The most common pinyon pine in California is the single leaf pinyon, P. monophylla . The desert mountains of Utah, Idaho, Colorado, Arizona and Baja California are also home to this tree, growing between the elevations of 2,000 to 10,000 feet. The single leaf pinyon is easily recognized in the field by its shape and leaves. Bark on older trees has narrow flat ridges, with thin, close, dark brown, sometimes reddish brown scales. Young tree bark is smooth and dull gray.
Leaves are mostly single, with a small proportion of two-needled fascicles.
This leaf character is due to the abortion of one of the original two-needle primordia at a very early stage. The pale green leaves are three to five centimeters long, with dark green lines. They are stiff, prickly and curved toward the branch with deciduous sheaths. The pinyon pine is noteworthy for being the only pine with single needles that end in a spike. Reproductive maturity comes at a relatively old age, about twenty-five years.