Forest Trees of Illinois Part 9

[Ill.u.s.tration: HONEY LOCUST

Twig, three-quarters natural size. Leaf, one-quarter natural size.]

The _leaf_ is pinnate, or feather-like with 18 to 28 leaflets; or it is twice-pinnate, consisting of 4 to 7 pairs of pinnae or secondary leaflets, each 6 to 8 inches long and somewhat resembling the leaf of the black locust.

The _flowers_ which appear when the leaves are nearly full-grown are inconspicuous, greenish-yellow and rich in honey. The petals vary from 3 to 5, the stamens are 3 to 10 and the ovary is wooly and one-celled.

The _fruit_ is a pod, 10 to 18 inches long, often twisted, 1 to 1-1/2 inches wide, flat, dark brown or black when ripe and containing yellow sweetish pulp and seeds. The seeds are very hard and each is separated from the others by the pulp. The pods are eaten by many animals, and as the seeds are hard to digest, many are thus widely scattered from the parent tree.

The _wood_ is coa.r.s.e-grained, hard, strong and moderately durable in contact with the ground. It is used for fence posts and crossties. It should not be confused with the very durable wood of the black locust.

The water locust, _Gleditsia aquatica_ Marsh., is found in river bottoms in southern Illinois, becoming a medium sized tree. It may be known by its short pods, 1 to 2 inches long, with only 2 or 3 seeds.

+REDBUD+ _Cercis canadensis_ L.

THE redbud is a small tree occurring under taller trees or on the borders of fields or hillsides and in valleys throughout the State. It ordinarily attains a height of 25 to 50 feet and a diameter of 6 to 12 inches. Its stout branches usually form a wide flat head.

[Ill.u.s.tration: REDBUD

Leaf, one-fourth natural size. Twig, and flowers, two-thirds natural size.]

The _bark_ is bright red-brown, the long narrow plates separating into thin scales.

The _leaves_ are alternate, heart-shaped, entire 3 to 5 inches long and wide, glossy green turning in autumn to a bright clear yellow.

The conspicuous bright purplish-red, pea-shaped _flowers_ are in cl.u.s.ters along the twigs and small branches and appear before or with the leaves in early spring.

The _fruit_ is an oblong, flattened, many seeded pod, 2 to 4 inches long, reddish during the summer, and often hanging on the tree most of the winter.

The _wood_ is heavy, hard, not strong, rich, dark brown in color, and of little commercial importance. The redbud is cultivated as an ornamental tree and for that purpose might be planted more generally in this State.

The Kentucky coffee-tree, _Gymnocladus dioicus_ K. Koch, though not anywhere a common tree, is found on rich bottom lands throughout the State. The much-divided leaves are 2 to 3 feet long. The pods are 5 to 8 inches long and 1 to 2 inches wide and contain hard seeds 3/4 inch long. It has few qualities to recommend it for ornamental planting.

+BLACK LOCUST+ _Robinia pseudoacacia_ L.

THE black locust is a native to the Appalachian Mountains but has been introduced into Illinois, and now occurs throughout the entire State growing on all soils and under all conditions of moisture except in swamps. It is found generally in thickets on clay banks and waste places or along fence rows.

[Ill.u.s.tration: BLACK LOCUST

Leaf, one-third natural size. Twig and flower, two-thirds natural size.]

The twigs and branchlets are armed with straight or slightly curved sharp, strong spines, sometimes as much as 1 inch in length which remain attached to the outer bark for many years. The _bark_ is dark brown and divides into strips as the tree grows older.

The _leaves_ are pinnate, or featherlike, from 6 to 10 inches in length, consisting of from 7 to 19 oblong thin leaflets.

The _flowers_ are fragrant, white or cream-colored, and appear in early spring in graceful pendent racemes. The _fruit_ is a pod from 3 to 5 inches long containing 4 to 8 small hard seeds which ripen late in the fall. The pod splits open during the winter, discharging the seeds. Some seeds usually remain attached to each half of the pod; the pod thus acts as a wing upon which the seeds are borne to considerable distances before the strong spring winds.

The _wood_ is yellow in color, coa.r.s.e-grained, very heavy, very hard, strong, and very durable in contact with the soil. It is used extensively for fence posts, poles, tree nails, insulator pins and occasionally for lumber and fuel.

