April 8, 2016

Winter's End

By Eric D'Aleo

Sometimes winter seems to last forever. The accumulation of snow, the bite of cold wind, and the short, gray days are enough to make anyone succumb to Seasonal Affective Disorder. Even with teasing sunny days and thawing ice, cold temperatures sneak back in to solidify winter’s hold once more and make us doubt spring’s eventual arrival. We search for some sign of change and the “bloom” of pussy willows provides encouragement to cope through the last throes of winter.

Pussy willows (Salix discolor) are native to the northern United States and are found from Idaho east to Maine and as far south as Maryland. There are 30 species of willows throughout North America and many have the ability to hybridize with one another, making identification difficult in some regions. Pussy willows are a large, multi-stemmed shrub that grows as high as twenty feet with a dark gray, scaly bark. They are found most often in wetlands, along river banks, or in drainage ditches beside roadsides. Although they may sometimes be found in upland areas, they prefer to grow in wet soils. The long narrow-toothed leaves are green on the surface and downy grayish-white underneath.

However, it’s the flowers, the soft silvery catkins which appear first that captures our attention. The catkins are dioecious, meaning male and female flowers form on different plants. Male catkins develop golden yellow stamens as they mature, and they open first. The soft, silvery bud of hairs, that people find so appealing, is used to insulate and protect the developing reproductive parts. The temperatures in early spring can still be quite cold but the hairs of the catkin trap the sun’s heat and raise the temperature several degrees. This aids in the development of pollen in the male catkins. The slender green pistils on female catkins develop later but also have similar hairs that raise the temperature of the ovules maturing inside. Once fully open, the male catkins have yellow pollen on their tips while female catkins are less colorful. The flowers produce large amounts of nectar high in sugar content, which attracts bees, flies, ants, and other pollinating insects that have emerged from their winter dormancy in search of food. Once pollinated, the seeds develop in small capsules on the female catkins. Each contains numerous seeds embedded in cottony down. The seeds are released to the wind in summer and are carried to a new location where, if conditions are right, they may germinate.

Many animals rely on the pussy willow shrubs besides insect pollinators. At least five species of butterflies and moths feed on the plant during their larval stage. These include the viceroy (Limenitis archippus) and mourning cloak (Nymphalis antiopa) butterflies. Hairstreaks (Strymon spp.), sphinx moths (Sphingidae), and comma moths (Polygonia comma) also feed on willows. Leafrollers, sawflies, borers, midges, beetles, and gall gnats also feed on foliage of the pussy willow. Birds including catbirds, chickadees, goldfinches, warblers, and flycatchers are attracted to the shrubs to feed on the insect life found there. Willow thickets may provide cover and nesting opportunities for songbirds, northern harrier hawks, waterfowl, and marsh birds. Pussy willow buds provide an important winter food source for ruffed grouse and they may also be eaten by squirrels. Porcupines eat the bark and the end of twigs in the winter and also feed on catkins during spring. Snowshoe hare and cottontail rabbit gnaw off bark or feed on twigs in winter, while both moose and white tailed deer browse on the twigs of pussy willow and other willow species during winter.

Pussy willow has been important to people, not only as a harbinger of spring, but also as a natural resource. Its pliable branches are used to construct wicker mats, baskets, and cradles. It contains the compound ‘salicin’ in its bark, like all willows, and was historically used by Native North Americans as a natural pain reliever and fever reducer. An important use today is for use in stabilizing banks and shorelines along water bodies, binding soil with its extensive root system. This, along with the ability of willow cuttings to root quickly, allows pussy willow to thrive in seasonally flooded areas. As a result willow filter strips are planted in agricultural areas to reduce sediment and nutrient runoff into nearby wetlands or water bodies.

Who knew an early sigh of spring also was so beneficial to people and the natural world?

Bonus: Check out this video of a porcupine eating pussy willow catkins: https://vimeo.com/23759207

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