Black locust is a ‘nearly native’ tree. Originally from the eastern US, it is cold hardy and produces many seeds, and is now found across southern Canada where it has naturalized. An attractive tree, it has large hanging clusters of white flowers; some hybrid cultivars are planted in Montréal that have purple or pink flowers too. The flowers and fruits look like those of pea plants, and indeed this tree is in the bean family, Fabaceae. Like all the other members of Fabaceae, black locust can make use of atmospheric nitrogen, an element that is often in short supply in the soil. It does so with the help of symbiotic bacteria that live in its roots. This helps to make locusts and other Fabaceae trees better suited for success in otherwise difficult sites for establishing trees. However, be warned if you chose to plant one—this tree is thorny, has a large root system that could interfere with nearby infrastructure, and will make many, many baby trees! It is not much of a threat to native woodlands though, as it cannot grow in the shade of other trees.