Ponderosa Pine - Pinus ponderosa

Ponderosa Pine - Pinus ponderosa
Family Pinaceae
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Ponderosa Pine Tree
This Ponderosa pine is a Morton Arboretum specimen.

Ponderosa pine, also called western yellow pine, is one of the most widely distributed pines in western North America. A major source of timber, ponderosa pine forests are also important as wildlife habitat, for recreational use, and for esthetic values.

Within its extensive range, two varieties of the species currently are recognized: Pinus ponderosa var. ponderosa (Pacific ponderosa pine) (typical) and var. scopulorum (Rocky Mountain ponderosa pine). Arizona pine (P. arizonica), sometimes classified as a variety of ponderosa pine, is presently recognized as a separate species.

Ponderosa pine wood is principally used in millwork, including windows, doors, shelving, molding, knotty-pine paneling and dimension lumber. Sap used as glue and source of turpentine oils.

Native Americans used inner bark and seed as food, sap was used as a chewing gum. Source of pyrone used as a FDA approved flavoring to bread and cakes.
Medicinal - Pinus species have been used as an antiseptic, an expectorant, a poultice to treat boils, rheumatism, backaches and other inflammations.

Ponderosa Pine forests are usually selectively harvested rather than clear cut. This method of logging removes only the mature trees and leaves the other trees to re-seed and mature. Selective harvesting often makes it difficult to identify a recently logged stand.

Ponderosa Pine is one of the Western pine species that includes Idaho White Pine (pinus monticola), Sugar Pine (pinus lambertiana) and Lodgepole Pine (pinus contorta). The Western pines are distinct from the Southern Yellow pines which are denser and pitchier, with widely different characteristics and uses. (1)

Ponderosa Pine Needles

Ponderosa Pine is one of America's abundant tree species, covering approximately 27 million acres of land. Stands can be found from Canada to Mexico and from the Pacific Coast eastward to the Black Hills of South Dakota. Its growth range covers an area encompassing more than 35 percent of the total acreage of the U.S. (2)

Ponderosa Pine trees average 100' to 160' in height, with some exceeding 180'. The trees range from 2-4' in diameter, with the rate of growth depending upon titleitude, soil, temperature and rainfall.

Mature Ponderosa Pines can be easily identified by their distinctive orange-brown bark which is arranged in large plates. The dark yellow-green needles are 5-10" long and grow in clusters of three. The cones, similar in color to the bark, are 3-6" long and 2-4" in diameter. Seeds are 5/16-3/8" long with a 3/4-1" wing.

Ponderosa Pine is well suited for remanufacturing which requires clear, splinter-free wood, with a minimum of knots, resin and other unwanted characteristics. The large trees include substantial volumes of virtually clear sapwood with relatively few, widely-spaced knots. Shop and Factory lumber is graded to yield standard cuttings of clear material suitable for fabrication. Such wood is selected to be almost completely free from pitch and resin pockets, has an even grain and is dimensionally stable. Ponderosa also ranks moderately high for ease of gluing and is used for all types of products where glued-up construction is required.

The species is prized for moulding and for doors, windows, frames and drawers where durability under movement is essential. It has the ability to withstand scuffs, shocks and jars without spliting, which makes it the premier wood for these and other applications such as sashes, jambs, shutters, screens, columns, stairwork and fascia. Pine paneling is often associated with Early American decor in kitchens, family rooms, dens and bedrooms. However, new finishing techniques and patterns make it appropriate for contemporary or traditional settings.

Industrial uses for Ponderosa Pine include pallets, concrete forms, crates and boxes, dunnage, hives, partitions and foundry patterns. It is also used for a wide variety of wood packaging and novelty items such as boats, wagons, toys, window shade slats, rat and mouse traps. (2)

Ponderosa Pine Crown
Ponderosa pine's open, spreading crown makes for moderate, dappled shade.

The range of ponderosa pine extends from southern Canada into Mexico, and from the Plains States of Nebraska and Oklahoma to the Pacific Coast. Pacific ponderosa pine (var. ponderosa) ranges from latitude 52° N. in the Fraser River drainage of southern British Columbia, south through the mountains of Washington, Oregon, and California, to latitude 33° N. near San Diego. In the northeast part of its range it extends east of the Continental Divide to longitude 110° W. in Montana, and south to the Snake River Plain, in Idaho. Rocky Mountain ponderosa pine (var. scopulorum) extends east of the Continental Divide from latitude 48° N. in north-central Montana, southeasterly into North and South Dakota, eastern Wyoming, and as far east as north-central Nebraska.

