Bishop pine (Pinus muricata) is a coniferous evergreen tree that grows mostly in California, including several offshore Channel Islands, and a few locations in Baja California, Mexico. It is always on or near the coast, where it can withstand drought and salt spray. It has a distinctive appearance with dark gray bark, green to blue-green needles in pairs, and prickly ovoid cones that persist on the tree for many years. Bishop pine is also known as obispo pine, pricklecone pine, dwarf marine pine, umbrella pine, bull pine, pitch pine, or Santa Cruz Island pine.

Bishop pine can grow to a height of 15 to 26 meters (49 to 85 feet), with a trunk diameter of up to 1.2 meters (3.9 feet). The species is often smaller, stunted and twisted in coastal exposures. The needles are 8 to 16 cm (3 to 6.5 inches) long and slightly twisted. The cones are strongly reflexed down the branch, 5 to 10 cm (2 to 3.9 inches) long; the scales are stiff, thin on the side of the cone facing the stem, but greatly thickened on the side facing away and with a stout 5 to 12 mm (0.2 to 0.47 inch) spine; both features adaptive to minimize squirrel predation and fire damage to the cones. The cones remain unopened for many years until fire or strong heat causes them to open and release the seeds.

There are two forms of bishop pine: a southern form with bright green needles and a northern form with dark blue-green needles. The resin composition also differs. The dividing line between the two is very sharp, five miles south of the boundary between Mendocino County and Sonoma County, California. Experimental attempts to hybridize the two forms have consistently failed, indicating that their taxonomic relationship may be more distant than the very small differences in appearance would suggest.

Bishop pine is found with several oak and cypress associates within the California Coast Ranges. It prefers already disturbed, unvegetated areas where it probably faces less competition from oaks and shrubs. It is also tolerant of serpentine soils and can form pure stands on such sites. Bishop pine is an important habitat for many birds and mammals, such as woodpeckers, nuthatches, squirrels, chipmunks, deer, and bears.

Bishop pine has been used for various purposes by Native Americans and settlers, such as fuelwood, fence posts, railroad ties, pulpwood, resin extraction, and Christmas trees. It is also planted as an ornamental tree in gardens and parks, especially in coastal areas where it can provide windbreaks and erosion control. Bishop pine is relatively easy to grow from seed or cuttings, but requires full sun and well-drained soil. It is hardy to USDA zone 7.

If you are looking for a rare and prickly coastal conifer for your landscape or garden, bishop pine may be a good choice. It has a unique appearance and ecological value that will make it stand out among other pines.

Sources:

• Pinus muricata – Wikipedia
• Pinus muricata / Bishop pine – American Conifer Society
• Pinus muricata | Bishop pine Conifers/RHS Gardening