Studies of Trees Part 6

AMERICAN ELM (_Ulmus americana_)

Distinguishing characters: The tree can be told at a glance by its general branching habit. The limbs arch out into a wide-spreading *fan or vase-like crown* which loses itself in numerous fine drooping branchlets. See Fig. 37.

[Ill.u.s.tration: FIG. 37.--American Elm.]

Leaf: The leaves are simple, alternate, and from 2 to 5 inches long.

[Ill.u.s.tration: FIG. 38.--English Elm in Winter.]

Form and size: It is a tall tree with a trunk that divides a short distance above ground. Its general contour, together with the numerous branches that interlace its ma.s.sive crown, give the elm an interesting and stately appearance which is unequaled by any other tree.

[Ill.u.s.tration: FIG. 39.--Lombardy Poplar.]

Range: Eastern North America.

Soil and location: The elm prefers a deep, rich and moist soil, but will adapt itself even to the poor soil of the city street.

Enemies: _The leopard moth_, a wood-boring insect, and the _elm leaf beetle_, a leaf-eating insect, are the two most important enemies of the tree. Their ravages are very extensive.

Value for planting: The tree has a character of its own which cannot be duplicated for avenue or lawn planting.

Commercial value: The wood is strong and tough and therefore has a special value for cooperage, agricultural implements, carriages, and shipbuilding.

Other characters: The _buds_ are small, brown, and smooth, while those of the European elms are covered with down. The _small side twigs_ come out at almost right angles to the larger terminal twigs, which is not the case in other species of elm.

[Ill.u.s.tration: FIG. 40.--Leaf of Carolina Poplar.]

Other common names: _White elm_.

Comparisons: The _English elm_ (_Ulmus campestris_) is also a tall, dignified tree commonly seen under cultivation in America, but may be told from the American species by the difference in their general contour. The branches of the English species spread out but do not arch like those of the American elm, and the bark of the English elm is darker and coa.r.s.er, Fig. 38. Little tufts of dead twigs along the main branches and trunk of the tree are characteristic of the English elm and will frequently help to distinguish it from the American elm.

The _Camperdown elm_ may be recognized readily by its dwarf size and its low drooping umbrella-shaped crown.

LOMBARDY OR ITALIAN POPLAR (_Populus nigra, var. italica_)

Distinguishing characters: Its *tall, slender, spire-like form* and rigidly *erect branches*, which commence low on the trunk, make this tree very distinct at all seasons of the year. See Fig. 39.

Leaf: Triangular in shape, similar to that of the Carolina poplar but smaller, see Fig. 40.

Range: Asia, Europe, and North America.

Soil and location: The poplar is easily grown in poor soil, in any location, and is very hardy.

Value for planting: The tree has a distinctive form which makes it valuable for special landscape effects. It is also used for shelter belts and screening. Like all poplars it is short lived and will stand pruning well.

Commercial value: None.

[Ill.u.s.tration: FIG. 41.--Carolina Poplar.]

Comparisons: The _Carolina poplar_, or Cottonwood (_Populus deltoides_) can be told from the Lombardy poplar by its wider crown and its more open branching, Fig. 41. It may be recognized by its big terminal twigs, which are light yellow in color and coa.r.s.er than those of the Lombardy poplar, Fig. 42. Its bark is smooth, light and yellowish-green in young trees, and dark gray and fissured in older specimens. Its large, conical, glossy, chestnut-brown bud is also characteristic, Fig. 42. Its flowers, in the form of large catkins, a peculiarity of all poplars, appear in the early spring. The Carolina poplar is commonly planted in cities because it grows rapidly and is able to withstand the smoke and drouth conditions of the city. Where other trees, however, can be subst.i.tuted with success, the poplar should be avoided. Its very fast growth is really a point against the tree, because it grows so fast that it becomes too tall for surrounding property, and its wood being extremely soft and brittle, the tree frequently breaks in windstorms. In many cases it is entirely uprooted, because it is not a deep-rooted tree. Its larger roots, which spread near the surface, upset the sidewalk or prevent the growth of other vegetation on the lawn, while its finer rootlets, in their eager search for moisture, penetrate and clog the joints of neighboring water and sewer pipes. The tree is commonly attacked by the _oyster-sh.e.l.l scale_, an insect which sucks the sap from its bark and which readily spreads to other more valuable trees like the elm.

