Home › Volumes › Trees › How to Know the Trees

Key to Species — Part 15

A. Leaf stalks flattened.

B. Buds smooth, resinous.

C. Leaves triangular, coarsely serrate.

D. Blades of leaves 3 to 5 inches long.

(P. deltoidea) COTTONWOOD

DD. Blades of leaves 2 to 2 1/2 inches long.

E. Twigs slender, pubescent, yellow.

(P. Fremontii) COTTONWOOD

EE. Twigs stout, smooth, orange.

(P. Wislizeni) COTTONWOOD

CC. Leaves roundish, finely serrate.

(P. tremuloides) QUAKING ASP

BB. Buds downy; leaves ovate, coarsely toothed.

(P. grandidentata) GREAT-TOOTHED ASPEN

AA. Leaf stalks round; buds resinous.

B. Foliage green on both sides.

C. Shape of leaves lanceolate.

(P. angustifolia) NARROW-LEAVED COTTONWOOD

CC. Shape of leaves rhombic or deltoid, with long-pointed apex.

D. Margins finely serrate.

(P. acuminata) LANCE-LEAVED COTTONWOOD

DD. Margins coarsely and crenately toothed.

(P. Mexicana) MEXICAN COTTONWOOD

BB. Foliage pale, silvery or rusty below; margins finely serrate.

C. Buds thickly covered with yellow resin.

(P. balsamifera) BALM OF GILEAD

CC. Buds somewhat resinous.

D. Bark pale grey.

(P. trichocarpa) BLACK COTTONWOOD

DD. Bark reddish brown.

(P. heterophylla) SWAMP COTTONWOOD

Trees of the genus Populus form extensive forests in low, rich land and on high slopes of mountains. They attain large size, are quick of growth, and have exceeding tenacity of life, striking roots from twigs and sending up suckers from underground. Seeds are also a reliable means of reproduction, as they are produced in great numbers, and are widely scattered by the wind. The wood is one of the best materials for pulp making, and for a multitude of cheap wares for which a wood easy to work is demanded. The trees are largely planted for shade and ornament, for windbreaks, and to hold the banks of streams.

There are twenty-five species of Populus known, eleven of which are native to America. European species are often planted in this country, where they usually thrive as if at home. Some Russian varieties are successful on the Western prairies. China and Japan each have representative poplars here.

Cottonwood (Populus deltoidea, Marsh.)--Much-branched tree, 60 to 150 feet in height; diameter 5 to 7 1/2 feet. Bark deeply furrowed, grey-brown, becoming greenish; often ashen grey on old trees. Wood dark brown; sap wood white; weak, compact, light. Buds large, pointed, resinous. Leaves broadly ovate, taper pointed, 3 to 5 inches long, margin wavy and coarsely toothed, thick, shining, paler beneath, yellow in fall; petiole long, slender, flat, red or yellow. Flowers, March, in pendant catkins, 3 to 5 inches long, loosely flowered; staminate red, numerous; pistillate green, sparse on trees. Fruits, May, aments 6 to 12 inches long; capsules ovate, often curved, 2-velved; seeds in white, cottony mass. Preferred habitat, moist soil along streams. Distribution, Quebec to Northwest Territory; south to Florida; west to Colorado and New Mexico. Uses: Much planted for shade and windbreaks in the prairie states. Wood has recently come into use in making packing cases.

We all concede that the cottonwood has faults. The brittle wood cannot withstand the winds, the leaves drop untidily through the summer, the cast-off staminate catkins are a nuisance in spring, and the fluffy cottony seeds shed so deliberately in early summer by the fertile trees fill the air and the meshes of door and window screens to the exasperation of the whole neighbourhood.

But go out into one of the little breathing spaces called parks in a great city like New York in the early spring days when the children of the tenements and the stuffy flats are brought out for a first breath of the spring air. The old cottonwood has its buds all a-glisten with promise, and in a few days longer the dainty little leaves twinkle all over the treetop with the most cheerful green. In the late summer, in spite of its losses, the tree still carries a bright green crown of shade which turns yellow before it falls. With all its faults, it endures the heat of cities, and the dust and soot with commendable patience. In the protection of great buildings it does not suffer by winds as it does in exposed situations.

There are better, longer-lived trees for the open country, but in cities the cottonwood has a use and a message of cheer for rich and poor who look up and learn to know the tree. Unlike the variety next described, the cottonwood takes on dignity with added years.

The Carolina Poplar, considered a variety (Carolinensis) of the cottonwood above, is a strict pyramidal tree of vigorous and surprisingly rapid growth. In cities the varnish on the leaves evidently protects them from dust and smoke. Nurserymen have exploited this tree in America and Europe far beyond its merits, for though useful as a temporary tree, giving shade very soon, poplars should give way gradually to more permanent species planted with them. This poplar soon outgrows the beauty and luxuriance of its youth, and becomes broken and ugly. The immoderate planting of these trees gives a cheap character to many an otherwise handsome town or country place. New summer resorts and city "additions" show poplars in great numbers about their premises. The "poplar habit" is a very short-sighted one and expensive in the long run. J. Wilkinson Elliott, of Pittsburg, persuades his clients to plant Balm of Gilead, a much more satisfactory species.