Black Locust

Robinia pseudoacacia

Origin


Black locust is native to the Appalachian Mountains from central Pennsylvania to northern Alabama and Georgia. It is also native to the Ozark Mountains of southern Missouri, north and west central Arkansas and eastern Oklahoma. It has been planted and naturalized as far north as Nova Scotia and in all the contiguous United States. It has become extensively naturalized in Europe as well as other areas where it has been introduced into cultivation. Even though black locust is native in the United States, it is not native to New England. It made its way to New England by being planted for utilitarian purposes, such as erosion control, and for its wood, which is considered to be one of the most durable in North America. The wood can be used for items such as fence posts and ladder rungs.

Identification/Habitat


Black locust is a fast-growing tree that can reach up to 100 feet in height. The roots have nitrogen-fixing nodules. The bark of the tree is gray to dark brown in color and is deeply furrowed. The white flowers with yellow centers are in dense racemes that can be 7-10 inches long.

The twigs of the tree have paired stipules that are modified into spines. The bluish-green leaves are alternate and odd-pinnately compound, with leaflets occurring in pairs except for the terminal leaflet. It is found in abandoned fields, edges, open disturbed areas, pastures, railroad right-of-ways, roadsides, utility right-of-ways, and vacant lots or yards. Since black locust does not tolerate low light situations, it is usually found in disturbed areas where it can get full sun. It prefers sandy, well-drained soils, and does not grow well in poorly-drained situations.

Dispersal

 
This tree mostly spreads by vegetative root suckers, though it can also spread via mechanical dispersal of its seeds.
Black Locust Large Tree View
Black Locust Leaves and Blooms

Problems

Due to the fact that black locust rapidly spreads via root suckers, it crowds out native vegetation. Damage to this plant only causes more root suckers and stump spouts to form. The seedlings also show this ability for rapid growth, however there is not a large amount of germination due to the inhibiting seed coat. It has been reported to grow up to 2 feet per year. Thus, it can form tall, dense, monotypic stands. It is also a great producer of nectar, which may allow it to compete with other species for pollinators.

Control


Hand pulling is acceptable for small saplings of this species, with mechanical removal and a "cut-and-dab" chemical treatment needed for larger trees. Simply mowing over saplings or cutting without follow up will likely be ineffective due to black locust's ability to spread by root suckers underground. Make sure to bag all foliage that may contain seeds to prevent the spread of the plant. Foliar spray is not recommended as it can be harmful to the surrounding floura and fauna. See the invasive removal page for how to carry out these methods. Any removal within 100 feet of wetland resource areas, including certified vernal pools, or within 200 feet of a perennial stream may require approval from the Concord Natural Resources Commission. Please contact the Division of Natural Resources before you begin.

Replacements


The following native plants can serve as a good replacement for black locust in a garden:
  • American linden (basswood) (Tilia americana)
  • Black gum (Nyssa sylvatica)
  • Black, red, scarlet, and white oaks (Quercus velutina, rubra, coccinea, and alba)
  • Eastern hop hornbeam (Ostrya virginiana)
  • Red and sugar maple (Acer rubrum and saccharum)
Black Locust View of Trunk