Robinia pseudoacacia, or Black Locust, are trees in the pea family, Fabaceae. It is native to the southeastern United States, but has been widely planted and naturalized elsewhere in temperate North America and does best on rich moist limestone soils. In the Bluegrass Region, many farmers call the Black Locust "trash trees" because they spring up voluntarily in fields, fencerows and lawns, but for smell, you can beat the blossoms of the Locust tree.
With a trunk up to 2 1/2 feet in diameter, the Black Locust has thick, deeply furrowed blackish bark. This tree can grow to an average of 30-50 feet tall, with some instances of 80 foot tall specimens. The leaves are 8 to 10 inches long and each leaf usually has a pair of short thorns at the base. The intensely fragrant flowers are white and are considered edible. The fruit is a legume 4-5 inches long, containing 4-10 seeds.
Black Locust is a major honey plant in eastern USA. The flowering stage starts in spring, but the blooming period is short (about 10 days) and it does not consistently produce a honey crop year after year. Weather conditions can have quite an effect on the amount of nectar collected as well.
The hard wood of the Black Locust is resistant to rot and long lasting, making it an excellent wood for fence posts and small watercraft. It is highly valued as firewood for wood-burning stoves because it burns slowly, with little visible flame or smoke, and has higher heat content than any other species in the Bluegrass Region. It is also planted for firewood because it grows rapidly, is highly resilient in a variety of soils, and it grows back even faster from its stump after harvest by using the existing root system. Black Locust is important because it is a nitrogen-fixing species - a nitrogen-fixing tree and shrub species is of great importance in managed forestry.
Black Locust reproduces through its distinctive hanging pods, which are easily carried long distances by the wind. However, every part of the tree, especially the bark, is considered TOXIC with the exception of the flowers. Since the Bluegrass is the Horse Capital of the world, it is important to keep horses away from Black Locust trees. Horses that graze on young Locust sprouts or Black Locust leaves may show signs of anorexia, depression, diarrhea, colic, weakness, and cardiac arrhythmia. Symptoms usually occur about 1 hour following consumption, and immediate veterinary attention is required.