Now listed as an invasive plant in Minnesota, the black locust is tolerant of most site conditions. These trees are among the Fabaceae family of trees and do have nitrogen fixing atributes. This is the reason they were planted in the first place, they have now escaped and can spread vigorously. They can spread by means of seed distrobution or by root suckers. If you have a black locust growing nearby, you have probably seen these root suckers in your yard.