The female form of this tree is even more objectionable than the male, because in the early spring the former produces an abundance of cotton from its seeds which litters the ground and often makes walking dangerous. The only justification for planting the Carolina poplar is in places where the conditions for tree growth are so poor that nothing else will grow, and in those cases the tree should be cut back periodically in order to keep it from becoming too tall and scraggly. It is also desirable for screening in factory districts and similar situations.

[Ill.u.s.tration: FIG. 42.--Bud of the Carolina Poplar.]

The _silver_ or _white poplar_ (_Populus alba_) may be told from the other poplars by its characteristic smooth, _whitish-green bark_, often spotted with dark blotches, Fig. 43. The _leaves are silvery-white_ and downy on the under side. The twigs are dark green in color and densely covered with a white down. It grows to very large size and forms an irregular, wide-spreading, broad head, which is characteristically different from that of any of the other poplars.

[Ill.u.s.tration: FIG. 43.--Bark of the Silver Poplar.]

The _quaking aspen_ (_Populus tremuloides_), the _large-toothed aspen_ (_Populus grandidentata_) and the _balsam poplar_ or _balm of Gilead_ (_Populus balsamifera_) are other common members of the poplar group. The quaking aspen may be told by its reddish-brown twigs, narrow sharp-pointed buds, and by its small finely toothed leaves. The large-toothed aspen has thicker and rather downy buds and broader and more widely toothed leaves. The balsam poplar has a large bud thickly covered with a sticky, pungent, gelatinous substance.

GINGKO OR MAIDENHAIR TREE (_Gingko biloba_)

[Ill.u.s.tration: FIG. 44.--Gingko Trees.]

Distinguishing characters: The *peculiar branches* of this tree *emerge upward* from a straight tapering trunk *at an angle of about 45*

and give to the whole tree a striking, Oriental appearance, which is quite different from that of any other tree, Fig. 44.

Leaf: Like that of a leaflet of maidenhair fern, Fig. 45.

Range: A native of northern China and introduced into eastern North America.

Soil and location: The gingko will grow in poor soils.

Enemies: Practically free from insects and disease.

[Ill.u.s.tration: FIG. 45.--Leaves of the Gingko Tree.]

Value for planting: It makes a valuable tree for the street where heavy shade is not the object and forms an excellent wide-spreading specimen tree on the lawn.

Other characters: The _fruit_ consists of a stone covered by sweet, ill-smelling flesh. The tree is dioecious, there being separate male and female trees. The male tree is preferable for planting in order to avoid the disagreeable odor of the fruit which appears on the female trees when about thirty years old. The male tree has a narrower crown than the female tree. The buds (Fig. 46) are very odd and are conspicuous on the tree throughout the winter. The leaves of the gingko shed in the winter. In this respect the tree is like the larch and the bald cypress.

[Ill.u.s.tration: FIG. 46.--Bud of the Gingko Tree.]

The gingko belongs to the yew family, which is akin to the pine family. It is therefore a very old tree, the remains of the forests of the ancient world. The gingko in its early life is tall and slender with its few branches close to the stem. But after a time the branches loosen up and form a wide-spreading crown. In the Orient it attains enormous proportions and in this country it also grows to a fairly large size when planted on the open lawn or in groups far apart from other trees so that it can have plenty of room to spread. It then produces a picturesque effect of unusual interest.

WEEPING WILLOW (_Salix babylonica_)

Distinguishing characters: All the willows have a single cap-like scale to the bud, and this species has an unusually *drooping ma.s.s of slender branchlets* which characterizes the tree from all others, Fig. 47.

[Ill.u.s.tration: FIG. 47.--Weeping Willow.]

Form and size: It grows to large size.

Range: Asia and Europe and naturalized in eastern United States.

Soil and location: Prefers moist places near streams and ponds.