Black Locust, Common Robinia, False Acacia, Bastard Acacia, Fragrant White Locust, Locust, Yellow Locust
The Black Locust (Robinia pseudoacacia) is a fast-growing, medium-sized deciduous tree known for its fragrant white flowers, nitrogen-fixing abilities, and adaptability to various soil conditions. It is commonly used for erosion control, windbreaks, and reforestation.
The genus Robinia belongs to the legume family Fabaceae, which includes a diverse range of plants such as peas, beans, lupines, redbuds, and orchid trees.
Native to the Appalachian and Ozark mountain ranges in the eastern United States, Black Locust has been widely naturalized across North America and other continents. It thrives in disturbed habitats, floodplains, forest edges, meadows and fields.
Black Locust is a deciduous, flowering tree with an upright growth habit, a straight trunk, and a narrow crown that becomes more irregular and scraggly with age. It forms dense thickets through root suckering, making it both valuable for soil stabilization and a potential management challenge.
At maturity, Black Locust typically grows 30 to 50 feet (9-15 m) tall with a spread of 20 to 35 feet (6-10 m). It has a rapid growth rate, adding 2 to 4 feet (60-120 cm) per year under optimal conditions. Discover 35 Fast Growing Trees for Small Yards and Large Gardens
This tree spreads by self-seeding and root suckers. Promptly remove suckers unless naturalization is desired.
Although fast-growing, Black Locust is relatively short-lived, typically surviving 60 to 90 years. However, some specimens in Europe have been recorded to live for over 300 years.
Black Locust produces fragrant, pea-like white flowers in hanging racemes 5 to 8 inches (12-20 cm) long in late spring and early summer. Following flowering, the tree develops smooth, flat, purple-brown seed pods that are 2 to 4 inches (5-10 cm) long, containing small kidney-shaped seeds.
The leaves are pinnately compound, 8 to 14 inches (20-35 cm) long, with 7 to 23 ovate to elliptical leaflets. They emerge as a soft green in spring, mature to a blue-green shade in summer, and turn yellow in fall.
The bark is gray-brown with deep furrows and an irregularly ridged texture. Young twigs often have sharp, paired spines at the leaf nodes.
Black Locust is hardy in USDA zones 3-8, demonstrating excellent cold tolerance.
Black Locust is an excellent choice for challenging sites where other trees struggle to thrive. However, caution is advised, as it spreads aggressively through root suckers and prolific seed production, often outcompeting native vegetation and becoming difficult to control in garden settings.
Black Locust provides essential food and habitat for various wildlife species. Its fragrant flowers produce abundant nectar, attracting bees, honeybees, and hummingbirds. It serves as a larval host plant for several butterfly species, including the Silver-Spotted Skipper (Epargyreus clarus), Clouded Sulphur (Colias philodice), and Zarucco Duskywing (Erynnis zarucco).
Black Locust also provides structural habitat for birds, particularly cavity-nesting species such as hairy woodpeckers, downy woodpeckers, northern flickers, and red-bellied woodpeckers. Birds consume its buds and catkins, while its dense foliage offers excellent cover in wetland areas.
Black Locust is somewhat resistant to browsing by deer and rabbits due to its spiny twigs and bitter-tasting foliage. Small mammals and rabbits depend on its seeds and young sprouts for food, especially in winter.
All parts of Black Locust, including the bark, leaves, and seeds, contain toxic compounds harmful to humans, pets, and livestock. The toxins—robin, robitin, and robinine—can cause severe poisoning if ingested, leading to depression, weakness, dilated pupils, vomiting, bloody diarrhea, irregular pulse, and shock. Horses and livestock are particularly vulnerable, with cases of fatal poisoning reported. While the tree does not cause contact dermatitis, ingestion requires immediate medical attention. Fallen leaves and bark pose the highest risk to grazing animals.
Black Locust spreads aggressively through root suckers and abundant seed production, allowing it to dominate disturbed areas. It is considered invasive in prairie and savanna ecosystems, where it shades out native species. Highly adaptable, it thrives in drought, pollution, and high light conditions. It has naturalized in Europe, South Africa, and parts of Asia, and is classified as invasive or regulated in several U.S. states. Its aggressive growth makes it difficult to control once established.
Find where this flowering tree is invasive in the U.S.
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Black Locust is highly drought-tolerant once established. Water regularly during the first two years to promote deep root growth. After establishment, supplemental watering is rarely needed except in extreme drought conditions.
Fertilization is typically unnecessary as Black Locust is a nitrogen-fixing tree that enriches the soil. However, if grown in very poor soils, a balanced fertilizer can be applied in early spring.
