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Summary This account presents information on all aspects of the biology of R obinia pseudoacacia L. that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the B iological F lora of the B ritish I sles : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, and history and conservation. R obinia pseudoacacia , false acacia or black locust, is a deciduous, broad‐leaved tree native to N orth A merica. The medium‐sized, fast‐growing tree is armed with spines, and extensively suckering. It has become naturalized in grassland, semi‐natural woodlands and urban habitats. The tree is common in the south of the B ritish I sles and in many other regions of E urope. R obinia pseudoacacia is a light‐demanding pioneer species, which occurs primarily in disturbed sites on fertile to poor soils. The tree does not tolerate wet or compacted soils. In contrast to its native range, where it rapidly colonizes forest gaps and is replaced after 15–30 years by more competitive tree species, populations in the secondary range can persist for a longer time, probably due to release from natural enemies. R obinia pseudoacacia reproduces sexually, and asexually by underground runners. Disturbance favours clonal growth and leads to an increase in the number of ramets. Mechanical stem damage and fires also lead to increased clonal recruitment. The tree benefits from di‐nitrogen fixation associated with symbiotic rhizobia in root nodules. Estimated symbiotic nitrogen fixation rates range widely from 23 to 300 kg ha −1 year −1 . The nitrogen becomes available to other plants mainly by the rapid decay of nitrogen‐rich leaves. R obinia pseudoacacia is host to a wide range of fungi both in the native and introduced ranges. Megaherbivores are of minor significance in E urope but browsing by ungulates occurs in the native range. Among insects, the N orth A merican black locust gall midge ( O bolodiplosis robiniae ) is specific to R obinia and is spreading rapidly throughout E urope. In parts of E urope, R obinia pseudoacacia is considered an invasive non‐indigenous plant and the tree is controlled. Negative impacts include shading and changes of soil conditions as a result of nitrogen fixation.