Pignut.—One of the [Hickories], q. v.
Pine.—Nearly forty species of pine are found in the United States. They have high ornamental qualities and are used extensively in nearly every part of the country. Except on the great plains, one or more species are to be found. The different species grow from mere dwarfs to immense trees. For park purposes the white pine (Pinus strobus), an imported Scotch pine, an imported Norway pine, and the dwarf mugho have been very popular. (The sugar pine (P. lambertiana) grows in the high regions of California, is a fine tree and has cones 16 to 18 inches long).
Plane Tree.—See [Sycamore].
Plum.—Is used in thickets for screening and for its flowers and fruit. Pissard’s plum has been largely used for ornamental planting. The American plum (Prunus americana) works well in a general composition and is very thrifty.
Poplar.—The aspen, cottonwood, and balm of Gilead, have already been mentioned, one more needs attention, whitewood or tulip tree (Liriodendron tulipifera), found native in the eastern part of the United States. It is the tree from which the whitewood of commerce is mostly obtained. It grows to a height of 90 to 150 feet, and to a diameter of 6 to 12 feet, with a corresponding wide spread. It has been cut out until it is not particularly common any more. On account of the wood being soft, without knots, and free from season checks, the logs were utilized by the Indians for “dugout” boats. Hough states some were large enough to carry twenty or thirty persons. This, one of the most useful of American deciduous trees, deserves more liberal planting.
Quercus.—See [Oak].
Redwood.—These trees are native to California. There are two species—the mammoth trees (Sequoia washingtonia) of which a comparatively few large specimens remain, and the common redwood (S. sempervirens) which is now being rapidly cleared off by lumber companies. “Big or mammoth trees have been measured up to 320 feet in height and 35 feet in diameter” (Snow). These trees on account of the thick bark, on the large trees some 2 feet, resist fires very well. This is shown by ring counting and investigations on a fallen tree by Professor Dudley.[218] This tree dated back to 271 years before the Christian Era and showed that fires had occurred during the years A.D. 245, 1441, 1580, and 1797. The last fire charred a space 30 feet high and 18 feet broad, but full recovery had been made. The tree grows rapidly. Snow states that trees have been known to develop a height of 80 feet and a diameter of 16 inches in thirty years. In the Mariposa grove, at least partially under U.S. Forest Reserve, the roads wind about through the great natural avenues formed by these trees. On account of the great commercial value of redwood the trees might, in places where they will grow, be utilized for road planting to encourage their growth by others, and assist the government in its long-time forest plans.
Sassafras.—Native to the eastern part of the country is a good looking tree of small size, rising to a height of 30 to 50 feet with a spread one-third as great. It has the characteristic sassafras odor, the bark of the roots being used for medicine. Will mass well. The leaves being some lobed and some not lobed lend a pleasing variety. Is best in naturalistic planting.
Sequoia.—See [Redwood].
Shagbark.—See [Hickory].