Fishtales - Spring 2006

The Nooksack Salmon Enhancement Association

Focus on a riparian plant: Black Cottonwood
by Emily Nuchols

Black cottonwood (Populous balsamifera ssp. Trichocarpa) is a large, deciduous tree that can reach up to 50 meters tall. The tree is found at low to medium elevation in moist or wet sites; it is commonly found in the riparian area.

Cottonwoods form stands on floodplains and along major rivers and on disturbed upland sites. They are exceptionally tolerant of flooding erosion and flood deposits filling around the trunk.

A certain amount of water erosion along the stream bank is natural and healthy for the ecosystem. Too much erosion can cause problems, clog streams with gravel, fill the water body with sediment and reduce water quality. Most erosion occurs during times of flooding when more, faster moving water is can carry a larger sediment load.

The bark of mature cottonwood trees is dark gray and has deep grooves. The branches are covered in thick, oval, deciduous leaves.

Leaves have a rounded base and are pointed at the tip. The tops of the leaves are a glossy green and the bottoms are pale and many times have stained patches of brown resin beneath.

Both male and female flowers in catkins, and are on separate trees. The buds are full of resin, very sticky and fragrant. Male flowers have 40 to 60 stamens (the male organ of a flower). Each stamen usually has a stalk called the filament, and an anther on top of that.

The anther is often composed of four pollen sacs called microsporangia, which produce pollen. The female flowers have three stigmas. Insects gather pollen and transfer the pollen from male to female trees causing pollination.

Cottonwoods produce fruits in round, green capsules that split open into three parts when ripe. The seeds are covered with fluffy, white hairs, giving the cottonwood its name. The cottony structures allow seeds to be blown long distances in the wind before settling to the ground.

American Indians used the buds as a poultice for lung pains and rheumatism. The old, rotten leaves were boiled and used in a bath for body pains and stomach trouble. Cottonwood was thought to be an antiseptic plant. Bruised leaves were placed on cuts and an infusion was made from the bark for sore throats. The resin from the buds was used for baldness, sore throats, whooping cough and tuberculosis.

The Chehalis believed cottonwoods had a life of their own because they often quake, even when there is no wind.