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Environmental Studies

Pinus strobus

  • Eastern white pine (Pinus strobus), also called northern white pine, is one of the most valuable trees in eastern North America. Before the arrival of white men, virgin stands contained an estimated 3.4 billion m³ (600 billion fbm) of lumber. By the late 1800’s most of those vast stands had been logged. Because it is among the more rapid growing  northern forest conifers, it is an excellent tree for reforestation projects, landscaping, and Christmas trees and has the distinction of having been one of the more widely planted American trees.

    This tree is known to the Native American Haudenosaunee (Iroquois nation) as the Tree of Peace. It is also known as the Weymouth pine in the United Kingdom, named after George Weymouth who brought it to England in 1620.

    Physical characteristics

     

    Leaf: Evergreen needles, 3 to 5 inches long, with five, slender, flexible needles per fascicle; fascicle sheath deciduous, needles appear blue-green because of 3 or more glaucous lines of stomata.

    Flower | Seeds: Species is monoecious; males cylindrical, yellow, in clusters near branch tips; females light green, tinged in red, at ends of branches.

    Fruit: Cones are 4 to 7 inches long, cylindrical, with thick, rounded cone scales, very resinous, borne on a long stalk and maturing in late summer.

    Twig: Slender, gray-green to orange-brown in color; buds long, ovoid, reddish brown.

    Bark: On young trees, thin, smooth and gray-green with some lighter spotty patches; later becoming thick, reddish brown to gray-brown with prominent finely scaly, rounded, long ridges and darker furrows.

    Form: A large tree with a very straight trunk often reaching well over 100 feet in height. The crown is conical when young, later developing wispy, horizontal, upturning branches.

    Needles: soft, flexible, blue-green; 2”–4” long, 3-sided, in bundles of five. Evergreen.

    Buds: heavily resinous and sticky, aromatic.

    Cones slender and thornless, 3”–10” long and tapering; each scale usually bears two winged seeds as do all native pines.

    Roots: wide spreading and moderately deep, without a distinct taproot.

    Height of mature trees in nature 80’–110’; largest eastern conifer.

    Spread: 20’-40’.

    Ages: exceeding 400 years are possible; commonly reaches 200 years of age and may exceed 450.

     

    Ecological characteristics

    Photo by Julia Giza

    Distribution and Ecology

    Pinus strobus can be found in Canada: Newfoundland, Nova Scotia, New Brunswick, Prince Edward Island, Québec, Ontario, and Manitoba; France: St. Pierre and Miquelon; and USA: All states from Minnesota, Iowa, Illinois, Kentucky, Tennessee and Georgia to the Atlantic Ocean (excepting Florida); the variety in Mexico and Guatemala.  Found at sea level in the North, and up to 1500 m in the South. Prefers well-drained soils and a cool, humid climate. Forms mixed stands with Tsuga canadensis, Quercus sp., or Fraxinus americana.

    Climate

    The climate over the range of white pine is cool and humid. The distribution of white pine coincides reasonably with that part of eastern North America where the July temperature averages between 18° and 23°C (65° and 74° F).

    Annual precipitation ranges from about 510 mm (20 in) in northern      Minnesota to about 2030 mm (80 in) in northwestern Georgia. In the area surrounding the Great Lakes, about two-thirds of the precipitation occurs during the warm season, April to September. Elsewhere, half of the precipitation occurs during the warm season. The length of the growing season ranges from 90 to 180 days.

    Throughout the range of white pine, precipitation is about 1 to 1.5 times the evaporation from shaded free water surfaces. Annual potential evaporation- transpiration is between 430 and 710 mm. (17 and 28 in), of which 56 to 68 percent occurs in the warm season. There is a moisture surplus in all seasons.

    Average depth of frost penetration ranges from about 25 cm (10 in) in the southern Appalachians to more than 178 cm (70 in) in parts of central and northern Minnesota. Average annual snowfall ranges from 13 cm (5 in) in northern Georgia to more than 254 cm (100 in) in New England and southern Canada.

    Soils

    The major soil orders found in the white pine range are Inceptisols, Ultisols, Spodosols, Entisols, and Alfisols. In New England the important subgroups are excessively drained or somewhat excessively drained sandy deposits or stratified sand and gravel deposits. Most of the parent materials are glaciofluvial deposits-subgroups Typic Udorthents, Typic Haplorthods, and Typic Udipsamments; glacial tills-subgroups Lithic Dystrochrepts and Lithic Haplorthods; or weathered igneous rocks (loose crystalline fragments mainly from weathered Conway granite)-subgroup Lithic Haplorthods.

