(balsam poplar)Select an option below for more information on this species
Balsam poplar is a deciduous tree in the willow family (Salicaceae) that has the widest geographic distribution of any tree in Alaska (even growing in isolated floodplain sites on the Arctic slope). It is a ruderal species, quickly becoming established following disturbance in gravel bars, fire-disturbed sites and open soil of steep slopes. The straight trunk grows 15-20 m tall, with diameters reaching >30 cm. Its bark is gray, smooth when young, with dark scars, becoming deeply furrowed at the base in maturity.
The leaves are ovate, 6-11 cm long by 4-7.5 cm wide, with a finely crenate margin, and pointed tip. Leaves are shiny dark green above and pale green with rusty brown veins beneath. Twigs are reddish when young, becoming gray-brown and knobby with circles of leaf scars. The lightweight, soft wood is white with brown heartwood.
Balsam poplar trees have a conical, open crown, maturing into a rounded shape, usually with branches beginning halfway or higher up the trunk. Long branches account for the height and width for the crown, and the leaves are produced on smaller shoots from the main branches. Buds of leaves and flowers are covered in a sticky, aromatic resin, the source of the name 'balsam'. Winter buds are 1-3 cm long, long-pointed, shiny red-brown and also covered in resin.
The trees are dioecieous, with wind-pollinated male and female flowers borne on separate individuals. Male and female inflorescences are highly reduced. Male plants have catkins with many staminate flowers, 20-30 red-purple stamens per flower. Female catkins are 5-9 cm long, with many small flowers, each having round discs beneath two fused carpels and broad stigmas. The capsules are round and green, maturing to brown and opening along two seams (as opposed to black cottonwood's three). Each seed is attached to many long white hairs, which catch the wind and disperse the seeds, or float and carry seeds downriver. The other common name, cottonwood, refers to the mass of white, fluffy hairs attached to the seeds.
Balsam poplar can be distinguished from quaking aspen (Populus tremuloides) by the much larger, lanceolate and glossy leaves, petioles that are round in cross-section, furrowed bark in older trees and difference in habitat. Alaskan birch (Betula neoalaskana) can at first glance look similar, but the bark of balsam poplar is never papery, and the leaves are not serrated.
Trees are sometimes used as lumber or firewood. The resin was widely used by Alaska Natives as a balm. Cottonwood growth buds are collected in spring and used to make a tincture for an all-purpose healing salve, used on skin, various types of injuries and irritation, toothaches, sore throats, and congestion (Garibaldi 199). The cambium of young easily peeled trees have also been used as a laxative.
Balsam poplar is native to boreal North America where its range spans from Alaska across Canada to Labrador and Newfoundland, the northeastern United States and across the upper Midwest, reaching its southern limit in Colorado, Illinois and West Virginia. Balsam poplar is the most widely distributed tree species in Alaska, having the farthest north localities of any tree, reaching the north side of the Brooks Range. The range of balsam poplar in Alaska spans from the eastern border west through the Noatak River valley, all but the northwestern edge of the Seward Peninsula, down through interior to Kodiak Island, and west to Chignik on the Alaska Peninsula. Hybrids with P. trichocarpa occur where their ranges overlap along the southern coast and transitional areas. In Denali, balsam poplar is widespread, found near all the major rivers in the Park, as well as steep slopes into the alpine.
Details are shown in the Plots & Charts found at right, depicting recent Denali data.
Balsam poplar is most abundant at 300-500 m in Denali National Park. Its elevational tolerance ranges from the lowest elevations in the park to 1356 m. This species is more common on southern aspects, where it has a wider tolerance of both elevation and incline, and reaches a higher level of cover. Balsam poplar is most commonly found either on sites with no incline, or on steep to extremely steep slopes (>28 degrees), where white spruce in particular cannot compete.
Details are shown in the Plots & Charts found at right. For more on how to interpret these figures, visit Understanding Data Presented.