HE sojourner on our western plains where streams are few and sluggish, disappearing entirely in summer, soon learns to love the cottonwoods, for they will grow and cast their shade for men and cattle where no other tree could endure. The cottonwood may be unkempt and ragged, but it is a tree, and we are grateful to it for its ability to grow in unfavorable situations. In the Middle West it attains its perfection, although in New York we have some superb specimens—trees which are more than one hundred feet in height and with majestic trunks, perhaps five or six feet through. The deep-furrowed, pale gray bark makes a handsome covering. The trunk divides into great out-swinging, widely spaced branches, which bear a fine spray on their drooping ends. Sargent declares that at its best the cottonwood is one of the stateliest inhabitants of our eastern forests. The variety we plant in cities we call the Carolina poplar, but it is a cottonwood. It is a rapid grower, and therefore a great help to the "boom towns" of the West and to the boom suburbs in the East; although for a city tree its weak branches break too readily in wind storms in old age. However, it keeps its foliage clean, the varnished leaves shedding the dust and smoke; because of this latter quality it is of special use in towns that burn soft coal.
The cottonwood twigs which we gather for study in the spring are yellowish or reddish, those of last year's growth being smooth and round, while those showing previous growth are angular. The buds are red-brown and shining, and covered with resin which the bees like to collect for their glue. The leaf buds are slender and sharp-pointed; the flower buds are wider and plumper.
The two sexes of the flowers are borne on separate trees. The trees bearing pollen catkins are so completely covered with them that they take on a very furry, purplish appearance when in blossom. These catkins are from three to five inches long and half an inch thick, looking fat and pendulous; each fringed scale of the catkin has at its base a disc looking like a white bracket, from which hang the reddish purple anthers; these catkins fall after the pollen is shed and look like red caterpillars upon the ground.
The seed-bearing flowers are very different; they look like a string of little, greenish beads loosely strung. Each pistil is globular and set in a tiny cup, and it has three or four stigmas which are widened or lobed; as it matures, it becomes larger and darker green, and the string elongates to six or even ten inches. The little pointed pods open into two or more valves and set free the seeds, which are provided with a fluff of pappus to sail them off on the breeze; so many of the seeds develop that every object in the neighborhood is covered with their fuzz, and thus the tree has gained its name "cottonwood."
Staminate catkin of cottonwood.
Drawn by Anna Stryke.
The foliage of the cottonwood is like that of other poplars, trembling with the breeze. The heavy, sub-circular leaf is supported on the sidewise flattened petiole, so that the slightest breath of air sets it quaking; a gentle breeze sets the whole tree twinkling and gives the eye a fascinating impression as of leaves beckoning. The leaf is in itself pretty. It is from three to five inches long, broad, slightly angular at the base and has a long, tapering, pointed tip. The edge is saw-toothed, and also slightly ruffled except near the stem where it is smooth; it is thick and shining green above and paler beneath. The long, slender petiole is red or yellowish, and the leaves are placed alternate on the twigs.
In the autumn the leaves are brilliant yellow. The wood is soft, weak, fine-grained, whitish or yellowish, and has a satiny luster; it is not durable. It is used somewhat for building and for furniture, in some kinds of cooperage, and also for crates and woodenware; but its greatest use is for making the pulp for paper. Many newspapers and books are printed on cottonwood paper. It is common from the Middle States to the Rocky Mountains and from Manitoba to Texas.
Leading thought—The cottonwood is a poplar. It grows rapidly and flourishes on the dry western plains where other trees fail to gain a foothold. It grows well in the dusty city, its shining leaves shedding the smoke and dirt.
Method—Begin this study in spring before the cottonwoods bloom. Bring in twigs in February, give them water and warmth, and watch the development of the catkins. Afterwards watch the unfolding of the leaves and study the tree.
1. What is the color of the bark on the cottonwood? Is it ridged deeply? What is the color of the twigs? Are they round or angular, or both? Describe the winter buds and bud-scales. Can you tell which bud will produce leaves and which flowers?
2. Describe the catkin as it comes out. Has this catkin anthers and pollen, or will it produce seed? Do you think the seeds are produced on the same trees as the pollen?
3. Find a pollen-bearing catkin. Describe the stamens. Can you see anything but the anthers? On what are they set? What color are they? What color do they give to the tree when they are in blossom? What happens to the catkins after their pollen is shed?
4. Find a seed-bearing catkin. How long is it? Do you see why this tree is called the necklace poplar? Describe the pistils which make the beads on the necklace.
Seed-pod of poplar, shut and open.
5. When do the seeds ripen? If you have been near the tree, how do you know when they are ripe? How long is the catkin with the ripened seeds? How many balls on the necklace now? What is the color? How many seeds come out of each little pod? How are the seeds floated on the air? Why do we call this tree "cottonwood?"
6. How large is the largest cottonwood that you know? Sketch it to show the shape of the tree. Are the main branches large? Do they droop at the tips?
Courtesy of U. S. Forest Service.
7. How does the foliage of the cottonwood look? Does it twinkle with the wind? Examine the leaves upon a branch and see why they twinkle. Are the petioles round or flat? Are they flattened sidewise or up and down? Are they stiff or slender? Describe the leaves, giving their shape, veins, edges, color and texture above and below. Are the edges ruffled as well as toothed? Is the leaf heavy? If a breeze comes along how would it affect such a heavy, broad leaf on such a slender, thin petiole? Blow against the leaves and see how they move. Do you understand, now, why they twinkle? Can you see why the leaves shed smoke and dust, when used for shading city streets?
8. Why is the cottonwood used as a shade tree? Do you think it makes a beautiful shade tree? How long does it take it to grow? What kind of wood does it produce? For what is it used?
Supplementary reading—Trees in Prose and Poetry, pp. 139-149.
The growing fruit of the cottonwood.
Photo by Cyrus Crosby.