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Robinia pseudoacacia L.
Fabaceae (Pea Family)
Synonym(s): Robinia pseudoacacia f. inermis, Robinia pseudoacacia var. pyramidalis, Robinia pseudoacacia var. rectissima
USDA Symbol: rops
USDA Native Status: L48 (N), CAN (I)
The largest representative of a mostly shrubby genus, black locusts become burly, pictureque mature trees 30-50 ft. or sometimes 70 ft., in height. Branching tends to fork and become crooked and limby. Small branches and twigs with spines, especially at the base of leaves. Leaves divided into ovate to oblong leaflets up to 2 inches long and 1 inch wide, rounded at the ends and with smooth margins. Blue-green, feathery, pinnately-compound foliage contrasts well with the deciduous tree dark, furrowed bark. Fragrant, white, pea-like blossoms hang in pendulous clusters. Flowers appearing in April and May. Fruit a flat, straight to slightly curved pod up to 5 inches long.
British colonists at Jamestown discovered this species in 1607 and named it for its resemblance to the Carob or Old World Locust (Ceratonia siliqua L.). Posts of this durable timber served as cornerposts for the colonists' first homes. Because this species is well-adapted to establishment in very poor soil, it has been widely used for land reclamation projects.
The eagerness of Robinia pseudoacacia to establish just about anywhere has a dark side; Black locust is often considered an invasive species and a garden thug because it spreads very rapidly by root sprouts and by the copious seeds it produces. Its wood, renowned for its toughness, belies its habit of shedding branches in high winds. Finally, its small thorns can surprise anyone attempting to work in or around the tree, especially young trees and new branches. This species and its various cultivars and hybrids should be rejected for most landscape uses because of the tree's many bad habits.
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Plant CharacteristicsDuration: Perennial
Leaf Retention: Deciduous
Leaf Arrangement: Alternate
Leaf Complexity: Pinnate
Fruit Type: Legume
Size Notes: Up to about 70 feet tall.
Bloom InformationBloom Color: White
Bloom Time: Apr , May , Jun
DistributionUSA: AL , AR , CA , CO , CT , DC , DE , FL , GA , IA , ID , IL , IN , KS , KY , LA , MA , MD , ME , MI , MN , MO , MS , MT , NC , ND , NE , NH , NJ , NM , NV , NY , OH , OK , OR , PA , RI , SC , SD , TN , TX , UT , VA , VT , WA , WI , WV , WY
Canada: BC , NB , NS , ON , PE , QC
Native Distribution: GA to LA & AR, n. to PA, WV, s. IN, s. IL, LA & e. OK; naturalized elsewhere
Native Habitat: Woods; thickets; fence rows
Growing ConditionsWater Use: Medium
Light Requirement: Sun
Soil Moisture: Dry , Moist
Soil pH: Circumneutral (pH 6.8-7.2)
CaCO3 Tolerance: High
Soil Description: Moist, rich to dry, rocky soils.
BenefitUse Ornamental: Black Locust is widely planted for ornament and shelterbelts. It is also used for erosion control, particularly on strip-mined areas. Although it grows rapidly and spreads by sprouts like a weed, it is short-lived.
Use Wildlife: Flowers are a favorite of honeybees and hummingbirds.
Use Other: Virginia Indians made bows from the wood and apparently planted the trees eastward.
Warning: This species naturalizes easily and is considered an invasive weed in many of its non-native areas of establishment. Its brittle branches (subject to breaking in winds), vicious thorns, rampant root sprouts and copious seeding make this species a garden thug.
Conspicuous Flowers: yes
Fragrant Flowers: yes
Interesting Foliage: yes
Attracts: Birds , Butterflies , Hummingbirds
Nectar Source: yes
Value to Beneficial InsectsSpecial Value to Native Bees
Special Value to Honey Bees
This information was provided by the Pollinator Program at The Xerces Society for Invertebrate Conservation.
PropagationDescription: Propagate by seed, spring root cuttings or dormant sucker divisions. Cuttings should be stored in cool, dry sand for three weeks before planting.
Seed Treatment: Mechanical or acid scarification or a hot water soak is necessary due to impermeable seed coats.
Commercially Avail: yes
Find Seed or Plants
View propagation protocol from Native Plants Network.
National Wetland Indicator Status
BibliographyBibref 354 - Native & Naturalized Woody Plants of Austin & the Hill Country (1981) Lynch, D.
Bibref 248 - Texas Wildflowers: A Field Guide (1984) Loughmiller, C. & L. Loughmiller
Bibref 297 - Trees of Central Texas (1984) Vines, Robert A.
Search More Titles in Bibliography
Additional resourcesUSDA: Find Robinia pseudoacacia in USDA Plants
FNA: Find Robinia pseudoacacia in the Flora of North America (if available)
Google: Search Google for Robinia pseudoacacia
MetadataRecord Modified: 2022-05-03
Research By: TWC Staff