The fragrant wax that saturates the winter buds and coats the young leaves in spring gives this tree its name. The bees find it as soon as the sap stirs and the wax softens. Quantities of it are collected and stored in hives "against a rainy day"; for this is what bees use to seal up weather cracks in their hives. It is known to bee keepers as "propolis." The service this wax renders the tree is to prevent the loss of water from the buds, and the absorption of more, after they are ready for winter. It is not "to keep the buds from freezing," as some people fondly imagine. The buds freeze solid, but it does them no harm. They are adjusted to it. In the far North the Indian uses the balsam of Balm of Gilead trees to seal up the seams of his birch-bark canoe, and of dishes and other utensils made of the same material.
The forests of Balm of Gilead stretch away over the lake margins and bottom lands of upper Canada, the largest and most prominent feature of vegetation in the vast regions that approach the Arctic circle, and extend down into the northern tier of states, from ocean to ocean.
The chief interest that centres about the tree is its good record when planted as a shade and ornamental tree, and in shelter belts. It is a hardy tree of excellent habit, compact and erect, but not too narrow for shade. It is easily propagated and transplanted, and grows rapidly. The tree is handsome, winter and summer. It has all the good points of the Carolina poplar, and lacks its fault of becoming so soon an unsightly cripple.
The Black Cottonwood (P. trichocarpa, Hook.) is the giant of the genus, reaching zoo feet in height and 7 to 8 feet in trunk diameter. It is tall and stately, with a broad, rounded crown supported upon heavy upright limbs. One of the beautiful sights of the Yosemite Park is the autumnal gold of black cotton wood groves whose abundant foliage embowers the stream borders at the altitude of about 4,000 to 5,000 feet. The tree's range covers the coast plain and western slopes of mountains from Alaska to southern California. The largest trees are on the
lowest levels. The dark rich green of the leaves gives this tree its name. They are ovoid, 3 to 4 inches long, with the finest of saw toothed margins. The wood has come into extensive use for the manufacture of various woodenwares and for staves of sugar barrels.
Swamp Cottonwood (Populus heterophylla, Linn.)—Round topped tree, 5o to go feet high. Bark red-brown, in narrow, loose plates; twigs red or grey, containing orange pith. Wood brown, light, compact. Buds resinous, ovate, with red scales. Leaves broadly ovate, 4 to 7 inches long, serrate, dark green with pale lining, when mature, covered with white tomentum as they unfold; petioles round, slender; yellow or brown in autumn. Flowers, March or April; staminate aments crowded, erect until blossoms open; anthers deep red; pistillate aments few-flowered, drooping. Fruit, May, aments 4 to 6 inches long; capsules few, 2 to 3-valved, I inch long, bell shaped. Preferred habitat, wet soil. Distribution, swamps from southern Connecticut to Georgia and Louisiana; north along Mississippi to Arkansas and Indiana.
The swamp cottonwood is variable in the base, apex and margin of its leaf. It may exhibit coarse or fine saw teeth, a blunt or sharp-pointed apex, a square or heart-shaped base. The conspicuous netted veins are always present, and the leaves are always large and broadly ovate, with slim, round petioles. The orange-coloured pith of the branchlets best distinguishes the tree from other poplars. The new shoots and the unfolding leaves are coated with white down. It often takes a whole summer to get rid of it.
The Acadians (probably) are responsible for the name langues de femmes, by which the tree is known in Louisiana. The mild calumny of Gerarde is thus perpetuated and extended to a species whose leaf stems are merely flexible, not flat at all! In the lumber trade the wood is known as "black poplar." It is dark brown in colour.