- Name also: Crack-willow, Brittle Willow
- Latin synonym: Salix fragilis
- Family: Willow Family – Salicaceae
- Growing form and height: Tree. 6–20 m (20–65 ft.).
- Flower: Male and female flowers on separate plants. Inflorescence a hairy, long, slender, and nodding catkin. Individual flowers in axils of catkin scales, small, lacking perianth. Catkin scales pale, soon falling. Stamens 2 (3), base of filaments hairy. Pistil formed from 2 fused carpels.
- Leaves: Alternate. Stalked, stipulate, stipules cordate, hairless, soon falling. Leaf-blade 10–12 cm (4–5 in.) long, narrowly elliptic, tapering to a long point, finely glandular-serrate, hairless, glossy and deep green above, bluish-green and prominent-veined beneath. Vein pairs 12–15.
- Buds: Hairless, glossy, brown.
- Fruit: Two-valved capsule containing many plumed hairs.
- Habitat: An ornamental. Sometimes an escape or remaining after cultivation in old villages and former settlements.
- Flowering time: June. Flowers when already leafy.
Willows are insect-pollinated, sympodially growing, dioecious trees, shrubs, or dwarf shrubs. Their buds have a single protective scale, and their leaves are entire and stipulate. The inflorescence is a catkin which falls off in one piece. Hybrids between willow species are common.
Crack willow is not native in Finland, but originally an ornamental. It is a tree which has a stout trunk and flowers after coming into leaf. The branches are hairless, yellowish-brown, glossy, and easily breaking from the base. A locally popular ornamental is the cultivar S. euxina ´Bullata´ which has a beautifully rounded crown.
Willows are a group of 400 to 500 woody species. They occur in all continents apart from Antarctica. Willows so closely resemble poplars (Populus) that they are thought to be descended from similar ancestors. Those willows which have several stamens, such as bay willow (S. pentandra), occurred already in the Tertiary, and are most similar to the poplars. The more highly evolved willow species which have only two stamens seem to have increased only after the ice age. Most of the Finnish species belong to this group. Willows are of economic importance e.g. as raw material in basketry and as a source of tannins. In addition, the bark yields salicine, a medicinal substance.