Leucaena retusa aka Littleleaf Leadtree

Leucaena retusa is a large shrub or small tree. It belongs to Fabaceae, the pea and bean family. Its native range runs from the south-central United States into northeastern Mexico. It grows in desert or dry shrubland habitats. The RHS also lists the name Caudoleucaena retusa as a synonym. This species is not native to Britain or Ireland.

The crown spreads broadly, giving the plant a wide outline. Plants can reach 25 feet [7.6 m], though most remain smaller. The available evidence gives no narrower range for garden plants. The bark is smooth and gray-brown. Slender twigs range from green to reddish brown. They have a somewhat angled shape and may bear fine hairs. The small buds have a wedge shape.

Leaves grow alternately along the stems, rather than in opposite pairs. Each leaf is bipinnate, with two levels of branching. Whole leaves measure about 0.25–0.5 feet [0.08–0.15 m] long. Most have three pairs of main divisions. Each division bears 10–15 pairs of small leaflets. These leaflets range from egg-shaped to narrow and lance-shaped. Their edges are smooth, with no teeth. Each small leaflet measures about 0.04 feet [0.013 m] long. The upper surface ranges from green to blue-green. The underside has a paler shade.

Many small flowers gather into dense, round heads. Their color ranges from yellow to white, and they have a scent. Each head can span about 0.125 feet [0.038 m]. It sits on a stalk about 0.17–0.25 feet [0.05–0.08 m] long. Virginia Tech records flowers from April through October, following rain. It describes the species as monoecious, with both sexes on one plant. The fruit is a straight, flat, reddish-brown pod. Pods can reach about 0.67 feet [0.20 m] long. They ripen from spring through fall.

The broad crown, divided leaves, and round flower heads define its appearance. Its native habitat gives context for its link with dry landscapes. The supplied sources do not set out garden watering needs. They also give no planting guidance, soil needs, or hardiness limits. No supported details cover pests, diseases, food uses, or toxicity. Those gaps do not establish that any plant part is safe to eat.