Immature anthers of Black Cottonwood, Populus trichocarpa, develop in the male flower. When fully developed in early springtime the anthers split open and release their pollen. Twigs with dormant buds were collected on 25 November, 2004, at Eagle River, Alaska and were brought indoors. The flower buds opened for this photo in 5 days. The field of view is 2 mm wide.
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Black Cottonwood tree. 6 April, 2003, at Eagle River, Alaska.

Unfolding Cottonwood leaves push through the bud scales that protected them over the winter. 30 May, 2002 on the shore of Kenai Lake, Alaska.

Cottonwood twigs. 30 May, 2002, Kenai Lake, Alaska.

Black Cottonwood trees are the largest hardwood trees in northwestern North America as well as in Alaska. These trees grow rapidly and can attain their maximum height of 38 meters (125 feet) in 35 years (Viereck 1972). The largest specimens may have trunks nearly 3 meters in diameter, but the trees at the Eagle River Nature Center, although 30 meters tall, are usually one meter or less in diameter.

Cottonwood trees produce, resinous, aromatic flower and leaf buds that can be used to make balms and incense. Male and female flowers bloom on separate trees. The Denaina use winter buds to produce a medicinal salve that is used to treat frostbite, sores, and rashes (Kari 1995). The long, drooping inflorescence called a catkin (or ament) may contain 50 flowers. The male flowers each produce twenty or more stamens each with a four-chambered anther, while the female flowers possess three parted ovaries that produce many cottony seeds. The flower buds break dormancy in early spring and the flowers mature before the leaves come out.