Eastern Cottonwood Fact Sheet
Family: Salicaceae - Willow family
Latin name: Populus deltoides
Common name: Eastern cottonwood
Most photos on this page are of a tree in Naperville, Illinois, along the west branch of the DuPage River.
Click on second leaf photo for enlargement to see flattened stem and glands at base of leaf.
- Male and female flowers develop on separate trees. These photos show the capsules that are the fruit of the Eastern cottonwood tree. Female flowers elongate to 15 to 30 cm (6 to 12 in).
- The capsules have short stalks and grow on long catkins. Each capsule has 3 or 4 valves. The "cottony" material inside the capsule helps the wind carry the seeds. There may be 30 to 60 seeds per capsule.
- The leaves of Populus deltoides are triangular. They are 3 to 5 inches long and nearly as wide. They are dark green, lustrous above, and paler and smooth beneath. The marginal teeth are rounded and somewhat hooked. The teeth near the base of the leaf are smaller than those toward the pointed tip.
- The leaves of Populus deltoides have two glands near the stem.
- The stems of many kinds of poplars are flattened near the leaf and look as though they've been pinched. That's why the leaves of the Cottonwood and its relatives are usually in motion. Even a slight breeze can make them flutter.
- Flowering and Fruiting- Eastern cotton wood is dioecious, which means that male flowers and female flowers are produced on different trees. Only the female flowers will develop into fruit. The floral buds develop in the summer and open during spring of the following year. Flowering occurs from February to April before leaves appear. Male flowers are only 8 to 13 cm (3 to 5 in) long. They have 40 to 60 stamens and are reddish in color and more conspicuous than the female flowers. Female flowers elongate to 15 to 30 cm (6 to 12 in). Males tend to flower a few days earlier than females. Trees as young as 4 to 5 years old have flowered.
- Seed Production and Dissemination- Seed production starts when the trees are 5 to 10 years old, increasing rapidly in amount as the trees become older and larger. Cottonwood trees usually have good seed crops.
- Seed dispersal follows flowering by about 2 months in southern populations and a somewhat shorter period in the North. Seed dispersal occurs from May through mid-July in the South and June through mid-July in the North. Seeds may be carried several hundred feet by the wind, aided by the "cotton" attached to the seed. Seeds falling in water may be carried a long distance from the parent tree before being left on silt deposits.
- Seedling Development- Unless floating on or immersed in water, cottonwood seeds must reach a favorable seedbed and germinate very soon after falling. Germination of fresh seeds may exceed 90 percent. Seedlings are delicate for the first few weeks. Rains, very hot sunshine, and damping-off fungi kill many of them. Very moist, exposed mineral soils, such as fresh silt deposits, are required. Germination is epigeal. Growth rate of the fragile seedlings is slow for the first 3 weeks but may be very rapid after that. Full sunlight for a substantial part of each day is required after the first few weeks.
- 1 - Silvics Manual Volume 2 - Eastern Cottonwood http://www.na.fs.fed.us/pubs/silvics_manual/Volume_2/populus/deltoides.htm
- Unlike mose of the photos on this site, the ones on this page were not taken at Morton Arboretum.
- Last photo on page, male flowers of Populus deltoides is courtesy of Al Schneider @ USDA-NRCS PLANTS Database
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