Black locust tree thorns are poisonous and sharp, growing up to 2 inches in length. They may cause severe stomach pain or death when ingested by people, livestock or other animals such as deer, or house pets. Thorns also pose a poking or scratching hazard; though being scratched by a thorn isn't poisonous, it can hurt. Thorns on branches low enough may poke an individual or child in the eye.
An individual can also injure his foot by stepping on a black locust tree thorn while wearing thin shoes, as the thorn can easily pass through such material. Thorns may pop or tear inflatable and plastic equipment, such as pools, plastic water slides and bounce houses, even if the inflatable item has a rubber lining. A black locust tree may attract crows. Many consider crows a nuisance, since they often eat vegetable gardens when available.
Black locust tree thorns are poisonous because they produce robin, a fairly strong phytotoxin. Ingesting black locust thorns, bark or leaves may cause colic, weakness, kidney failure, tachycardia and depression. The consumption of a 1/2 pound of leaves or bark can kill a 1,000-pound horse. While a cure exists for black locust tree poisoning, the typical treatment is detoxification.