Читать книгу Studies of Trees - Jacob Joshua Levison - Страница 12

Distinguishing characters: The characteristic appearance of the full-grown tree is due to the drooping branchlets carried on main branches which bend upward (Fig. 7).

Leaf: The leaves are dark green in color and are arranged spirally, thus making the twigs coarser to the touch than the twigs of the hemlock or fir. In cross-section, the individual leaflet is quadrilateral, while that of the pine is triangular.

Form and size: A large tree with a straight, undivided trunk and a well-shaped, conical crown (Fig. 7).

Range: Northern Europe, Asia, northern North America.

Soil and location: Grows in cool, moist situations.

Enemies: The foliage of the spruce is sometimes affected by red spider, but is apt to be more seriously injured by drought, wind, and late frosts.

Value for planting: Commonly planted as an ornamental tree and for hedges. It does well for this purpose in a cool northern climate, but in the vicinity of New York City and further south it does not do as well, losing its lower branches at an early age, and becoming generally scraggly in appearance.

Fig. 8.—A Group of Hemlock.

Commercial value: The wood is light and soft and is used for construction timber, paper pulp, and fuel.

Other characters: The fruit is a large slender cone, four to seven inches long.

Comparisons: The white spruce (Picea canadensis) may be told from the Norway spruce by the whitish color on the under side of its leaves and the unpleasant, pungent odor emitted from the needles when bruised. The cones of the white spruce, about two inches long, are shorter than these of the Norway spruce, but are longer than those of the black spruce.

It is essentially a northern tree growing in all sorts of locations along the streams and on rocky mountain slopes as far north as the Arctic Sea and Alaska. It often appears as an ornamental tree as far south as New York and Pennsylvania.

The black spruce (Picea mariana) may be told from the other spruces by its small cone, which is usually only about one inch in length. In New England it seldom grows to as large a size as the other spruce trees.

It covers large areas in various parts of northern North America and grows to its largest size in Manitoba. The black spruce has little value as an ornamental tree.

The Colorado blue spruce (Picea parryana or Picea pungens) which is commonly used as an ornamental tree on lawns and in parks, can be told from the other spruces by its pale-blue or sage-green color and its sharp-pointed, coarse-feeling twigs. Its small size and sharp-pointed conical form are also characteristic.

It grows to a large size in Colorado and the Middle West. In the Eastern States and in northern Europe where it is planted as an ornamental tree, it is usually much smaller.

Fig. 9.—Twig of the Norway Spruce.