GRAY PINE grows only in California, encircling the central valley nearly entirely at around 1,000 feet to 3,000 feet. It often associates with blue oak (Quercus douglasii) in the hot, dry foothills, and grows in open woodlands just below the ponderosa pine belt. It is also called foothill pine and ghost pine, and was formerly called digger pine. Gray pine is drought tolerant, and can survive on 10 inches of annual rainfall. More interesting details are found in this blog post.
Gray pine is an open, sparsely foliaged pine, usually multi-trunked, and not particularly large, but can grow to 100 feet. Reports from earlier times mention that gray pine could be up to 140 feet high and 3 to 12 feet in diameter, and may have lived over 200 years. The bark is dark and thickened on mature trees, which self-prune bottom branches, a fire-avoiding strategy.
The American Conifer Society has a wonderful, descriptive page about gray pine here.
On a cycling trip in Big Sur I was surprised to find a few gray pines growing uncharacteristically almost to the Pacific Ocean.
Pinnacles National Park has some of the largest gray pines I've seen.
These three photos of gray pine show how different it can appear. Tree on the left, taken at Mt Diablo SP, exhibits very gray foliage.
Bottom left shows less divided trunk, bottom right shows typical open, sparsely foliaged, multi-divided trunk. Both are taken at Pinnacles NP.
Grayish-green needles, 8 to 12 inches long, hang loosely and occur in groups of three.
The heavy cones are 6 to 10 inches long, with sharp pointed scales, and take two years to mature. The seeds are large and nutritious. These cones are second in mass only to Coulter pine (Pinus coulteri).
Shown below is a gray pine cone on the right, shorter and wider than the Coulter pine cone on the left.