Within this area, ponderosa pine grows on the discontinuous mountains, plateaus, canyons, and breaks of the plains, with the most extensive stands found in the Black Hills of South Dakota and Wyoming. South of Wyoming, Rocky Mountain ponderosa pine extends south on both sides of the Continental Divide, west to Arizona, and the eastern edge of the Great Basin in Nevada, east to Texas west of the Pecos River, New Mexico, extreme northwestern Oklahoma, Colorado, and northern Mexico.

Within this wide range, ponderosa pine is absent from a large area that includes southwestern Montana, western Wyoming, southern Idaho, and part of the Great Basin. A possible explanation for the absence is that the distribution of rainfall during the summer months prevents seedling establishment except at higher elevations, where the species has little tolerance for the shorter growing season. Arizona pine (var. arizonica) is found primarily in the mountains of extreme southwestern New Mexico, southeastern Arizona, and northern Mexico. (1)

Ponderosa pine seeds are consumed by a great many birds and small mammals such as mice, chipmunks, and tree squirrels. In years of low cone production, the potential seed crop may be severely reduced. Squirrels clip many of the cone bearing twigs, destroying flowers and conelets. Because of ponderosa pine's intolerance of shade, it tends to grow in even-aged stands and is usually managed by that method. Uneven-aged stands might appear common throughout the drier portion of its range but are in reality a mosaic of even-aged groups. Ponderosa pines lose vigor in dense stands.

Damaging Agents- Rabbits and hares injure or kill many seedlings, and pocket gophers are especially destructive. In areas where pocket gopher populations are high all seedlings and many saplings may be destroyed. Squirrels and porcupines attack sapling and pole-size trees and, although rarely killing them, deform the stems on which they feed. Repeated browsing by deer has stunted seedlings for 50 years or more. In the absence of regulation, sheep and cattle have damaged reproduction by trampling, bedding, and occasional browsing.

At least 108 species of insects attack P. ponderosa var. ponderosa, and 59 species attack P. ponderosa var. scopulorum. The most damaging of the tree-killing insects are several species of Dendroctonus. Trees die from the combined effects of a blue stain fungus transmitted by the beetle and extensive larval consumption of the phloem. The western pine beetle (D. brevicomis) is a common cause of mortality in overmature, decadent trees within the range of ponderosa pine from Baja California, north into Oregon, Washington, western Canada, Idaho, and western Montana. During epidemics, however, apparently healthy, vigorous trees are also killed. During the drought years of the 1930's, losses from western pine beetle in the Pacific Northwest were so heavy that many foresters feared for the pine stands' continued existence. The mountain pine beetle (D. ponderosae) is the most destructive and aggressive enemy in the central and southern Rocky Mountains.

During the 1894-1908 outbreak in the Black Hills of South Dakota, this insect killed between 5.7 and 11 million m³ (1 and 2 billion/fbm) of ponderosa pine. Tree killing by D. ponderosae has increased with the conversion of old-growth to young-growth stands in the Pacific Northwest. High stand density is believed to reduce vigor of some of the larger trees in a stand and, therefore, is an underlying factor in the occurrence of bark beetle outbreaks. D. adjunctus, D. approximatus, and D. valens are other species of the genus that often kill ponderosa pines.

Among bark beetles, Ips species are second in destructiveness only to Dendroctonus. Ips are present naturally in all stands, where they usually breed in slash. In abundant slash from forestry activities, Ips can kill vigorous ponderosa pine up to 66 cm (26 in) in d.b.h. when populations reach explosive levels. Eleven species of Ips have been found attacking ponderosa pine. Of these, I. latidens, I. emarginatus, I. pini, I. lecontei, and I. paraconfusus have the most impact.

