Black Locust Tree Information – The Down and Dirty

This post gives black locust tree information to include its ability to act as a fertilizer on other plants, how to propagate it, and the edible parts of this medicinal plant.

Black Locust Tree Information - Black Locust Flower

Black Locust Tree Information – Black Locust Flower

Black Locust (Robinia pseudoacacia) is a deciduous tree in the pea family that can be used as a fertilizer with its nitrogen fixing capabilities.  It is native to the southeastern United States but can now be found throughout most of North America as it is USDA hardiness rated from zones 4 to 8.  It can grow up to 80 feet tall, but it usually stays between 30 and 50 feet in height. Black Locusts prefer sandy or rocky soil, and are most often found in old fields, open areas, woods, and along stream sides.

Black Locust Tree Information

The leaves are pinnate with 9–19 oval leaflets.  Leaflets are always paired, except for the one on the end of the leaf. Each leaf usually has a pair of short spines at the base.  The leaflets fold together in wet weather and at night. Leaf color is bluish-green on top, and pale underneath. The entire leaf is 6 to 12 inches long. Leaflets are oval-shaped and less than 2 inches long with no teeth and a bristle tip.

The very fragrant (smell similar to orange blossoms) flowers are white to lavender or purple and are about ¾ inches long and pear-shaped.  They each have five white petals, and many flowers grow together in a droopy cluster, 4 to 8 inches long. The flowers appear in May or June after the leaves break bud. The flowers give way to a snap pea looking fruit.  The fruit is a legume containing 4 to 10 seeds.

Black Locust Tree Information

It has thick, deeply furrowed blackish bark. The wood is Pale yellowish brown; heavy, hard, strong, close-grained and very durable in contact with the ground.  Because the wood is extremely hard, resistant to rot, and durable it is often used for fence posts.  Fresh cut wood has somewhat of an offensive odor, but that disappears with time.  It is one of the heaviest and hardest woods in North America.  For firewood it burns slowly, hot, and with little smoke.

It can act as erosion control.  Black locust ordinarily produces a shallow and wide-spreading root system that is excellent for soil binding but is also capable of producing deep roots. It acts as a nitrogen fixer for the soil allowing this tree to act as a fertilizer.


Black Locust Tree Information - Black Locust

Black Locust Tree Information – Black Locust

Although it is a good seed producer, it primarily spreads by underground shoots. If planting by seed, you must scarify the seeds prior to planting.  Black locust is easily propagated from softwood, hardwood, and root cuttings.


Although the bark and leaves are toxic, various reports suggest that the seeds and flowers are edible.  The flowers are eaten in France and Japan.  I have found several sources saying that the seeds are edible but the pods are poisonous.


“Febrifuge. The flowers are antispasmodic, aromatic, diuretic, emollient and laxative. They are cooked and eaten for the treatment of eye ailments. The flower is said to contain the antitumor compound benzoaldehyde. The inner bark and the root bark are emetic, purgative and tonic. The root bark has been chewed to induce vomiting, or held in the mouth to allay toothache, though it is rarely if ever prescribed as a therapeutic agent in Britain. The fruit is narcotic. This probably refers to the seedpod. The leaves are cholagogue and emetic. The leaf juice inhibits viruses.” *



*These statements have not been evaluated by the Food and Drug Administration.  This product is not intended to diagnose, treat, cure or prevent any disease.

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