Black locust
Robinia pseudoacacia, family Fabaceae
A tall, fragrant-flowered tree native to eastern North America
Black locust is a medium-sized deciduous tree from the legume family, known for its upright trunk, compound blue-green leaves, and drooping clusters of fragrant cream-white flowers. Native to the eastern United States, it has spread widely and is valued for its fast growth, soil enrichment, and timber, but is also considered invasive in some areas.
- Native to the Appalachian and Ozark regions of the United States
- Produces fragrant, creamy white flowers in late spring
- Introduced to Europe by Jean Robin around 1600
- Fixes nitrogen and improves poor soils
- Can become invasive and form dense thickets
What does Black locust look like?
Black locust is a tall, upright tree reaching 12–30 metres, with deeply furrowed dark bark and zig-zag branches. Its leaves are compound, blue-green above and lighter below, made up of 9–19 rounded leaflets. In late spring, it produces drooping clusters of creamy white, strongly scented flowers, sometimes pink or purple, each about 2.5 cm wide. Young trees may have pairs of sharp, dark purple spines at the base of the leaves. The fruit is a flat, pea-like pod containing several seeds.
Where does Black locust come from?
Black locust is native to the eastern United States, mainly the Appalachian Mountains and Ozark Plateau. It was first described by British colonists in Jamestown in 1607 and named for its resemblance to the Old World locust tree. Jean Robin introduced it to France around 1600, and it spread across Europe and beyond. Its rapid growth and ability to fix nitrogen made it useful for stabilizing soil and reclaiming land, especially in Hungary and other parts of Europe.
When and how Black locust blooms
Black locust flowers open in May or June, after the leaves have appeared. The tree grows best in sunny, disturbed areas with dry or sandy soil. It reproduces by both seeds and root suckers, forming colonies that can crowd out other plants. Seeds have a tough coat and may need scarification to germinate well. The tree is hardy and spreads easily, making it both useful and sometimes invasive.
How Black locust is used
People value black locust for its fragrant flowers, which attract pollinators and are sometimes used in home gardens. Its wood is durable and has been used for building since colonial times. The tree improves poor soils by fixing nitrogen, and has been planted for erosion control. Some traditional medicines use parts of the tree, but it is also known to be poisonous.
Kinds of Black locust
There are several cultivated forms, including a hybrid with pink flowers called Robinier de Descaines. Black locust is sometimes confused with honey locust, but differs in its paired short spines and broader leaflets. Some trees are densely prickly, while others lack spines. The species is variable in spine presence and flower color.
What Black locust means
Black locust has played a role in European history, especially in Hungary, where it was planted for military and environmental reasons. The oldest known trees in Europe are in Paris, linked to the botanist Jean Robin. It is valued for its timber and soil improvement, but is also listed as invasive in some countries. The tree is not closely related to true acacias, despite the common name 'false acacia'.
Questions people ask about Black locust
Where does black locust come from?
Black locust is native to the eastern United States, especially the Appalachian Mountains and Ozark Plateau. It has since spread widely through planting and naturalization in many parts of the world.
What does the black locust flower look like?
The flowers are creamy white, sometimes pink or purple, and grow in loose, drooping clusters. Each flower is about 2.5 cm wide and has a strong, sweet scent.
Is black locust used for anything?
Black locust is valued for its timber, fragrant flowers, and ability to improve soil by fixing nitrogen. It has also been used in traditional medicine, though parts of the tree are poisonous.
Why is it called 'false acacia'?
The name 'false acacia' comes from its scientific name, Robinia pseudoacacia. Although its leaves and spines resemble those of acacia trees, it is not closely related to true acacias.
Is black locust considered invasive?
Yes, in many regions outside its native range, black locust spreads quickly by root suckers and seeds, forming dense thickets that can crowd out other plants.
Good reading and sources
- Encyclopaedia BritannicaArticle
- IUCN Red List of Threatened SpeciesIUCN Red List, Article
- Plants of the World OnlineRoyal Botanic Gardens, Kew, Plant database
- Where it has been recordedGBIF, Plant database
- Sightings and photos by naturalistsiNaturalist, Plant database
- Robinia pseudoacacia on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Robinia pseudoacacia", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). Phool rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes. It is not medical or foraging advice: many flowers are poisonous, and traditional uses are reported, not recommended. If something is wrong, tell us. Last refreshed 2026-10-03.
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