Gambel Oak is a tree of distinctive leaves and variable growth. It occurs
from shrub size to a large 50 foot tree with a 2½ foot diameter trunk. Trees 10
to 25 feet tall are most common at the South Rim. The Gambel oak grows most
often in thickets of a dozen or more. These are usually clones that grew up from
a single root system, often after a fire. Gambel oak bark is gray, fissured and
hard. The trees in this photo are in fall colors: yellow, never red.
Gambel oak is Arizona's only oak with oakish leaves: 2 to 6 inches long and deeply lobed like an eastern oak. A deciduous tree, its leaves come out rather late in spring, often in May, and they turn yellow and drop off in October. So the growing season at the South Rim is only about five months.
Deer browse the leaves and one-inch acorns. Other mammals and also
birds enjoy the relatively sweet acorns. Native peoples utilized this rich
source of protein, eating acorns raw or ground into flour, often after soaking
overnight. Indians also used the hard, flexible wood for implements and
Each acorn woodpecker clan assiduously and vociferously guards its acorn granary tree (often a nearby conifer snag) against interloping clans.
While most South Rim Gambel Oaks are small, this winter photo shows that the tree can grow large here.