- Division: Tracheophyta
- Class: Liliopsida (monocotyledons)
- Order: Arecales
- Family: Arecaceae
- Genus: Washingtonia
- Species: filifera
Native to deserts of the southwestern US and Baja California, Mexico, California fan palms cluster around year-round sources of water: streams, springs, and seeps. They are the only palm native to the western US, where they tolerate hot summer and freezing winter temperatures. They provide shade and shelter, habitat for wildlife including canyon tree frogs Hyla arenicolor, Pacific chorus frogs Pseudacris regilla, Baja ratsnakes Bogertophis rosaliae, western yellow bats Lasiurus xanthinus, and many birds. Their fruits ripen and drop in winter, providing food for coyotes Canis latrans, which are important seed disseminators for these palms.
The sturdy trunk of this palm rises to support the roundish crown of tough, fan-shaped fronds that give the California fan palm its name. Sharply toothed at the base, fronds can be 5 to 10 feet (1.5 to 3 meters) long, with many thread-like fibers unraveling from the leaf segment margins. Dead fronds hang from the tree, forming a thick skirt. White or yellow flowers bloom in early spring. California fan palms may reach 60 feet (18 meters) tall and 10 to 20 feet (3 to 6 meters) wide at the crown