Rio Grande Cottonwood
Scientific name: Populus wislizeni
Alternate names: Narrowleaf, Alamo or Guerigo
Description: This is the cottonwood of desert waterholes and watercourses. A deciduous poplar of the Willow family with broad, flattened, open crown of large, widely spreading branches & trunk diameter of 2 to 5 feet. Easily propagated from cuttings, it is extensively planted in its range along irrigation ditches. Although it is a fast-growing shade tree, it is short-lived.
Bark: The heartwood of this tree is deeper brown than that of Fremont cottonwood but the sapwood is white. On older trees, the bark is thick, deeply furrowed, reddish brown. On branches or on young trees, bark is thin, smooth and gray-brown.
Leaves: Roughly triangular in shape, 2 to 2.5 inches long and 2.5 to 3 inches wide. They are shiny green with a thin yellow midrib, a coarsely toothed margin & a yellow, flattened stem that causes the leaf to shake back & forth in the wind. Leaves turn bright yellow in autumn.
Twigs: light green, stout, hairless.
Flowers: Catkins 2 to 3 1/2 inches long, reddish; male and female on separate trees in early spring.
Fruits: Multiple 1/2 inch long, egg-shaped, seed bearing capsules in a clump, hairless, light brown, maturing in spring, splitting into 3 or sometimes 4 parts with many cottony seeds.
Habitat: Wet soils along streams or near lakes in deserts, grasslands & woodlands
Range: This tree occurs along the Rio Grande from Mexico to southern Colorado and in the San Juan basin in northwest New Mexico and southwest Colorado.
Height: 40 to 80 feet
Elevation: Up to 6500 feet
Water Requirements: Moderate-High. Rio Grande cottonwood grows only on wet soil and is an indicator of permanent water and shade. In the desert, it needs weekly watering during hot weather if roots cannot tap the water table.
Wildlife: Horses gnaw the sweetish bark; beavers feed on the bark and build dams with the branches.