Tree · Fabaceae family
black locust
Robinia pseudoacacia
In short a 10-second read
Black locust (tree) grows to 15–25 m tall and 6–20 m wide when mature. It grows best in full sun, in dry to average soil. It flowers in May–June; the flowers are white. Hardy to −34 °C.
× spread 6–20 m
Where to plant
Sun, soil, frost.
It grows best in full sun, in dry to average soil. Hardy to −34 °C.
Sun
Elsewhere it will grow less well.
Soil and water
dry to average · watering: little
Soil: sandy, loamy, gravelly
Frost
It copes with a normal winter outdoors.
How much space it takes
Mature size.
The mature plant next to a person (175 cm).
Next to a person
Reaches maturity in about 20–50 years. The final size depends on the cultivar and the spot — we give the range from smallest to largest.
Calendar
What to do and when.
Months for Central Europe. The line shows the current month.
The year at a glance
Flowers
May–June · white
Pruning
No pruning needed — just remove dead or damaged parts.
Planting
container plant: October–April; bare-root: October–March; root-balled: October–March
Winter protection
not needed
Overwintering
It copes with winter on its own.
It overwinters outdoors without protection, hardy to −34 °C.
- Needs no protection
- Hardy to −34 °C
- Deciduous — bare in winter
Frequently asked
Quick answers.
When does black locust flower?
In May–June; the flowers are white.
Does black locust tolerate shade?
No, it needs full sun.
How much space does black locust need?
At maturity 6–20 m wide and 15–25 m tall; recommended spacing 600 cm.
Does black locust survive winter outdoors?
Yes, without protection, hardy to −34 °C.
Toxicity
Where the data comes from
The data is indicative — we are still comparing it with further sources. Last checked 18 October 2026.
Show sources (17)
- Slov-lex — nariadenie vlády SR č. 449/2019 Z. z.
- Pergl J. et al. (2016) Black, Grey and Watch Lists of alien species in the Czech Republic, NeoBiota 28 — Appendix
- Nehring S. et al. (2013) BfN-Skripten 352 — Schwarze/Graue Liste
- GBIF — Robinia pseudoacacia
- Okrasné škôlky (SK) — Listnaté stromy
- NC State Extension Plant Toolbox
- Van den Berk
- GBIF Backbone Taxonomy (species/match)
- Wikipedia (EN)
- RHS - Robinia pseudoacacia
- RHS - Shrubs and trees: light pruning
- RHS - Trees and shrubs: planting
- Clemson HGIC - Planting Trees Correctly
- RHS - How to grow trees
- Tox Info Suisse — Giftige Garten- und Wildpflanzen
- BfR / GIZ — Liste giftiger Pflanzenarten
- Giftzentrale Bonn (GIZ Bonn)
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