Species specifics: Black locust

Fast facts about black locust

Shrub-like, thorny tree that averages 70 feet tall.
Contains toxins that affect livestock including horses and cattle.
A notoriously difficult tree to control due to its ability to produce fast-growing saplings from cut or mowed stumps.

What to look for

Black locust (Robinia pseudoacacia) is a moderately sized shrub-like tree that averages 70 feet in height.

Black locust shares some similarities to honeylocust but has dark brown and deeply furrowed bark that branches in small limbs and compound leaves giving it a more shrub-like, brushier appearance than a honeylocust tree. Thorns on a black locust are small, paired and typically a half inch in length. Leaves are small, toothless, oval and appear in pairs down the leaf stalk (petiole).

The shrub produces drooping white to pink fragrant flowers in early summer that develop long, narrow seed pods that turn dark brown through the fall and winter. The tree can spread by both root suckers and seeds, creating dense thickets that will readily outcompete other favorable forages if left uncontrolled.

Most parts of the tree contain toxins that are toxic to most livestock including horses, cattle and small ruminants. Typically, animals avoid the trees, however, saplings and seeds can attract livestock even when other forages are readily available.

Where it is found

A native species to the Appalachian and Ozark regions, black locust has now become naturalized across all of the United States. It prefers moist or loamy soils but can also establish in clay and withstand periods of drought making disturbed or open pastures ideal for new populations to emerge.

How to treat it

Black locust readily resprouts after mechanical control including cutting, sending up shoots from buds located at the stump and throughout its root system. To prevent rapid regrowth, proper stump treatment is key.

For foliar applications, apply DuraCor® herbicide at 16 to 20 fluid ounces per acre with Remedy^® Ultra herbicide at 16 to 32 fluid ounces per acre, along with a non-ionic surfactant 0.25% volume/volume in late spring through summer when leaves have fully expanded.

For basal and cut-stump applications, use Remedy^® Ultra herbicide at 20 – 30% volume/volume in basal oil. Thoroughly spray the outer edge of the cut stump surface, including the bark down to the soil line, and treat any exposed roots to ensure maximum coverage.

This herbicide-plus-oil mixture may also be used for low-volume basal bark applications on black locust — as well as most other woody species — when treating stems less than 6 inches in diameter at the base.

Applications can be made year-round, provided snow cover or standing water does not interfere with coverage. Treatments made in late winter to early spring typically deliver the most consistent control.

Under normal field conditions DuraCor® is non-volatile. DuraCor has no grazing or haying restrictions for any class of livestock, including lactating dairy cows, horses (including lactating mares) and meat animals prior to slaughter. Label precautions apply to forage treated with DuraCor to manure and urine from animals that have consumed treated forage. DuraCor is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions. When using Remedy® Ultra, always read and follow label directions.