The Coulter pine or big-cone pine, Pinus coulteri, is a native of the coastal mountains of Southern California and northern Baja California, and is present in both the Angles National Forest and the San Bernardino Mountains in San Bernardino County. Isolated groves are found as far north as the San Francisco Bay Area in Mt. Diablo State Park and Black Diamond Mines Regional Preserve. The species is named after Thomas Coulter, an Irish botanist and physician. Pinus coulteri is a substantial coniferous evergreen tree in the genus Pinus.
The Coulter pine produces the largest cone of any pine tree, ranging to over ten pounds in weight and measuring over a foot long. Although this tree has a limited range in the wild, it is a popular ornamental tree. Its wood is soft and weak, so is not used for much other than firewood by man.
Also known as the California Coulter pine, Big-cone pine, Nut pine, and Pitch pine, it is a slow growing species, reaching only 20 feet in 20 years. In optimal sites, it can grow as tall as 80 feet with a trunk diameter of 1 to 3.3 feet. Root depth is about 40 inches. These trees prefer deep, well-drained, acidic soils. Moisture requirements vary between moist and dry for the soil but it does require a considerable amount of rain annually and it has a low drought tolerance. Soils tend to be of medium texture, gravelly, or loamy. The minimum temperature for survival is 12 degrees Fahrenheit and more than 145 days of frost per year will threaten their survival. Large trees are resistant to low and moderately severe fires.
The bark is gray on young trees, becoming dark purplish-brown or black with thick, scaly, broad ridges. The trunk is vertical and branches horizontal to upcurved. The leaves are needle-like and stiff, in bundles of three, glaucous blue-green to gray-green, about 10 to 12 inches long.
The outstanding characteristic of this tree is the large, spiny cones which are 7.9 inches to 15.7 inches long, and weigh 4.4 pounds to 11 pounds when fresh. Coulter pines produce the largest cones of any pine tree species, although the slender cones of the sugar pine are longer. The large size of the cones has earned them the nickname “widowmakers” among locals, and people are advised to wear hardhats when working in Coulter pine groves. Coulter pine cones occur in whorls of 4 and stay on the tree for 5-6 years. Each cone contains many large, edible, brown seeds that are .8 inches in diameter.
The Coulter pine is closely related to the Jeffrey pine, with which it shares habitats, and the ponderosa pine, though Coulter pines tend to grow in drier environments than their cousins.
As an erect, medium-sized pine, the Coulter prefers south-facing slopes between 660 feet to 7,550 feet in elevation, and tolerates dry rocky soil. Pinus coulteri most often appears in mixed forests. The Coulter pine occurs in a number of forest plant associations, so that it will be co-dominant with the California black oak among other trees. Woodpeckers often forage on the species, peeling the bark to access insects underneath. Female Whiteheaded Woodpeckers feed almost exclusively on insects found on the lower trunks and the males eat seeds from the cones.
The life span of Coulter Pine is moderate for trees and most reach at least 100 years of age.