Southwest Colorado Wildflowers, Populus deltoides 2

Populus deltoides subspecies wislizeni (Cottonwood, Rio Grand Cottonwood, Alamo Cottonwood)
Salicaceae (Willow Family)

Semi-desert, foothills. Canyons, washes, streamsides. Spring.
McElmo Canyon, April 16, 2005.

Cottonwoods are dioecious; they have male parts on one tree, female parts on another. This tree has male pollen chains elongating before leaves emerge.

Populus deltoides subspecies wislizeni (Cottonwood, Rio Grand Cottonwood, Alamo Cottonwood)
Salicaceae (Willow Family)

Semi-desert, foothills. Canyons, washes, streamsides. Spring.
McElmo Canyon, April 21, 2008.

The male reproductive parts are encased in tiny red spheres in tight clusters which in turn are in long chains. The chains open from the bottom upward as filaments and stamens push through the red coverings. The tiny black protrusions in the bottom third of the photograph are the stamens which are covered with even more minute pollen grains.

Populus deltoides subspecies fremonti (Fremont's Cottonwood)
Salicaceae (Willow Family)

Semi-desert, foothills. Canyons, washes, streamsides. Spring.
Petrified Forest National Park, Arizona, March 25, 2007.

Before leaves appear, sticky, protective bud covers (bottom of photo) unfold exposing numerous fringed, white, flower bracts that curl back to expose the gelatinous-looking stigmas above the ovary (not visible). A circular green platter-shaped appendage subtends the stigma and ovary.

John Fremont collected the type specimen of this tree in northern California in 1846 and it was named and described by Sereno Watson in 1875.

Populus deltoides subspecies wislizeni (Cottonwood, Rio Grand Cottonwood, Alamo Cottonwood)
Salicaceae (Willow Family)

Semi-desert, foothills. Canyons, washes, streamsides. Spring.
McPhee Reservoir, Dolores, April 6, 2007.

Female trees ripen their seed pods (the shiny green orbs) in long chains.

Populus deltoides subspecies wislizeni (Cottonwood, Rio Grand Cottonwood, Alamo Cottonwood)
Salicaceae (Willow Family)

Semi-desert, foothills. Canyons, washes, streamsides. Spring.
Hunter Canyon, Utah, May 2, 2005.

Eventually female trees appear to have grape clusters.

Populus deltoides subspecies wislizeni (Cottonwood, Rio Grand Cottonwood, Alamo Cottonwood)
Salicaceae (Willow Family)

Semi-desert, foothills. Canyons, washes, streamsides. Spring.
Hunter Canyon, Utah, May 2, 2005.

The individual spheres of seeds explode into a cottony mass, merge with the other explosions on the same chain, and then winds tear them apart and the white fluff fills the air.