    White pine grows on nearly all the soils within its range, but generally competes best on well drained sandy soils of low to medium site quality. These soils permit fair growth of white pine but not hardwoods. On these sandy sites, white pine regenerates naturally, competes easily, and can be managed most effectively and economically. On medium-textured soils (sandy loams), it will out produce most other native commercial species in both volume and value. White pine also grows on fine sandy loams and silt-loam soils with either good or impeded drainage when there is no hardwood competition during the establishment period-as on old fields and pastures, bums, and blow downs. It has been found on clay soils and on poorly drained or very poorly drained soils with surface mounds. It can be very productive on these sites but usually occurs only as individual trees or in small groups. This pine should not be planted in heavy clay soils. Poorly drained bottom land sites and upland depressions are also poor choices for planting.

    Races and Hybrids

    Eastern white pine is represented in the United States by the typical variety, Pinus strobus var. strobus. Chiapas white pine, P. strobus var. chiapensis, is native in the mountains of southern Mexico and Guatemala. Four horticultural varieties have been recognized in Connecticut.

    Eastern white pine crosses readily with western white pine (Pinus monticola), Balkan pine (P. peuce), blue pine (P. griffithii), and Japanese white pine (P. parviflora). It can also be crossed with limber pine (P. flexilis) and Mexican white pine (P. ayacahuite). The cross P. strobus x griffithii ismore vigorous than P. strobus in Northern Ohio and more winter hardy than P. griffithii.

     

     

     Importance to the ecosystem

    Although the genus Pinus is used by wildlife for food and cover, few specific observations of eastern white pine have been noted. Some species of songbirds that consume seeds of white pine are the yellow-bellied sapsucker, black-capped chickadee, white-breasted nuthatch, pine warbler, pine grosbeak, and the red crossbill. Some mammals that eat seeds, bark, and foliage of white pine are beaver, snowshoe hares, New England cottontails, porcupine, red and gray squirrels, mice, and white-tailed deer.

    White pines are useful in urban plantings. Trees grown from seeds obtained in Prince Edward Island, Nova Scotia, or in adjacent regions of New Brunswick, Maine, and New Hampshire may be more suitable than trees obtained from other regions. They usually have more compact crowns and are more resistant to snow break; they grow more slowly, have darker blue-green color, and seem to be more resistant to air pollutants than trees from other origins.

    White pine has been used extensively for stabilizing strip-mine spoils. In the anthracite region of Pennsylvania, white pine survived well on spoils that fell within the pH range 5.1 to 6.5, and growth was better on lower slopes of the spoils than on upper slopes. On bituminous spoils in West Virginia, white pine survived best on spoils having a pH greater than 4.0. Growth on the spoils was slow for the first 5 years, but total height exceeded that of Scotch pine (P. sylvestris), and red pine at 10 years.

    The bark of white pine is used as an astringent and an expectorant, and the wood has been used to produce white pine tar, which is used as an antiseptic, expectorant, and protective. White pine wood has medium strength, is easily worked, and stains and finishes well. It is used for furniture, patterns, matches, and many other items. White pine is also planted for Christmas trees. The foliage has a good color and responds well to shearing.

     

    Relationship with other species

    Non-human: Squirrels, chipmunks and mice feed on the seeds and soft needles. Inner bark is a preferred winter food of porcupine and deer browse the twigs. Rabbits may eat the bark of young trees. The seeds are eaten by red squirrels and such birds as crossbills and pine siskins. Pocket gophers graze the roots of seedlings and young trees. Snowshoe hares, white-tailed deer, and cottontails browse the foliage; the bark is eaten by various mammals. Young black bear cubs use large White Pine to climb to safety.

    Songbirds eat seeds. Bald eagles build nests in living White Pine, usually at a main branch located below the crown top. White Pine, especially those with broken tops, provide valuable habitat for cavity-nesting wildlife.

    Humans: Eastern white pine is an important timber tree for the production of softwood lumber. The wood is used for construction, cabinetry and furniture-making, handcrafts, and various other woodworking. Native American tribes used it extensively for various medicinal properties and it is an important food source for wildlife. The long history of cultivation has led to the development of numerous cultivars and forms. The species is affected by the exotic white pine blister rush Cronartium ribiola, an important pathogen of timber trees in the white pine group in temperate North America.

