Willows deserve more respect. Ubiquitous and prolific plants, they are frequently overlooked probably because they grow in inaccessible wet areas and beside roadside ditches. However, willows are ecologically valuable and excellent wetland restoration plants: they grow rapidly, control erosion on beaches and riparian edges, and provide habitat and food for many species. In Douglas Tallamy’s book, Bringing Nature Home, he identifies willows as one of the top host plants for Lepidoptera species, feeding a large diversity of caterpillars which, in turn, feed other insects, birds, and mammals. Bird activity in willows and the bustle of pollinators around willows in flower are confirmed by Koch in his seminal book, Starting Trees from Seed (see References).
In the Ottawa area, thirteen native willow species grow naturally (Brunton, 2005). Two are trees and the rest are shrubs. Tree species can appear shrub-like if coppiced, prolifically regrowing with multiple stems. Non-native tree willows – particularly Weeping Willow (S. babylonica and S. x sepulcralis) and Hybrid Crack Willow (S. x fragilis) – are often the most common ones found in our region.
Willows can be hard to identify. They show variability within a species and some hybridize readily with others. But with careful observation it’s possible to identify many Ottawa-area willows with some reasonable degree of confidence using leaves, twigs, bark, and even habitat.
Petrie Island is one of the best sites for viewing willow diversity, hosting eight native species and three non-native species.
The descriptions and identification information on this site for each willow is broad and high level, meant to help interested naturalists improve willow field identification and appreciation. Detailed willow id keys and information can be found on-line (University of Michigan) and in comprehensive field guides such as Trees of Eastern North America, a Princeton Field Guide, by Gil Nelson, Christopher J. Earle, and Richard Spellenberg. Both sources were referenced for this write-up.
Willows are deciduous, alternate, with the leaves generally darker and more lustrous above than below. Twigs are usually flexible (but see Black Willow for brittleness of Hybrid Crack Willow) and can occur in a variety of colours (e.g. light green, grey-brown, brown, reddish brown, yellow) even in the same species. Flowers are unisexual catkins on separately sexed plants, blooming locally from April through June.
Native Tree Willows
S. nigra – Black Willow. Uncommon in the Ottawa area and frequently confused with the more abundant and widespread Hybrid Crack Willow (S. x fragilis).
S. amygdaloides – Peachleaf Willow – Widespread, but uncommon, this is our largest willow tree even though it’s growing at its northern range.
Native Shrub Willows
S. discolor – Pussy Willow – One of our most common and easy to identify shrub willows.
S. bebbiana – Bebb’s Willow – A large, common, and widespread shrub willow.
S. humilis – Upland Willow (Prairie Willow) – A small shrub willow that grows in dry conditions.
S. interior – Sandbar Willow – A small shrub willow with distinctive long, narrow leaves that grows in colonies.
S. lucida – Shining Willow – A sprawling shrub willow distinguished by its glossy, dark green leaves.
S. eriocephala – Heart-leaved Willow – Red-tipped new growth, a heart-shaped leaf base, and large stipules characterize this shrub willow.
S. petiolaris – Meadow Willow – A large, upright shrub willow with dark purplish- or reddish-brown mature twigs.
S. candida – Sage or Hoary Willow – A regionally significant shrub willow that prefers calcareous fens and swamps.