Black Locust

The black locust, also commonly called the false acacia, is a tree with incredibly invasive traits - so you might want to reconsider planting one. Arborists in our region advise against selecting black locusts due to the aggressive spread of their root suckers, which can crowd out other plants. Despite their fragrant white flowers for pollinators and soil erosion control, they often cause more harm than good in this area.

SCIENTIFIC NAME: Robinia pseudoacacia

HISTORY: Despite having such a negative image today, the black locust has been an historically important tree. It was once regarded as the toughest tree due to its resistance to rotting, and was used to build the poles of the first buildings in Jamestown, Virginia as well as the nails for American ships during the war of 1812 (aiding America to victory against the British, who used oak). Native Americans used black locusts to make bows and other tools.

LEAVES: The alternate, pinnately compound leaves can be up to a foot long, with 7-19 small ovoid or oval leaflets. They are bluish-green and barely change color in the fall.

FRUIT/CONE/NUT/SEED: The black locust produces flat brown legumes (or pods) that are typically about 4 inches long. However, the primary means of spread for black locusts is via root suckers.

FLOWERS: Black locusts produce fragrant white flower clusters in late May; they have five petals arranged in a pyramidal spike.

BARK: The bark is deeply ridged and furrowed, reddish-brown to black in color. It has an alternate branching pattern, creating a zigzag effect, with a pair of sharp thorns at each node.

HEIGHT: Black locusts can attain heights of 30-50 feet.

USES: This tree is useful for erosion control due to its ease of establishment, rapid early growth, and soil building. The wood has been used for fencing, mine timbers, and landscaping ties. While these trees are beneficial for insect pollinators, ingestion of any part of this tree is considered poisonous to both livestock and humans, and can be fatal.

SOURCES:

https://plants.usda.gov/DocumentLibrary/factsheet/pdf/fs_rops.pdf

https://www.fs.usda.gov/wildflowers/plant-of-the-week/Robinia-pseudoacacia.shtml

The Beardsley Avenue District Tree Tour is generously sponsored by Kallimani Tree Services.