Perhaps the only native palm trees in Arizona are tucked away in narrow, rugged canyons on the Kofa National Wildlife Refuge. The Palm Canyon Trail is a short hike and takes you near a stand of these unique plants, called California fan palms, Washingtonia filifera.
California fan palms are probably descendants of palms that grew in this region during the last periods of North American glaciation. Some botanists theorize that the trees gradually spread into these canyons and other protected niches as the climate warmed to desert conditions. Other researchers have suggested that the trees may have been spread from other palm groves by birds or coyotes carrying seeds in their digestive tracts.
Since palm trees do not produce annual growth rings like shade trees, it is very difficult to say how old the trees might be. In Palm Canyon, the palm trees are able to survive the in the narrow side canyons where direct sunlight is limited but some moisture is available. The probability of these trees surviving very long is directly dependent on the microclimate in that protected canyon.
The most prominent trail leads to a small sign on a slightly elevated area near the middle of the canyon. By looking upward in the narrow, north trending side canyon, you will see the palms clearly. For a short time at midday, the trees are well-lighted for photos. The rest of the time the trees are shaded.
In 1986, 42 trees were counted in the main grove. About half of those are adult size, with a trunk of 20 feet or more. Some smaller trees are becoming established at the base of the larger trees.
As the fronds, or large leaves, on the California fan palm die, they fold downward around the trunk of the tree and form a "petticoat." The petticoat on younger trees extends from the ground to the crest. For some reason, the fronds on the older trees in Palm Canyon do not form a lengthy petticoat. The fronds tend to self-prune, that is they fall to the ground beneath the tree where they decompose. The decaying fronds form the growing bed for new trees.
As you follow the trail into the canyon, you will pass several species of plants unfamiliar to many visitors. The palo verde, a small tree with bright green branches and stems, rarely has leaves and grows in the washes in the area. The plant's branches and twigs have enough chlorophyll to produce all the food the tree requires. Ironwood, a gray-green tree with small leaves is also present in the wash where the trail crosses. Its leafy stems are covered with thorns. Near the upper end of the trail, you will notice numerous small bushes with "holly-like" leaves. This Kofa Mountain barberry is not common on the refuge and is found only in the southwest corner of Arizona.