Black locust
Robinia pseudoacacia · Fabaceae
📷 Annabell Hormann / korina.info · CC BY-SA 4.0
⚠️ Chiens et chats : écorce et graines contiennent toxines causant troubles digestifs. Humains : ingestion de graines ou écorce dangereuse.
The gardener's calendar
In autumn, ease off feeding and take the chance to clean up around black locust and prepare for winter.
ID card
- Scientific name
- Robinia pseudoacacia
- Family
- Fabaceae
- Type
- Deciduous tree
- Mature height
- 12 to 15 meters
- Flowering
- April to June, white flowers in clusters
- Growth
- Fast
- Hardiness
- Excellent (-25 °C)
- Origin
- North America
- Foliage
- Deciduous, compound and airy
✓ Taxonomy verifiedSource: AI estimate · hardiness: reliability high.
Expert tips
The key tip
Black locust grows very fast but demands well-drained soil and full sun. Water it during the first summer, then it'll manage on its own.
The common mistake
Planting it in compacted or poorly drained soil: growth slows down and the roots rot.
The pro's trick
Install a root barrier (geotextile cloth buried 30 cm deep) if you don't want a forest of seedlings sprouting around it.
Care
Exposure
The black locust requires full sun exposure to grow vigorously and flower generously. It tolerates partially shaded locations but prefers at least 6 hours of direct sunlight per day. It's a sun-loving tree that handles hot, sunny areas well.
Watering
Once established, the black locust is very drought-tolerant thanks to its deep and extensive root system. During the first years, keep the soil moist during dry periods. In normal conditions, water moderately except during persistent heat waves.
Soil
The black locust adapts to almost all soil types: chalky, acidic, poor, or compacted. It thrives even on degraded and neglected terrain. Well-drained soil is preferable to prevent root asphyxiation, but it tolerates difficult conditions well.
Pruning and maintenance
Relatively undemanding in terms of pruning, the black locust naturally forms an elegant tree. Lightly prune young plants to encourage a strong framework. Remove dead or crossing branches in late winter. Be careful of sharp thorns during any work.
Fertilizer
This tree needs no fertilizer at all: as a legume, it fixes nitrogen from the air through its roots. A compost application at the base during the first two years is sufficient for the young plant.
Diseases and pests
The black locust is very hardy and rarely susceptible to diseases. In humid climates, watch for root rot if drainage fails. Grasshoppers and locusts may occasionally defoliate it, but without serious consequences. Its dense wood resists fungal attacks well.
Did you know?
Introduced from North America to Europe in the 17th century, the black locust quickly conquered the continent: its qualities (hard wood, resistance, fast growth) made it a precious tree for forestry. It is now considered naturalized in Europe and plays an important ecological role, particularly in fixing nitrogen and regenerating degraded soils.
Where to buy it
Best planted in autumn so the roots settle in before summer, or in early spring once the frost has passed. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, October, November.
Add this plant to my garden →Plants from the same family
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- Common broomCytisus scoparius
- Common PeaLathyrus oleraceus
- Honey locustGleditsia triacanthos
- Hairy greenweedGenista pilosa
- Strawberry cloverTrifolium fragiferum
Tips generated and checked by Viridia — adapt them to your local climate.