Common Names: Black locust, false acacia
A medium-sized deciduous tree native to the southeastern United States, but it has been widely planted and naturalized elsewhere in temperate North America and is considered an invasive species in Connecticut. It reaches a typical height of 12 to 30 m with a diameter of 0.6 to 1.2 m. It is a very upright tree with a straight trunk and narrow crown which grows scraggly with age. The dark blue-green compound leaves with a contrasting lighter underside. Young trees are often spiny, however, mature trees often lack spines. In the early summer black locust flowers; the flowers are large and appear in large, intensely fragrant (reminiscent of orange blossoms), clusters. The leaflets fold together in wet weather and at night (nyctinasty) as some change of position at night is a habit of the entire leguminous family. Although similar in general appearance to the honey locust, it lacks that tree's characteristic long branched thorns on the trunk, instead having the pairs of short prickles at the base of each leaf; the leaflets are also much broader then honey locust. Black locust is a shade intolerant species and therefore is typical of young woodlands and disturbed areas where sunlight is plentiful and the soil is dry. In this sense, black locust can often grow as a weed tree. It also often spreads by underground shoots or suckers which contribute to the weedy character of this species.