolly hairs.

At the base of the short leaf stalk is a pair of leaf-like appendages (stipules) that are up to 3.6 mm long and pointed at the tip. New leaves are yellowish and woolly-hairy. New branchlets are yellowish-brown or red-brown, densely covered in short or woolly white hairs, becoming brown and mostly hairless the second year. Stems are multiple, few-branched, slender with smooth to rough, gray-brown bark. Loose colonies may form by a process known as layering, where a branch that touches the ground takes root and forms a new plant, detaching itself from the parent plant.

Fruit:

The spike elongates some as fruit matures, the fruit becoming more loosely arranged than the flowers. Fruit is a capsule 4 to 6 mm long, yellowish to light brown when mature, covered in woolly hairs, narrowly pear to horn-shaped with a long, straight to slightly curved beak. The capsule splits into two halves when mature, releasing the cottony seed.

Notes:

There are over 20 species of Willows in Minnesota; Sage-leaved Willow is a common, low to mid-sized shrub of fens, conifer swamps, floating mats and similar wetlands, often in calcareous soils. It is a fairly distinct species, recognized by the narrow leaves that are woolly white on the underside, mostly toothless and typically rolled under along the edges (revolute), obvious stipules that are hairy like the leaves, and woolly-hairy fruit 4 to 6 mm long. It is typically under 3 feet tall with few leafy branches.

The leaves of Sage-leaved Willow are similar to Satiny Willow (Salix pellita), which is a larger shrub or small tree with leaves that are more glossy on the upper surface, hairs on the lower surface are silky and mostly straight, stipules are minute or absent, twigs are mostly hairless and usually covered with a waxy bloom, and fruit is covered in short silky hairs. Sage-leaved Willow also vaguely resembles the smaller Prairie Willow (Salix humilis var. tristis), which is also short statured with woolly-hairy leaves, but its leaves are smaller and proportionately broader, mostly widest near the tip, and it lives in dry habitats.

Sage-leaved Willow is known to hybridize with several other willows; hybrids are usually recognized by woolly hairs or patches of woolly hairs on leaves, stems, female flowers and fruits. The single hybrid recorded in Minnesota was with Pussy Willow (Salix discolor) at a Hennepin County park in 1915, so hybrids are rare, or at least rarely recognized.