Robinia pseudoacacia L.

Black locust

Black locust is native to the southeastern United States. It has been planted and become naturalized in temperate parts of Europe, Africa, Asia, Australia, and North America. In some areas it has become common to invasive. They spread by seed or by producing extensive suckers, creating large clonal colonies, and require plenty of sun. There are many cultivars.

Plants: These deciduous trees reach 40–100′ (12–30 m), with trunks up to 2–4′ (60–121 cm) in diameter. Bark is light brown or dark gray brown, ridged and furrowed, with bits of red or orange visible in grooves. Young trees are spiny, but mature trees often lack spines. Branches are zigzagged, rounded or grooved, changing from silvery to pale green, then to reddish or brown.

Leaves: Leaves are alternate, odd pinnate, 6–14″ (15–35 cm) long, divided into 7 to 23 small leaflets. Leaflets are elliptic, and dark blue-green, lighter beneath. Dark purple prickers develop from stipules at leaf bases, ¼–¾″ (6.3–20 mm) long, each with a flared base and sharp tip.

Flowers: Large, beautiful hanging racemes of scented flowers, 4–8″ (10–20 cm) long. The flower clusters resemble wisteria. Flowers are creamy white, or rarely pink or purple, each about 1″ (2.5 cm) in size. The calyx at the base of each flower is reddish-purple. They appear in May-June and last for only 7 to 10 days.

Fruits: Flat, smooth, dark orange-brown pea-like pods 2–4″ (5–10 cm) long, with 4-8 kidney-shaped seeds. They persist all winter.

Habitats: Thickets, on clay banks, in waste areas, or along fence rows.

Edibility: Poisonous Bark, young leaves, and seeds are poisonous if eaten. Poisoning symptoms include depres­sion, weakness, dilated pupils, vomiting, bloody diarrhea, weak pulse, coldness of arms and legs, paleness, and shock. Flowers, however, are edible. After soaking in warm water for several minutes to remove dirt, flowers can be battered and deep fried, or chopped and added to muffin or pancake batter.

Online References:

Older scientific or horticultural names

Robinia pseudoacacia description by Thomas H. Kent, not updated.

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