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Broadleaved Trees of Yosemite National Park (1947) by C. Frank Brockman


BLACK LOCUST

Robinia pseudoacacia L. — Pea Family (Leguminosae)

Although native primarily to the Appalachian Mountain area, this tree has been widely planted throughout many parts of the United States. Yosemite Valley was no exception and those planted here during the early days are now good sized trees. They vary from six to fifteen inches in diameter and, in some cases, are from fifty to sixty feet high.

The black locust can be easily recognized by the alternate, odd-pinnately compound leaves, which are from eight to fourteen inches long, and which bear seven to nineteen sub-opposite rounded leaflets, each one and one-half to two inches long.

As this tree is a member of the Leguminosae or pea family its flowers and seed pods are characteristic of that group of plants. The handsome white clusters of pea-like flowers appear on the trees in June. Seeds, borne in elongated, dark brown, bean-like pods which are two to four inches long, are mature by late summer or early fall.

The trunk of this tree is short, dividing but a little way above the ground into a number of stout branches to form an open crown. The bark is dark reddish-brown in color and deeply fissured—the numerous ridges having a characteristic twisted or “ropey” appearance. The branches are characterized by the presence of numerous stout, short spines or prickles.

Foliage and flowers of black locust (Inch squares on background)
[click to enlarge]
Photo by Brockman

Foliage and flowers of black locust (Inch squares on background)


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