Populus deltoides

Eastern cottonwood is dioecious; flowers are either male or female and occur on separate trees. The flowers, whether staminate or pistillate, are produced on catkins 2-3″ long; the flowers are wind pollinated. Male catkins are produced in clusters of 2-4 near branch tips; they are bright red or yellow, cylindrical, and densely covered with male florets. The male florets have a fringed bract at their base, above which is a basal disc with 30-40 reddish or yellowish stamens. Female catkins are solitary (not in groups), cylindrical, and green, covered with numerous female florets on slender petioles. Each female floret rests on a fringed bract above which is a dish-shaped three- or four-carpelled basal disc with a single, oval pistil about 8 mm long with 2-4 apical, yellowish, flattened stigmas with undulate margins. After fertilization, the female catkins elongate to a length of 4-6″ while individual ovaries enlarge; at maturity, each fruit splits to release 30-50, 2 mm long, seeds suspended on cottony hairs. The seeds are both wind and water dispersed.

Eastern cottonwood (a.k.a., plains cottonwood, Populus deltoides) is a native deciduous tree that can reach heights of 60-120 feet at maturity with a trunk as much as 11.5 feet in diameter. These are not long-lived trees, despite their size — a 75-year-old cottonwood is elderly. The bark of the trunk is light or ash brown and deeply furrowed; the bark on the branchlets is initially yellow-brown, becoming tan by their third year. The leaves of Eastern cottonwood are distinctive — rather than having petioles that are round or oval in cross section, the petiole of Eastern cottonwood leaves is laterally flattened distally (i.e., flattened in a plane at right angles to the plane of the leaf blade), usually with a pair of small glands on the leaf blade where the petiole joins the blade. It has been suggested that this flattening permits the leaf to flutter in the slightest breeze, presumably helping keep the leaf temperature low enough for efficient photosynthesis. The leaves themselves are alternate, 4-5″ long and 3-4″ across, shaped like an equilateral triangle with a slender tip; there are slightly hooked teeth around the leaf margins. The upper leaf surface is medium green in color; the lower leaf surface is pale green and dull. Cottonwoods depend on their seeds lodging near enough a persistent body of water or stream that the seeds can germinate and prosper. Indeed, it is an interesting exercise to map the locations of the cottonwoods in Hyde Park. Most of the local cottonwoods are reaching the end of their expected lifespan (about 100 years), but a map of the trees will reveal streams in Hyde Park that have long since been diverted into culverts or concreted over, their course shown today only by the cottonwood saplings they nurtured a century ago.

Eastern cottonwood (a.k.a., plains cottonwood, Populus deltoides) is a native deciduous tree that can reach heights of 60-120 feet at maturity with a trunk as much as 11.5 feet in diameter. These are not long-lived trees, despite their size — a 75-year-old cottonwood is elderly. Cottonwoods depend on their seeds lodging near enough a persistent body of water or stream that the seeds can germinate and prosper. Indeed, it is an interesting exercise to map the locations of the cottonwoods in Hyde Park. Most of the local cottonwoods are reaching the end of their expected lifespan (about 100 years), but a map of the trees will reveal streams in Hyde Park that have long since been diverted into culverts or concreted over, their course shown today only by the cottonwood saplings they nurtured a century ago.