by Allen Zufelt, Native Plants Class 2002
Common names: Fremont cottonwood, Arizona cottonwood, Alamo cottonwood
Family: Salicaceae
Synonymy: Populus fremontii var. mesetae (Eckenwalder), Populus fremontii var. pubescens (Sarg.)
Etymology: The epithet fremontii refers to the botanist Fremont who cataloged this plant.

Identification
Growth form: Riparian tree. Mature trees ranging from 19.7 to 112 feet.
Roots:
Stem: Stem on young and immature trees are smooth. Mature trees becoming deeply furrowed. Mature trees DBH range from 19.7 inches to 12.8 feet.[8]
Leaves: Leaves are simple, alternate, and deciduous. L light green to yellow in fall. Crown becoming cylindrical or broad and rounded. [7, 6, 5]
Inflorescence/flowers: Produce catkins. Male catkins range from 1.25 to 3.25 inches. Female catkins range from 4 to 5 inches.[9]
Similar species: Populus angustifolia, Populus trichocarpa, P. fremontii will hybridize with P. angustifolia to produce P. hinkleyana [8] and with P. tricocarpa to produce P. parryi.

Ecology
Life history: Short lived as compared to other trees, around 130 year lifespan.
Native/introduced: Native[5].
Photosynthetic pathway:
Phenology: This cottonwood is an obligate sexual producer, wind disseminated seeds in the spring give the plant its common name. Will regenerate asexually after crown damage, or disturbance.
Distribution: Elevational distribution from 0 to 9400 ft in Arizona. Obligate riparian tree, found often in mixed stands with willows (Salix spp.).[1] Drought intolerant, growing tree roots can extend as much as half an inch per day to reach the water table.

Uses
Wildlife: These cottonwoods are very important for bird nesting habitat and cover. Fair to good forage food for deer, and other native species. Considered a valuable browse plant for livestock.[1]

References
1. Welsh, Stanley L.; Atwood, N. Duane; Goodrich, Sherel; Higgins, Larry C., eds. 1987. A Utah flora. The Great Basin Naturalist Memoir No. 9. Provo, UT: Brigham Young University. 894 p.

2. 135. Sampson, Arthur W.; Jespersen, Beryl S. 1963. California range brushlands and browse plants. Berkeley, CA: University of California, Division of Agricultural Sciences, California Agricultural Experiment Station, Extension Service. 162 p. [3240] 148. Szaro, Robert C. 1989. Riparian forest and scrubland community types of Arizona and New Mexico. Desert Plants. 9(3- 4): 70-138.

3. Powell, A. Michael. 1988. Trees & shrubs of Trans-Pecos Texas including Big Bend and Guadalupe Mountains National Parks. Big Bend National Park, TX: Big Bend Natural History Association. 536 p.

4. Kearney, Thomas H.; Peebles, Robert H.; Howell, John Thomas; McClintock, Elizabeth. 1960. Arizona flora. 2d ed. Berkeley, CA: University of California Press. 1085 p.]

5. Eckenwalder, James E. 1992. Salicaceae: Willow family. Part one: Populus. In: A new flora for Arizona in preparation. In: Journal of the Arizona-Nevada Academy of Science. 26(1): 29-33.

6. Eckenwalder, James E. 1977. North American cottonwoods (Populus, Salicaceae) of sections Abaso and Aigeiros. Journal of the Arnold Arboretum. 58(3): 193-208.