U.P. TREE IDENTIFICATION KEY
Quaking Aspen, Bigtooth Aspen, Cottonwood, and Balm-of-Gilead
Salicaceae, The Willow Family
The willow family has many tree and shrub species. World-wide there are about 335 species in two genera, Salix (willows) and Populus (aspens). The family is most abundant in temperate regions of the northern hemisphere with about 120 species in North America. Aspens are the most important part of the willow family, at least in the Lake States. Leaf stems, called petioles, are flattened (except in Balm-of-Gilead) which allow the leaves to flutter in even the slightest breeze. Male and female flowers occur on separate trees (so there are male and female trees). All members have male flowers arranged in catkins that bloom in the spring. Soon after, the female flowers ripen into tiny seeds that float through the are on milkweed-like fluffs. Cottonwood gets its name from these "cottony" seeds that are known for clogging up window screens. Although Populus is often a heavy seeder, regeneration is most commonly from root suckers. All family members have smooth, light-colored bark on trunks that are under a foot in diameter and on upper branches of large trees. Populus is short-lived, rapid-growing, and sun-loving. It commonly invades open ground but eventually gives way to tree species more tolerant of shade (a process called plant succession).
QUAKING ASPEN (Populus
Other Names: Popple, Poplar, Aspen, Trembling Aspen, Mountain Aspen
Key ID Features: Leaves, Bark, Buds
LEAVES are 2-4 inches long with small teeth along the margins. Leaf STEMS are flattest on quaking aspen, giving the tree the characteristic it is named after. BARK can be snow white, light gray, or a yellowish green. Black "beards" often form on the BARK below junctions with branches. BARK on large, old trees turns medium-gray and develops deep furrows. From a distance, quaking aspen is often mistaken for paper birch. TWIGS are light gray. The pointy BUDS are shiny brown and about a quarter-inch long and have several bud scales. Flower buds are much larger than the leaf buds. Aspen seldom grow as single individuals (although it looks like they do) but rather in clones from common root systems. Rapidly growing suckers from clearcut or storm-damaged stands are sometimes thought of as brush rather than young trees. Aspen commonly grows in stands with few other tree species. Trees can grow to HEIGHTS of 70-75 feet and 2 feet in DIAMETER, but not usually live much longer than 60-70 years. Quaking aspen is one of our most important trees for game species. Common pests: forest tent caterpillar, large aspen tortrix, leafminers, mourning cloak, tussock moths, aphids, Septoria canker, aspen shoot blight, Hypoxylon canker, Phellinus, beavers, leaf scorch.
BIGTOOTH ASPEN (Populus
Other Names: Popple, Poplar, Large-toothed Aspen
Key ID Features: Leaves, Bark, Buds
LEAVES from bigtooth aspen are similar to quaking aspen, except the margins have large teeth up to a quarter-inch long. In the spring, the LEAVES often have a woolly-like fuzz. BARK is usually more bronze-colored or olive-green, except on large trees. Terminal BUDS are larger than quaking aspen, but not so sharply pointed. Light gray twigs are a little stouter. Bigtooth aspen is a larger and longer-lived tree than quaking aspen. It usually occurs on better SOILS, such as silt loams. Bigtooth aspen is also a clonal species but also occurs with white pine, paper birch, and other upland hardwoods. Common pests: forest tent caterpillar, large aspen tortrix, leafminers, mourning cloak, tussock moths, aphids, Septoria canker, aspen shoot blight, Hypoxylon canker, Phellinus, beavers, leaf scorch.
Other Names: Balm, Bam, Balsam Poplar, Black Poplar, Tacamahac
Key ID Features: Leaves, Bark, Buds, Habitat
Balm is the WETLAND member of the aspen group. The LEAVES, however, are different. They have round leaf STEMS (petioles) and very finely-toothed leaf margins. Beginning fairly early in the season, the LEAVES usually develop a rusty or bronze cast, which can often be seen in the crown from a distance. The BARK is very similar to aspen. As the size increases, the BARK forms a plate-like texture that eventually grows into deep fissures. TWIGS are light gray, except the most recent twigs growth which may be more brownish. The pointy BUDS, especially the terminal BUD, are quite long and, when squashed, are very sticky with a distinct "balsamy" smell to them. Balm is clonal and often grows on the edge of wetlands and waterways but can invade open fields like quaking aspen. Usually growing in PURE STANDS, balm will also ASSOCIATE with ash, aspen, red maple, balsam fir, and white spruce. Common pests: large aspen tortrix, Septoria canker.
COTTONWOOD (Populus deltoides)
Other Names: Cottonwood, Eastern Poplar, Poplar, Southern Cottonwood
Key ID Features: Leaves, Bark, Buds, Size
Cottonwoods have distinctive triangular or "deltoid" LEAVES. The LEAF base is straight across or angled somewhat back toward the twig. Margins are toothed and the leaf is 3-5 inches long. TWIGS are yellowish-brown and have knobby leaf scars. BUDS are quite similar to balm-of-Gilead. BARK loses its smoothness earlier than the other Populus species. Older trees have gray-brown fissures that run deep into thick BARK. Cottonwoods can reach great DIAMETERS. It is not uncommon to find trees with trunks up to 5 or 6 feet across. HEIGHTS are commonly 70-90 feet. CROWNS are often large and spreading when open grown in old fields and around homesteads. Cottonwood can also be found along river courses.
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