Black locust

Robinia pseudoacacia

Fast-growing North American leguminous tree. Wood is one of the most rot-resistant timbers in temperate climates — fence posts last 50+ years. Heavy nitrogen fixer.

Hardiness ratings

Black locust hardiness across the four zone systems
SystemRatingTemperature rangeHow to read it
USDA hardiness zone Zone 3–8 −40 °C to −6.7 °C Plant tolerates down to this zone
RHS hardiness rating H7 down to −20 °C Plant needs at least this level of cold tolerance
Canadian plant hardiness zone Zone 3–8 −34 °C to −1 °C Plant tolerates down to this zone
Australian (ANBG) zone Zone 1–4 −15 °C to 5 °C Plant tolerates down to this zone

Growing notes

  • Suckering — once established, sends up shoots from the roots that can be difficult to remove
  • Excellent firewood and exceptionally durable timber for posts and outdoor structures
  • All parts except the flowers are toxic if eaten — bark especially
  • White flower racemes in late spring are a major nectar source — basis of European acacia honey

Pet caution: Black locust is listed as potentially harmful to cats and/or dogs. Keep pets from grazing on it, and contact a vet if you suspect your animal has eaten some.

Categories

Related plants

Cross-check Black locust against your zones

Reference

Black locust on Wikipedia