Black Locust is susceptible to borers, which can be fatal, and leafminers, which cause browning of foliage. Other potential insect pests include caterpillars, weevils, scale insects, and whiteflies. It may also suffer from fungal diseases such as canker, powdery mildew, leaf spot, root rot in poorly drained soils, and verticillium wilt.
Whether to remove Black Locust (Robinia pseudoacacia) depends on its location and impact. In natural or restored ecosystems, it may outcompete native species due to its aggressive spread through root suckers and prolific seed production. It is considered invasive in many regions. However, in degraded soils or difficult sites, Black Locust can provide erosion control, nitrogen fixation, and timber production. If it is invasive in your area, removal and management may be necessary to prevent further spread.
Black Locust is highly toxic, with all parts of the tree containing harmful compounds such as robinin, robitin, and robinine. If ingested, symptoms in humans and animals may include depression, weakness, dilated pupils, vomiting, diarrhea, weak pulse, and, in severe cases, shock or death. Horses and livestock are particularly vulnerable to poisoning from eating bark, leaves, or seeds.
Hardiness |
3 - 8 |
---|---|
Heat Zones |
3 - 9 |
Climate Zones | 1A, 1B, 2A, 2B, 3A, 3B, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 |
Plant Type | Trees |
Plant Family | Leguminosae |
Common names | Black Locust, Locust |
Exposure | Full Sun |
Season of Interest | Spring (Late), Summer (Early), Fall |
Height | 30' - 50' (9.1m - 15.2m) |
Spread | 20' - 35' (6.1m - 10.7m) |
Maintenance | Average |
Water Needs | Low, Average |
Soil Type | Chalk, Clay, Loam, Sand |
Soil pH | Acid, Alkaline, Neutral |
Soil Drainage | Moist but Well-Drained, Well-Drained |
Characteristics | Fragrant, Showy |
Native Plants | California, United States, Northeast, Pennsylvania, Rhode Island, Vermont, Connecticut, Delaware, Maine, Massachusetts, Maryland, New Hampshire, New Jersey, New York, Illinois, Missouri, Michigan, Kansas, Iowa, Midwest, Indiana, Minnesota, South Dakota, North Dakota, Ohio, Wisconsin, Nebraska, Washington, Oregon, Pacific Northwest, Idaho, Southeast, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, West Virginia, Alabama, Arkansas, Florida, Georgia, Kentucky, Southwest, Texas, Nevada, New Mexico, Oklahoma, Utah, Montana, Rocky Mountains, Wyoming, Colorado |
Tolerance | Drought, Deer, Dry Soil, Clay Soil, Salt |
Attracts | Bees, Birds, Butterflies, Hummingbirds |
Garden Styles | Prairie and Meadow |
Hardiness |
3 - 8 |
---|---|
Heat Zones |
3 - 9 |
Climate Zones | 1A, 1B, 2A, 2B, 3A, 3B, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 |
Plant Type | Trees |
Plant Family | Leguminosae |
Common names | Black Locust, Locust |
Exposure | Full Sun |
Season of Interest | Spring (Late), Summer (Early), Fall |
Height | 30' - 50' (9.1m - 15.2m) |
Spread | 20' - 35' (6.1m - 10.7m) |
Maintenance | Average |
Water Needs | Low, Average |
Soil Type | Chalk, Clay, Loam, Sand |
Soil pH | Acid, Alkaline, Neutral |
Soil Drainage | Moist but Well-Drained, Well-Drained |
Characteristics | Fragrant, Showy |
Native Plants | California, United States, Northeast, Pennsylvania, Rhode Island, Vermont, Connecticut, Delaware, Maine, Massachusetts, Maryland, New Hampshire, New Jersey, New York, Illinois, Missouri, Michigan, Kansas, Iowa, Midwest, Indiana, Minnesota, South Dakota, North Dakota, Ohio, Wisconsin, Nebraska, Washington, Oregon, Pacific Northwest, Idaho, Southeast, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, West Virginia, Alabama, Arkansas, Florida, Georgia, Kentucky, Southwest, Texas, Nevada, New Mexico, Oklahoma, Utah, Montana, Rocky Mountains, Wyoming, Colorado |
Tolerance | Drought, Deer, Dry Soil, Clay Soil, Salt |
Attracts | Bees, Birds, Butterflies, Hummingbirds |
Garden Styles | Prairie and Meadow |
How many Robinia pseudoacacia (Black Locust) do I need for my garden?
Plant | Quantity | |
---|---|---|
Robinia pseudoacacia (Black Locust) | N/A | Buy Plants |
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Becoming a contributing member of Gardenia is easy and can be done in just a few minutes. If you provide us with your name, email address and the payment of a modest $25 annual membership fee, you will become a full member, enabling you to design and save up to 25 of your garden design ideas.
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