    Pests: There are a total of 277 insects and 110 disease organisms known to attack white pine. Only 16 insects and 7 diseases cause sufficient injury or mortality to be of concern. The three most important are white pine weevil (Pissodes strobi), white pine blister rust (Cronartium ribicola), and Armillaria mellea. The white pine weevil kills the terminal shoot, which may include the last 2 or 3 years of growth. The tree is seldom killed unless it is very small; lateral branches from the highest live whorl turn upward to produce new terminal shoots. Bole crook and loss of stem length result from this injury. There is evidence that white pine provenances differ in resistance to weevils but even the lowest levels of injury are unacceptable

    Some adelgids will appear as white cottony growths on the bark. All types produce honeydew which may support sooty mold. European pine shoot moth causes young shoots to fall over. Infested shoots may exude resin. The insects can be found in the shoots in spring. Pesticides are only effective when caterpillars are moving from overwintering sites to new shoots. This occurs when needle growth is about half developed.

    Bark beetles bore into trunks making small holes scattered up and down the trunk. The holes look like shot holes. Stressed trees are more susceptible to attack.

    Sawfly larvae are variously colored but generally feed in groups on the needles. Some sawfly larvae will flex or rear back in unison when disturbed. Sawflies can cause rapid defoliation of branches if left unchecked.

    Pine needle miner larvae feed inside needles causing them to turn yellow and dry up.

    Pine spittle bug lives and hides in a foamy mass.

    Zimmerman pine moth larvae bore into the trunk. The only outward symptoms may be death of parts of the tree or masses of hardened pitch on the branches.

    The larvae of pine weevils feed on the sapwood of the leaders. The leader is killed and the shoots replacing it are distorted. First symptoms are pearl white drops of resin on the leaders. The leaders die when the shoot is girdled as adults emerge in August. Prune out and burn infested terminals before July 15th.

    Diseases

    White pine blister rust attacks white Pine and uses the currant plant as an alternate host. European black currant, the favored alternate host, may be banned from certain areas. Other currants, particularly red currant should not be grown within 300 feet of Pines. Infected branches may be pruned off the pine.

    Canker diseases occasionally cause dieback of landscape pines. Keep trees healthy and prune out the infected branches.

    Needle cast is common on small trees and plantation or forest trees. Infected needles yellow and fall off.

     Other interesting facts

    • Cone production begins when 5-10 years old, but good seed production does not occur until trees are at least 20-30 years old. Good seed years every 3-5 years, with some seed produced in intervening years.
    • Seed dispersal primarily by wind. Seeds travel 200’ within a stand and more than 700’ in the open. Animals also disperse seeds. White-footed mice and red-backed voles bury caches containing seed beneath the litter but on top of the mineral soil. Caches that escape re-visitation and decimation produce seedlings.

    • Wood light, straight-grained and easily worked but not strong. Softwood with a soft to medium density. Color varies from creamy white to pale straw, with occasional contrasting orangish growth rings.
    • Moderately fire resistant; mature trees survive most surface fires due to thick bark, branch-free trunks, and a moderately deep rooting habit. Younger trees are not as fire resistant. Needles have relatively low resin content so are not highly flammable.

    • Distinguished by its commonly “windblown” or asymmetrical look; its large, long cones; and its five needles per cluster.

     

    Fun Facts:

    • White pine was a favorite tree of naturalist/author Henry David Thoreau.
    • Largest conifer of the eastern and upper Midwest forests, reaching 150 feet in height and up to 40 inches in diameter.
    • Pushed south and east during the last Ice Age by the southward expanding           White Spruce forest, which was to extend as far south as northern North Carolina and eastward out onto the Continental Shelf, White Pine was to weather the Ice Age at the extreme eastern edge of the Continental Shelf and perhaps in some as yet undiscovered pockets in the southern foothills of the Appalachians.
    • Native Americans were said to have used the inner bark as an emergency food source. The whitish resin which seeps out of the wounds of this tree was mixed with beeswax by the Iroquois and used to seal the seams of their canoes. 

     

    References

    http://dendro.cnre.vt.edu/dendrology/syllabus/factsheet.cfm?ID=111 

    http://www.rook.org/earl/bwca/nature/trees/pinusstrob.html 

    http://www.na.fs.fed.us/pubs/silvics_manual/Volume_1/pinus/strobus.htm

    http://www.discoverlife.org/mp/20o?search=Pinus+strobus&flags=col2:&res=640

    http://eol.org/pages/1061748/details

    http://hort.ufl.edu/database/documents/pdf/tree_fact_sheets/pinstrd.pdf

    Page drafted by Julia Giza