Several insects mine buds and shoots, primarily of young trees. although seldom killed, trees are retarded in growth when infestations are severe. Pine tip moths (Rhyacionia spp.) and the gouty pitch midge (Cecidomyia piniinopis) kill the buds and shoots they mine. A more insidious pest, until recently overlooked and overrated, is the western pineshoot borer (Eucosma sonomana). Larvae of this species bore within the pith of the terminal shoot, stunting but seldom killing them. Shoots that are potentially more robust are more likely to be infested than are weaker shoots. Accordingly, direct comparisons of infested vs. uninfested shoot lengths will underestimate actual growth loss. Each terminal shoot infested by a larva that developed to maturity was reduced in length that year by more than 25 percent in one study. The pine reproduction weevil (Cylindrocopturus eatoni), a native of California and, presumably, Oregon, can be a threat to slowgrowing plantations. Its impact has declined, however, with the improvement in planting stock and control of competing vegetation.

Defoliating insects, such as the pine butterfly (Neophasia menapia) and the pandora moth (Coloradia pandora), periodically cause damage over extensive areas. The pine needle sheathminer (Zelleria haimbachi) can be locally severe in young stands. Dwarf mistletoe (Arceuthobium vaginatum ssp. vaginatum in the Southwest, and A. campylopodium in California and the Northwest) is ponderosa pine's most widespread disease, absent only in the Black Hills. It seems to be particularly devastating in the Southwest, where it infects trees on about onethird of the commercial acreage. At Fort Valley Experimental Forest in northern Arizona, dwarf mistletoe has caused up to 36 percent of the mortality. On trees not killed, the parasite is responsible for a significant loss in growth, primarily in height, and is reported to reduce seed viability as much as 20 percent. In the Northwest, A. campylopodium has little effect on vigorous, young trees because height growth will usually exceed its upward spread, relegating the parasite to the lower crown.

Several diseases attack ponderosa pine roots. Black stain root disease, Leptographium (syn. Verticicladiella) wageneri, causes a diffuse dark staining of the root wood and kills roots. Heterobasidion annosum causes an insidious lethal root disease that is spread by airborne spores to the surfaces of freshly-cut stumps. It and L. wageneri kill trees of all ages and usually result in group mortality that is sometimes mistaken for the work of bark beetles, which are frequently secondary invaders. Armillaria sp., previously considered weak root and butt decayers, are causing increased mortality in young plantations and thinned stands where the disease can build up in dead root systems. Active infection centers of L. wageneri and H. annosum spread about 1 m (3 ft) per year. The rate is usually less for Armillaria sp. The most damaging heart rot in the southern Rocky Mountains and the Black Hills is western red rot caused by Dichomitus squalens. It is a major cause of loss of sound wood in commercial stands. Because ponderosa pines older than 100 years have substantially greater defect, shorter rotation ages should eliminate much of the heart rot. Phellinus pini is the major heart rot in the Pacific Coast States.

Air pollution is an increasing and vexing source of foliar damage to ponderosa pine. Ozone is the major plant-damaging constituent of photochemical oxidant air pollution. Ozone becomes concentrated enough to cause damage near the border of air basins and in the predominant summer downwind direction from heavily populated areas. Because ponderosa pine, especially var. ponderosa, is susceptible, and because it grows near areas heavily polluted, ozone damage can be great. Typical injury is a chlorotic mottling accompanied by premature abscission of old needles. Moderately or severely injured trees are attacked more frequently by bark beetles and Heterobasidion annosum root disease.

In ponderosa pine forests, timber production, livestock grazing, and recreation are the principal land uses. Ponderosa pine forests are found at low elevations offering year-round recreation, and they frequently border forest highways where esthetic values are high. They provide habitats for various wildlife species. Abert's and Kaibab squirrels usually live in the ponderosa pine forests (55). Snags in the mature pine forest provide a large number of species with nesting and roosting sites. Big game, such as deer and elk, also use the pine forests for food and shelter.

Hybrids
Natural crosses of ponderosa pine with Jeffrey pine have been observed in California where their ranges overlap, but they are rare. Where the two species grow in the same stand, different flowering times and other reproductive barriers restrict crossing. Ponderosa pine crosses with Pinus montezumae and P. arizonica, and rarely with P. engelmannii. Introgressive hybridization has been observed with P. washoensis. In addition to the natural hybrids, artificial crosses have been obtained with a number of other hard pine species, including P. durangensis. (1)

References:
1. USDA United States Forest Service Silvics Manual Pinus ponderosa
2. Western Wood Products Association, Ponderosa Pine

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