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, coarse-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.
[Illustration: TREE OF HEAVEN