Robinia pseudoacacia. BLACK LOCUST. Appalachians, Ozarks
Robinia x ambigua
LEGUMINOSAE (Pea family)

A largish tree of very pleasant appearance in April when it is clothed in new light green leaves and strings of faintly fragrant pea flowers. The compound leaves have about 13 thin oval leaflets, each 1 to 2 inches long, and at the base of the leaf stalk wicked spines about 1/2 inch long are found on older trees. More recently the spineless variety 'Inermis' has been favored. Last season's thin brown pods, which are about 3 inches long, contain a few flat brown seeds. The wood was used in the United States where hardness and durability were wanted, for example it was used by the Native Americans for bows. Introduced into France in 1601 by botanist Jean Robin, the tree became well known in Europe. In France it is used as an ornamental, has been extensively planted for firewood, and the flower clusters are dipped in batter and deep fried. It is naturalized over much of Italy under the name Acacia (pronounced a-HAH-shah in Tuscany) and the flowers are eaten by children for the nectar. Native Americans ate the flowers and cooked the pods and seeds.

Look for one on Memorial Way near the honey locust and carob trees. A variety with pale pink flowers grows inside Frost Amphitheater on the slope west of the stage. A dozen of variety ‘Frisia’ have been planted as the forest in the lawn of the inside courtyard at Clark Center, and 11 more are outside. New growth is nearly orange, mature leaves yellow.

Older plantings at the northwest end of Mayfield Avenue have been supplemented by colorful varieties at both ends of the stretch between Santa Ynez Street and Santa Fe Avenue. These new additions are R. × ambigua, a cross between R. pseudoacacia and R. viscosa; the name of this Mayfield Avenue cultivar is ‘Decaisneana’. Another showy cultivar of R. × ambigua known as ‘Idahoensis’, with bright-colored flowers, can be seen in the area around Mirada Avenue and Frenchman’s Road, and there is an extensive formal planting of 60 trees (1999) surrounding the Stone Pine Plaza (Science and Engineering Quad). Many more young locusts are on the North-South Mall, from Gilbert Biosciences to Keck Science Building. The plants close to Keck are R. × ambigua ‘Purple Robe’.

Illus.: McMinn, Howard E. and Evelyn Maino. 1951. An illustrated manual of Pacific coast trees; with lists of trees recommended for various uses on the Pacific coast by H. W. Shepherd. 2d ed. Berkeley, Calif.: University of California Press.

Illustrations (links open new windows): Silhouettes from Trees of Stanford & its Environs

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Related material: Canopy Trees for Palo Alto Tree Library

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