Robinia pseudoacacia 'Tortuosa'
Common Name: black locust
Type: Tree
Family: Fabaceae
Zone: 4 to 8
Height: 10.00 to 15.00 feet
Spread: 10.00 to 15.00 feet
Bloom Time: May
Bloom Description: White
Sun: Full sun to part shade
Water: Dry to medium
Maintenance: Medium
Flower: Showy, Fragrant
Other: Thorns
Tolerate: Deer, Drought, Clay Soil, Air Pollution

Culture

Grow in average, dry to medium, well-drained soils in full sun. Tolerates some light shade, but avoid shady locations. Tolerates a wide range of soils including sandy or nearly barren ones. Best performance is in moist, organically rich loams. Good drought tolerance. Fixes nitrogen. Avoid pruning in spring when it tends to bleed.

Noteworthy Characteristics

Robinia pseudoacacia, commonly called black locust, is medium sized, suckering, deciduous tree that typically grows to 30-50’ (less frequently to 80’) tall. Although originally native to the Allegheny Mountains, it has escaped gardens and naturalized over time to cover much of the United States and southern Canada plus parts of Europe, Asia and South America. At its best, it will grow as a broadly columnar single trunk tree with a narrow oblong crown. It also will grow in suckering thickets. It is noted for its attractive compound leaves and pendant racemes of pea-like flowers. Branches are usually armed with short paired spines (to 1.25” long). Pinnate dark blue-green leaves, with each leaf having up to 23 lance-shaped to ovate leaflets. Leaves turn uneventful yellow in fall. Fragrant wisteria-like white flowers in pendant racemes (to 8” long) bloom in late spring. Bees are attracted to the flowers. Flowers are followed by smooth, flat, purple-brown seed pods (to 4-5” long). This species is also commonly called common locust, yellow locust, white locust, green locust, pea flower locust and false acacia.

Genus name honors Jean Robin (1550-1629), of Paris, gardener to Henri IV and Louis XIII of France, who received new plants from Canada.

Specific epithet means false acacia.

‘Tortuosa’ is a slow-growing, deciduous black locust that is noted for its compact size and twisted branching. It may grow over time to as much as 40’ tall and 25’ wide, but is more often seen in gardens growing only to 10-15’ tall. Pinnate green leaves are attractive during the growing season. No fall color. Plants may not produce the racemes of fragrant flowers in May and the resulting seed pods typical of the species, but, if they do flower, the racemes will be much smaller with fewer flowers. Small spines may appear on the branches. See Robinia pseudoacacia ‘Lace Lady’ TWISTY BABY for another compact black locust with contorted branching.

Problems

Black locust is generally considered to be a very easy-to-grow tree. It thrives in many difficult growing conditions. It is susceptible to locust borer (often fatal) and locust leaf miner (browns foliage). Other insect problems include caterpillars, weevils, scale and whiteflies. Possible disease problems include canker, powdery mildew, leaf spots, wood rots and verticillium wilt.

Garden Uses

Compact tree is effective as a small accent for the landscape. Twisted branching can be attractive in winter.