Southwest Plant of the Month – Rio Grande Cottonwood – Populus deltoides subsp. wislizenii

General Information

Physical Description: Fast growing, very large shade tree with an open, broad-spreading crown from a massive trunk and limbs with deeply furrowed, corky gray bark. Waxy, light green, spade-shaped leaves turn bright golden yellow in fall. Male trees have dark red catkins in late spring. females produce capsules full of cottony seeds that drift upon the breeze.

Care and Maintenance: High maintenance tree outside of its natural habitat. Leaf and twig litter. Allergenic pollen and flammable accumulations of cottony seed fluff. Susceptible to cotton root rot, iron chlorosis, mistletoe, wetwood, fall webworm, leaf miners, leaf and stem galls, wood borers, leaf rust, leaf beetles, dothichiza, phomopsis, septoria cankers and probably the common cold. The wood is weak and brittle and sudden limb breakage from winds or other stress can severely damage any nearby structures.

Gardener’s Notes: Although majestic in stature and beautiful in golden fall foliage, Cottonwoods need deep rich soils and frequent deep irrigation to stay healthy. Native to the flood plains of the Rio Grande including El Paso and other riparian areas of the northern Chihuahuan Desert and extends into Utah and Colorado. See also entry for P. fremontii (Arizona cottonwood), which replaces this one to the south and west. Not a tree for the average residential landscape.

Plant information from Southwest Yard & Garden Plant Advisor.