The tree is very rapid in growth in youth but short-lived. It spreads by underground shoots and is useful for holding and reclaiming badly gullied lands. The usefulness of the black locust is, however, very greatly limited by the fact that it is subject to great damage from an insect known as the locust borer.

+TREE OF HEAVEN+ _Ailanthus altissima_ Swingle

THIS tree is a native of China but planted in Illinois because of its tropical foliage. It has escaped and become naturalized. It is a handsome, rapid-growing, short-lived tree, attaining a height of 40 to 60 feet, and a trunk diameter of 2 to 3 feet. Its crown is spreading, rather loose and open. The twigs are smooth and thick with a large reddish-brown pith. The _winter buds_ are small, globular and hairy, placed just above the large leaf-scars.

[Ill.u.s.tration: TREE OF HEAVEN

Twig, one-half natural size. Leaf and fruit, one-fourth natural size.]

The _leaves_ are alternate, pinnately compound and one to three feet long. The leaflets number from 11 to 41, are smooth, dark green above, paler beneath, turning a clear yellow in autumn.

The _flowers_ appear soon after the leaves are full grown, on different trees, borne in large upright panicles. They are small yellow-green in color with 5 petals and 10 stamens. The staminate flowers have a disagreeable odor.

The _fruit_, ripening in October but remaining on the tree during the winter, is a one-seeded samara, spirally twisted, borne in crowded cl.u.s.ters.

The tree of heaven is useful for landscape planting, succeeding in all kinds of soils and all kinds of growing conditions. It makes a rapid showing and is practically free from all diseases and insect injury.

+SMOOTH SUMAC+ _Rhus glabra_ L.

THE smooth sumac is usually a tall shrub but occasionally it develops as a tree 20 to 25 feet tall with a trunk diameter of 6 to 10 inches. A few large spreading branches form a broad, flat, open head. The twigs are smooth and glabrous and have a thick, light brown pith with small round winter buds.

[Ill.u.s.tration: SMOOTH SUMAC

Twig, one-half natural size. Leaf and fruit, one-fourth natural size.]

The compound _leaves_ are 6 to 18 inches long, composed of 9 to 27 leaflets with sharply notched margins. They are dark green above, whitish beneath, changing to red, purple and yellow early in the autumn.

The _flowers_ are small and green, produced in dense terminal panicles.

The _fruit_ is a small globose berry, covered with crimson hairs and has a pleasant acid taste. The conspicuous deep red panicles of fruit remain unchanged on the tree during the winter.

The _wood_ is light and of a golden yellow color. Either as a tree, or as a shrub, the smooth sumac is excellent for ornamental planting, being particularly desirable on terraces or hillsides, where ma.s.s effects are desired. It transplants very readily and spreads freely.

The staghorn sumac, _Rhus typhina_ L., is a slightly taller tree, as it reaches a height of 20 to 35 feet, and a stem diameter of 8 to 12 inches. The twigs and leaves are similar to those of the smooth sumac but are conspicuously hairy. Its occurrence is limited to the northern part of the State.

The s.h.i.+ning sumac, _Rhus copallina_ L., usually occurs in shrub form but it occasionally reaches a height of 20 feet with a stem diameter of 6 inches. The leaves are smooth above but somewhat hairy beneath with a winged rachis and about 9 to 21 leaflets that are slightly toothed. Late in the summer its foliage turns a brilliant red. The fruit cl.u.s.ters are much smaller than the preceding species. It is found throughout the State.

+SUGAR MAPLE+ _Acer saccharum_ Marsh.

THE sugar maple is an important member of the climax forests which stretch from Maine to Minnesota and southward to Texas and Florida. It is an a.s.sociate of the hemlocks and the birches in the North, with the beeches and chestnuts through the middle states, with the oaks in the West and with the tulip and the magnolias in the South. In Illinois it is a common and favorite tree throughout the State. In the open it grows fairly rapidly and has a very symmetrical, dense crown, affording heavy shade. It is, therefore, quite extensively planted as a shade tree. The _bark_ on young trees is light gray and brown and rather smooth, but as the tree grows older, it breaks up into long, irregular plates or scales, which vary from light gray to almost black. The twigs are smooth and reddish-brown, and the _winter buds_ are smooth and sharp-pointed.

The tree attains a height of more than 100 feet and a diameter of 3 feet or more. The sap yields maple sugar and maple syrup.

[Ill.u.s.tration: SUGAR MAPLE

Leaf, one-third natural size.