balsam poplar

not listed

N5 - Secure

SNR - Unranked

not listed

FACW - Facultative wetland

FACW - Facultative wetland

FACW - Facultative wetland

Balsam poplar is a medium-sized to large, fast-growing, short-lived, deciduous tree with a single trunk. It is often the largest tree in a stand of trees. In areas with periodic flooding a new root system is produced after a flood. Roots develop at the newly-submerged base of the trunk in the recently deposited soil. The result is a multilayered root system. On wet sites not prone to flooding the roots are shallow and wide spreading and the trees are prone to windthrow. The tree also produces root suckers and is sometimes colonial, especially in dryer areas. In Minnesota mature trees are usually 40′ to 70′ tall and 4 ″ to 20″ in diameter at breast height, though large individuals can reach over 80′ in height and 24 ″ in diameter.

Young trees have a clearly defined bole, with the trunk is distinct to near the top of the crown. The crown on young trees is cone-shaped. On older trees the the trunk divides at the top into two or more equally dominant, ascending, major branches. Other branches are relatively short and ascending. The crown on older trees is rounded.

The bark on young trees is somewhat smooth, greenish-brown to greenish-gray, and sometimes tinged with red. It has numerous raised, diamond-shaped, lighter colored bumps (lenticels). The lenticels eventually become vertical cracks. As it ages the bark becomes thick and darker gray or grayish-brown. On the lower trunk the vertical cracks develop onto deep, narrow, V-shaped furrows between flat-topped ridges.

First-year twigs greenish and hairy. Second-year twigs are reddish-brown, shiny, and hairless or hairy, with bright orange lenticels. Third-year twigs are moderately stout, grayish-brown, and round in cross section. A cut twig shows a solid, star-shaped core of spongy cells (pith) and has a bitter aspirin taste.

The bud at the end of the twig (terminal bud) is reddish-brown, hairless, egg-shaped, round in cross section, and ⅝″ to ¾″ long. It is widest near the base and tapers to a sharp point at the tip. It is covered with 5 overlapping scales, is sealed with a red, sticky resin, and has a strong balsamic fragrance. Lateral buds are similar but narrower. They are appressed to the twig for most of their length but free at the tip. The first (lowest) scale is directly above the leaf scar. The leaf scars are nearly triangular and have 3 bundle scars. They are straight across at the top, not indented. There is no eyelash-like fringe of hairs where the bud meets the scar.

Two types of leaves are produced: early (preformed) leaves; and late (neoformed) leaves. Early leaves overwinter in the bud and are fully formed or almost fully formed before the buds burst in the spring. They are the first leaves to mature in the spring. Neoformed leaves are all of the subsequent leaves produced on long shoots. They are formed in the same season that they emerge.

All leaves are deciduous, alternate, and not lobed or divided (simple). They hang downward on yellowish, minutely hairy, flattened, ⅝″ to 2″ long leaf stalks (petioles). The petioles are round in cross section but may have a shallow channel on the dorsal (upper) surface. There are usually 0 or 2, rarely up to 5, warty glands at the point where the leaf blade attaches to the petiole. The leaf blades are egg-shaped to narrowly egg-shaped, 2″ to 3½″ long and 1¼″ to 2¼″ wide. They are 1.2 to 2.3 times as long as wide. They taper to a point at the tip with straight sides along the tip. Sometimes the tip is slightly extended with concave sides along the very tip. They are rounded or slightly heart-shaped at the base. The upper surface is dark green, shiny, and hairless. The lower surface is pale green, covered with a whitish, waxy coating, and hairless. There are usually some reddish-orange (copper-colored) resin stains on the lower surface. The margins of early leaves appear almost untoothed or are shallowly toothed with usually 20 to 35 teeth per side. The teeth are rounded, forward pointing, and distinctly curved. The margins of late leaves are similar but with deeper teeth and usually 30 to 45 teeth per side. The leaves turn yellow In autumn.

Male and female flowers are borne on separate trees. They appear before the leaves in early May to early June. Both male and female flowers are borne in crowded, pendulous, short-stalked or almost stalkless clusters (catkins) of usually 50 to 70 flowers. The catkins emerge from lateral buds on 2nd year twigs. Male catkins are 1½″ to 3½″ long, stout, and densely flowered. Each male flower has 20 to 30 stamens with anthers that are bright red before shedding pollen. Female catkins are 2⅜″ to 6¼″ long. The central axis (rachis) of the catkin is densely covered with short hairs. Female catkins elongate when fruiting, becoming 3½″ to 6¾″ long.

The fruit is an egg-shaped, ¼″ to ⅜″ long, 2-valved capsule. Each capsule contains 30 to 44 seeds. The seeds are released in late May to June. They have cottony hairs attached and are dispersed by wind.

40″ to 70″

The champion balsam poplar in Minnesota is on private property near Waskish, in Beltrami County. In 2019 it was measured at 87′ tall and 129″ in circumference (41″ in diameter), with a crown spread of 123′.

Yellowish-green

Plains cottonwood (Populus deltoides ssp. molinifera) petioles are conspicuously flattened. The leaves are broadly triangular in shape and proportionately wider. They are no more than one third as long as wide. The base of the leaf blade is squared off. The leaf underside is not stained with copper-colored blotches. The buds are not aromatic. The rachis of the catkin is hairless.

Quaking aspen (Populus tremuloides) leaves are proportionately wider. The petioles are conspicuously flattened. Male flowers have 40 to 80 stamens. Female catkins are no more than 2⅜″ long.

Moist. Boreal forests, aspen parklands, lakeshores, riverbanks, swamp margins, marsh edges. Full or partial sun. Very shade intolerant.

Early May to early June

Pemphigus populicaulis (no common name) is an aphid that causes a gall at the junction of leaf blade and petiole. The opening in the gall is a slit running parallel to the direction of the petiole.

The inner bark contains salacin, a precursor of aspirin.

Sources

2, 3, 4, 5, 7, 8, 28, 29, 30.

Native

Common in northern and central Minnesota, uncommon in the southeast, absent from the southwest.