Willows (genus Salix) range from shrubs to trees that the Morton Arboretum lists at up to 100 feet tall. Pinning down the exact species can be tricky, but recognizing that a tree is a willow is much easier. A handful of features, taken together, give it away: the leaves, the buds, the catkins and where the tree is growing.
The short answer: a willow has alternate, long and narrow (lance-shaped) leaves with finely toothed edges, usually paler underneath; buds pressed close to the twig and covered by a single cap-like scale; slender twigs; catkins in early spring, with male and female flowers on separate trees; and seeds carried on cottony fluff in late spring. Willows are among the first trees to leaf out and usually grow near water. Weeping willow has long, hanging branches; black willow has shaggy, gray-brown bark; white willow is a large, upright tree with corky, furrowed bark.
Feature 1: long, narrow, finely toothed leaves
Willow leaves are simple and alternate along the twig. Most are much longer than wide. NC State Extension describes weeping willow leaves as linear-lanceolate, 3 to 6 inches long and only 0.5 to 0.75 inch wide, with finely serrated edges, light green above and grayish green or whitish beneath. The Morton Arboretum describes white willow leaves as 1 to 4 inches long, slender and finely toothed, and black willow leaves as up to 6 inches long and finely toothed.
Fall color is usually yellow. The Morton Arboretum notes willows are among the first plants to leaf out in spring.
Feature 2: the single bud scale
This is one of the best winter clues. NC State Extension notes willow buds are enclosed in a single cap-like scale. Look closely at a twig with a hand lens: instead of a bud made of several small overlapping scales, you will see one smooth scale covering the whole bud, like a tiny hood.
Feature 3: catkins and cottony seed
Willows are dioecious: male and female flowers grow on separate trees, as the Morton Arboretum and NC State both note. Flowers appear in early spring as catkins. The Morton Arboretum notes that on white willow, the male flowers are the showy ones. NC State describes weeping willow’s male catkins as 1 to 2 inches long, made only of stamens, with no petals.
On female trees, the fruit is a small capsule that splits to release many tiny seeds attached to cottony fluff. NC State notes weeping willow capsules ripen in late May to early June.
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Feature 4: twigs and bark
Willow twigs are slender. NC State describes weeping willow stems as smooth and reddish to yellowish brown. Golden weeping willow, the Morton Arboretum notes, is named for its brilliant yellow twigs.
Bark varies by species and age:
| Willow | Bark |
|---|---|
| Black willow | Gray-brown, furrowed into shaggy plates at maturity |
| White willow | Brown to yellow-brown, corky and furrowed |
| Weeping willow (S. babylonica) | Gray-brown or gray-black, irregularly furrowed |
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Feature 5: where it grows
Willows love water. The Morton Arboretum notes black willow is common in wet areas and tolerates very wet sites, and that white willow is very tolerant of wet sites. A fast-growing tree with narrow leaves beside a pond, stream or ditch is very likely a willow.
Common willows compared
| Willow | Size | Key features |
|---|---|---|
| Weeping willow (Salix babylonica) | 30 to 50 ft tall and wide (UF IFAS) | Long, drooping branches; narrow 3- to 6-inch leaves; native to China |
| Golden weeping willow (Salix alba ‘Tristis’) | 50 to 75 ft tall and wide (Morton) | Weeping form with bright yellow twigs |
| White willow (Salix alba) | 75 to 100 ft tall (Morton) | Upright form; slender leaves; native to Europe and Asia |
| Black willow (Salix nigra) | 30 to 60 ft tall (Morton) | Native to the eastern US; shaggy gray-brown bark; leaves up to 6 inches |
Willow look-alikes
- Poplars and aspens are in the same family (Salicaceae) and also have catkins, but their leaves are much broader. See whether poplar and aspen are the same.
- Willow oak has narrow, willow-like leaves, which NC State describes as 4 to 5 inches long and 1 inch wide, but they have smooth, wavy edges and a bristle at the tip, and the tree bears small acorns. It is an oak.
- Other weeping trees, such as weeping cherries, share the drooping shape. Check the leaves and buds rather than the outline.
Once you know it is a willow
Willows grow fast and have weak wood. The Morton Arboretum lists black, white and golden weeping willow among trees whose roots are prone to invading sewer pipes, and UF IFAS advises keeping weeping willows away from underground water and sewer lines and septic drain fields. Before planting, read how far a willow should be from a house. For upkeep, see when to prune a willow, and if yours is dropping leaves, see why weeping willows lose leaves.
Sources
- Salix babylonica (Weeping Willow), NC State Extension Gardener Plant Toolbox
- Salix babylonica: Weeping Willow (ENH-734), University of Florida IFAS Extension
- Black Willow, The Morton Arboretum
- White Willow, The Morton Arboretum
- Quercus phellos (Willow Oak), NC State Extension Gardener Plant Toolbox
- Golden Weeping Willow, The Morton Arboretum
Top photo: Matt Lavin, CC BY-SA 2.0, via Wikimedia Commons