The willow (Salix) collection is perhaps not the showiest of the Arboretum’s plant collections, but in late winter and early spring it provides vital rays of hope after a long cold season (okay, this winter has been pretty mild, but just think back to how you were feeling last March). Willows, which are primarily dioecious (male and female flowers are borne on separate plants), include some of the earliest bloomers at the Arboretum. Both the male and female flowers (which lack petals and sepals) occur in short, dense racemes known as catkins. Individual flowers are set on scales which, in some species, sport a thick fringe of silky hairs, most notably on male catkins.
Willow species with especially furry catkins are commonly called pussy willows. The most spectacular of these at the Arboretum is rosegold pussy willow (S. gracilistyla), an eastern Asian species with very large, silvery male catkins. Every year I look forward to their emergence on several specimens (690-75, 930-74) along Meadow Road; I and many other visitors can’t resist petting the catkins, which are indeed as soft as a kitten. Two specimens of a related species, black pussy willow [pdf] (S. gracilistyla var. melanostachys; 404-82, 71-98), grow nearby, but you’d never guess the relationship by looking at the catkins. Black pussy willow’s catkin scales lack silky hairs and are such a deep purple they appear black.
This year’s early warmth has already pushed many of the pussy willows through blooming, but the willow collection’s other post-winter treat — early leaf emergence — is on the way. Many willows leaf out well before most other tree species at the Arboretum (somewhat surprisingly, these same willows are often among the last to lose their leaves in autumn). The willow collection lies mainly in the moist soils in and around the Meadow area, and one of my favorite times each year is when the first haze of fresh, bright green emerges on the willows framing the Meadow. Though most other trees are still bare then, the willows prove that winter is over and a new growing season has arrived.