Is it a good tree for a small garden?

No, it grows very large and spreads aggressively via suckers.

Does it need fertilizer?

No, it fixes its own nitrogen and thrives in poor soils.

Plant guide

Black Locust.

Robinia pseudoacacia

Pronounced roh-BIN-ee-uh soo-doh-uh-KAY-see-uh

Also known as Black Locust, False Acacia, False-acacia

The black locust is a hardy, fast growing tree known for its fragrant, pea like flowers that bloom in late spring. It is a tough plant that thrives in various soil conditions and is often used for erosion control. You will love how its delicate, fern like foliage adds a soft texture to your landscape.

At a glance

Care level: Easy
Plant type: Deciduous tree
Light: Full sun
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: 30 to 50 feet
Growth rate: Fast
Hardiness: USDA 3 to 8
Bloom time: Late spring to early summer

Care

Plant this tree in a spot with plenty of sun to encourage the best flowering. Keep an eye out for suckers spreading from the roots, as this tree can be quite vigorous. It is very drought tolerant once established, so you won't need to fuss over it much.

Watering: Water deeply during the first year to help roots establish, then rely on rainfall.
Feeding: Usually does not require fertilizer as it fixes its own nitrogen.
Pruning: Prune in late winter while dormant to remove dead wood or shape the canopy.
Repotting: This is a large tree meant for outdoor planting and is not suitable for containers.
Soil: Well draining soil
Soil pH: 6.0 to 8.0
Temperature: -35 to 35°C
Humidity: 30 to 70%
Drought tolerance: High
Lifespan: Perennial, typically 50 to 100 years
Fragrance: Strong
Deer and rabbits: Moderate

Safety

People: Most parts of this plant, especially the bark, leaves and seeds, are toxic if eaten, as they contain lectins and robinin. The flowers are the exception and are traditionally eaten cooked.
Pets: This plant is toxic to cats and dogs if ingested, as it contains proteins that can cause gastrointestinal distress.
Children: Keep children away from the seed pods, which can be mistaken for edible legumes.
Contact allergens: The sharp thorns can cause mechanical injury and skin irritation.
Airborne allergens: The pollen may cause mild respiratory irritation in sensitive individuals.
Edibility: The bark, leaves, and seeds are toxic to humans and animals if ingested.

How to identify it

Compound leaves with oval leaflets
Fragrant white drooping flower clusters
Deeply furrowed dark brown bark
Sharp paired thorns on branches

Height: 12 to 25m
Spread: 6 to 15m
Leaves: green, blue-green, deciduous
Flowers: white, 1 to 2cm
Fruit: brown, Autumn

Problems to watch for

Locust borer · Larvae tunnel into the trunk, weakening the wood.
Leaf miner · Larvae feed between leaf surfaces, causing browning.

By symptom

Plant problems by symptom

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Growing it

Propagation: seed, cuttings, root suckers
When to plant: spring, autumn
Overwintering: No special care is needed as it is very cold hardy. Ensure the area is well drained to prevent root rot during wet winters.
In containers: Not suitable for containers due to its massive size and extensive root system.

Seed

1. Scarify the hard seed coat with sandpaper.
2. Soak seeds in warm water for 24 hours.
3. Plant in well draining soil.

Plant in areas where its aggressive root suckering will not interfere with other garden beds.

Grows well with

Wild Indigo · Both plants thrive in similar sunny, well drained conditions.
Switchgrass · It provides a nice textural contrast to the locust foliage.

Similar species

Honey Locust · It has similar pinnate leaves but different fruit and flower structures.

Science

Family: Fabaceae
Genus: Robinia
Order: Fabales
Class: Magnoliopsida
Native range: Eastern United States
Conservation: It is considered an invasive species in many regions outside its native range.

It colonizes disturbed areas quickly and improves soil fertility through nitrogen fixation.

Value to wildlife: nectar source, honey production
Pollinators: bees, butterflies
Uses: ornamental tree, erosion control, honey production, timber

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 8/9
Temperature: 5/9
Moisture: 4/9
Nutrients: 3/9

Taxonomy resolved against GBIF.

Questions people ask

Is it a good tree for a small garden?: No, it grows very large and spreads aggressively via suckers.
Does it need fertilizer?: No, it fixes its own nitrogen and thrives in poor soils.

Where the name comes from

Named for Jean Robin, who introduced the tree to Europe, and pseudoacacia for its resemblance to the acacia genus.

Good to know

It is a member of the pea family and fixes nitrogen in the soil.
The flowers are highly fragrant and edible when fried in batter.
It grows very quickly but has relatively brittle wood.

Also in

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This guide was generated with AI on October 19, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.