Locust Trees are trees in the Robinia genus of the Robinieae tribe of the Robinioids clade of the Faboideae subfamily of the pea family. Other members of the Robinioids clade include Trefoils and Rattlebox. Other members of the Faboideae subfamily include pagoda trees, peas, milk vetch, lupines, camel thorn, scurfpeas, and clover.
Honey Locust Trees are in the Umtiza clade of the Caesalpinioideae subfamily of the pea family, so despite the similarity of their common names, they are not very closely related to the true locust trees described on this page.
Locust Street in north-central Woodland is likely named after locust trees. Its location between Walnut and Elm Streets suggests that it was more likely named after a type of tree than after locust insects.
Black Locust (Robinia pseudoacacia) is an invasive weed from the eastern United States. It is a fast-growing, short-lived, somewhat spiny, deciduous tree that usually grows 40 to 80 feet tall. In 20 years, it might grow to 40 feet tall. It visually resembles pagoda trees but differs in that it has spines and prickles, usually concentrated close to the ground and at the base of each compound leaf (not each individual leaflet). It prefers full sun. It requires good drainage and usually grows in dry areas. It reproduces asexually via root suckers, and the root system can be extremely hard to kill off after the tree has been cut down. It also reproduces by seeds. Black Locust has "perfect" flowers (containing both male and female parts).
U.C. Davis provides information on how to eradicate Black Locust.
The City of Woodland knowingly and intentionally plants Black Locust cultivars and hybrids all over town. The city favors the cultivar 'Purple Robe,' which tends to stay about half the size of the wild form, about 30 to 40 feet tall and 20 to 30 feet wide. The city has intentionally planted Robinia pseudoacacia 'Purple Robe' at Campbell Park, Charles Brooks Community Swim Center, Pioneer Park, and Woodland City Cemetery. This same cultivar is also planted by the city as a street tree on 1st Street, 2nd Street, 3rd Street, 4th Street, Court Street, Cross Street, Elm Street, Main Street, and Pendegast Street. In fact, the Urban Forest Resource Analysis published by the City of Woodland in 2018 indicated that the city was knowingly and intentionally maintaining 55 of these invasive weeds in Woodland.
Idaho Locust (Robinia × ambigua 'Idahoensis') is a hybrid of the invasive weed Black Locust (Robinia pseudoacacia) and the Clammy Locust (Robinia viscosa), which is a deciduous tree from the southeastern United States. It usually grows about 20 to 30 feet tall and equally wide. It prefers full sun or partial shade and requires good drainage. Idaho Locust has "perfect" flowers (containing both male and female parts). It is ranked 5 out of 10 on the Ogren Plant Allergy Scale, indicating that it has a mild to moderate tendency to cause hay fever. It is planted as a street tree on 1st Street, 2nd Street, 3rd Street, 4th Street, 5th Street, 6th Street, Beamer Street, Clover Street, County Road 102, Court Street, East Gibson Road, Elm Street, North Street, Palm Avenue, Pendegast Street, and Woodland Avenue. In fact, the Urban Forest Resource Analysis published by the City of Woodland in 2018 indicated that the city was knowingly and intentionally maintaining 91 of these invasive weed-descended hybrids in Woodland.
Links
California Invasive Plant Council: Robinia pseudoacacia
