GRAY PINE (_Pinus sabiniana_), called also Digger pine because the Digger Indians formerly collected the seeds, which are as large as peanuts, to help eke out a living, is confined to California, and grows in a belt on the foothills surrounding the San Joaquin and Sacramento valleys. Its cones are large and armed with hooked spines. When green, the largest cones weigh three or four pounds. Leaves are from eight to twelve inches long, in clusters of two and three, and fall the third and fourth years. The wood is remarkable for the quickness of its decay in damp situations. It lasts one or two years as fence posts. A mature gray pine is from fifty to seventy feet high, and eighteen to thirty inches in diameter. Some trees are much larger. It is of considerable importance, but is not in the same class as western yellow and sugar pine. The wood is light, soft, rather strong, brittle. The annual rings are generally wide, indicating rapid growth. Very old gray pines are not known. An age of 185 years seems to be the highest on record. The wood is resinous, and it has helped in a small way to supply the Pacific coast markets with high-grade turpentine, distilled from roots. It yields resin when boxed like the southern longleaf pine. There are two flowing seasons. One is very early, and closes when the weather becomes hot; the other is in full current by the middle of August. It maintains life among the California foothills during the long rainless seasons, on ground so dry that semi-desert chaparral sometimes succumbs; but it is able to make the most of favorable conditions, and it grows rapidly under the slightest encouragement. The seedlings are more numerous now than formerly, which is attributed to decrease of forest fires. The tree has enemies which generally attack it in youth. Two fungi, _Peridermium harknessi_, and _Dædalia vorax_, destroy the young tree’s leader or topmost shoot, causing the development of a short trunk. The latter fungus is the same or is closely related to that which tunnels the trunk of incense cedar and produces pecky cypress.
Gray pine has been cut to some extent for lumber, but its principal uses have been as fuel and mine timbers. Many quartz mines have been located in the region where the tree grows; and the engines which pumped the shafts and raised and crushed the ore were often heated with this pine. Thousands of acres of hillsides in the vicinity of mines were stripped of it, and it went to the engine house ricks in wagons, on sleds, and on the backs of burros. In two respects it is an economical fuel for remote mines: it is light in weight, and gives more heat than an equal quantity of the oak that is associated with it.