Photo: Tom ScavoCC BY 4.0via iNaturalistresized / cropped
Black Locust Plant Care
Robinia pseudoacacia L.
Updated · Sources · How we source care data
Robinia pseudoacacia, also known as black locust, is a deciduous tree known for its distinctive pinnately compound leaves and fragrant white flowers. It is popular among plant enthusiasts for its fast growth rate and ability to attract pollinators like bees.nativeTo: North America
Every 7–14 days
Full sun
0–100°F
30–70%
At a glance
How do you care for Black Locust?
Plant Black Locust in full sun (USDA zones 3a–9b) and water a young tree every 7–14 days until it is established. It tolerates temperatures of 0–100°F (-18–38°C). Fertilize it every 8 months during the growing season. The ASPCA lists it as toxic to cats and dogs, so keep it out of reach of pets.
Where Is the Black Locust Native To?
What Is the Black Locust?
Black Locust (Robinia pseudoacacia) belongs to the Fabaceae family within the Robinia genus. Black Locust is native to North America. Black Locust is also known as False Acacia, Yellow Locust, Acacia.
Black Locust displays a fast-growing tree growth habit, reaching up to 30 ft tall with a spread of approximately 20 ft. Black Locust produces showy clusters of fragrant white or pink flowers.
Leaf size: approximately 6 inches.
How Often Should You Water a Black Locust?
Water a young or newly planted Black Locust every 7–14 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established trees mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.
Watering Frequency
Every 7–14 days
Until established; then in dry spells
What Light Does the Black Locust Need?
Black Locust thrives in full sun.
Light Requirement
Full sun
What Temperature and Humidity Does the Black Locust Prefer?
Robinia pseudoacacia tolerates temperatures of 0–100°F. Black Locust prefers humidity levels of 30–70%.
Temperature
0–100°F
Humidity
30–70%
What Soil Mix Works Best for a Black Locust?
Well-draining loamy soil with good fertility. Good drainage is essential for Black Locust to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Black Locust?
Feed Black Locust every 8 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established trees in good soil often need little extra feeding, so let weak growth or pale foliage guide you.
Stop feeding by late summer so new growth can harden before winter.
Fertilizing
Every 8 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
Where Should You Plant a Black Locust?
Choose a spot with full sun and well-draining loamy soil with good fertility. Avoid low spots where water collects after rain.
Black Locust is suited to USDA Zone 3a – 9b.
Plant container-grown or balled-and-burlapped trees in spring or early autumn, setting the root flare at soil level, and water well after planting.
How Far Apart Should You Plant a Black Locust?
Black Locust can spread to about 20 ft (6.1 m) and reach about 30 ft (9 m) tall. Space plants about 20 ft (6.1 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.
Planning a row or hedge? Try the tree spacing calculator.
How Do You Prune a Black Locust?
Prune Black Locust while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.
If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the tree in one year.
How Do You Care for a Black Locust in Winter?
Black Locust is hardy down to USDA zone 3a, so once established it can stay outdoors through winter in that zone and warmer ones.
Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.
Young and container-grown trees need extra protection: roots in a pot freeze much more easily than roots in the ground.
How Do You Propagate a Black Locust?
Black Locust can be propagated through seeds, root cuttings.
Is the Black Locust Toxic to Pets and Children?
Toxic to cats and dogs
Source: ASPCA Animal Poison Control Center plant list, which covers Robinia species (which includes Black Locust). View the ASPCA entry
Toxic to humans and pets if ingested
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Black Locust?
Black Locust is susceptible to aphids, caterpillars, leafhoppers. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Black Locust Need?
Black Locust grows outdoors in USDA Zone 3a – 9b. It survives winters down to planting zone 3a. Black Locust is native to North America.
Hardiness Zone
Zone 3a – 9b
Keep exploring plants
Black Locust is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Robinia genus — compare its care with other Robinia species on PlantoScan.
Robinia is part of the Fabaceae plant family — browse all Fabaceae genera and species.
Black Locust thrives in bright light and direct sun — see other bright-light plants.
Related Plant Care Guides
Closely related plants with similar care requirements:
Sources
- Scientific name & taxonomy: Robinia pseudoacacia L., family Fabaceae (first published in Sp. Pl. : 722 (1753)) — World Flora Online record, IPNI name record, Wikidata.
- Pet toxicity: The ASPCA lists Robinia species (which includes Black Locust) as toxic to cats and dogs. Source: ASPCA Toxic and Non-Toxic Plant List.
- Photo: Tom Scavo, CC BY 4.0, iNaturalist — original.
- Hardiness zone: USDA Zone 3a – 9b, estimated from the plant's typical growing conditions.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
Identify Plants Like the
Black Locust Instantly
Scan any plant with your phone camera and get instant ID, care tips, water and fertilizer reminders, and health checks — all in one app.
Free
to download
iOS & Android
platforms
Light & dark
mode
100,000+
species