Searching...
Plant Search
Search for any plant to learn how to grow it.
Black Locust
Robinia pseudoacacia
treeBlack locust is a fast-growing, deciduous hardwood tree native to eastern North America, known for its fragrant white flower clusters and nitrogen-fixing abilities. It reaches 40-60 feet tall and develops a dense, spreading crown with compound leaves. The wood is exceptionally hard and decay-resistant, making it valuable for timber, fence posts, and ornamental use.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in USDA zones 3-9; most vigorous in zones 4-8
Sign up to see your zone highlighted.
Growth Stages
Seedling/Nursery Stage
1-2 yearsYoung trees with thin stems and compound leaves consisting of 7-21 leaflets; may produce thorns on new growth
Keep soil consistently moist but not waterlogged. Protect from competing weeds. Stake if necessary in windy locations. Remove competing leaders to develop single main trunk.
Establishment Phase
2-3 yearsTree develops stronger branching structure and deeper root system; 10-25 feet tall; bark begins to develop furrows
Continue regular watering during dry periods. Prune lower branches to develop clear trunk if desired. Thin competing leaders early.
Pre-Flowering
2-3 yearsTree reaches 20-35 feet; crown fills out with dense foliage; first flower buds may form
Minimal pruning needed. Remove diseased or crossing branches. Allow natural branching unless timber form desired. Monitor for pest damage.
Flowering
3-4 weeksFragrant white flower clusters (racemes) appear in late spring, typically May-June; flowers attract pollinators
No special care needed. Flowering generally indicates tree vigor. Some trees may produce seedpods; remove if self-seeding is problematic.
Mature Tree
30+ yearsTree reaches full size (40-60+ feet); produces abundant seed pods in summer; wood hardens and becomes exceptionally durable
Minimal maintenance. Remove dead or diseased branches. Control suckering if near structures or gardens. Thin seed pods if prolific self-seeding is undesired.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
-
Avoid wounding trees; remove infested branches. Sawdust-like frass indicates infestation. Maintain tree vigor.
-
Remove and destroy infested branches. Prevent tree stress through proper watering. Paint large wounds to seal.
-
Usually causes cosmetic damage only. Remove heavily infested foliage. Maintain tree health.
-
Hand-pick bags in winter. Prune infested branches. Bacillus thuringiensis (Bt) spray in early season if severe.
-
Hand-pick or use Japanese beetle traps away from tree. Rarely causes significant damage. Avoid systemic pesticides.
Uses
Durable Timber & Fence Posts
HouseholdBlack locust wood is one of the hardest and most decay-resistant domestic woods, naturally containing compounds that resist rot and pests. It is prized for fence posts, railroad ties, playground equipment, and flooring. [source]
Edible Flowers
CulinaryThe fragrant white flowers are edible with a sweet, vanilla-like flavor and can be used in fritters, salads, syrups, and herbal teas. Flowers are harvested in late spring when fully open. [source]
Traditional Herbal Remedy
MedicinalHistorically used in folk medicine for digestive issues, coughs, and as a tonic. Bark and roots contain compounds with potential antimicrobial properties, though modern scientific evidence is limited. [source]
Nitrogen Fixation & Ecosystem Value
WildlifeBlack locust forms symbiotic relationships with nitrogen-fixing bacteria in root nodules, enriching soil and improving conditions for other plants. It provides nectar for pollinators and seeds for birds. [source]
Honey & Apiary Value
CraftBlack locust is an excellent nectar source for honeybees, producing pale, mild-flavored honey prized for its delicate taste and slow crystallization rate. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Black locust is harvested as timber rather than as a food crop. Lumber can be harvested once trees reach 20-30 years old and 12+ inches diameter at breast height. Fell trees in dormant season for best wood quality. Flowers can be harvested in late spring for culinary/craft uses (fritters, tea, syrup) by clipping fresh racemes. Seed pods can be collected in fall when dried and brown.
Fun Facts
- 🌱 Black locust is not a true locust (which are insects); the name comes from early colonists' confusion with carob trees called 'locust' in the Middle East.
- 🌱 A single black locust tree can live 100+ years, and its wood can remain structurally sound for 200+ years in outdoor conditions, making fence posts functional for multiple decades.
- 🌱 Black locust was one of the first North American trees planted extensively in Europe during the 17th century and has become naturalized in many parts of the world.
Want to save this plant and get personalized recommendations?
Sign up to add plants to your list, see your growing zone highlighted, and get planting timelines based on your frost dates.