Styphnolobium affine aka Texas Sophora

Styphnolobium affine is a deciduous shrub or small tree. It belongs to the bean family, Fabaceae. Common names include Texas sophora and Eve’s necklace. Its native range covers Texas, Oklahoma, Arkansas, and Louisiana. It grows near creeks, in woods, and across open ground. Wild plants often grow in limestone soils. Some develop a thin, sprawling form that looks vine-like.

In gardens, expect heights of about 15–20 feet [4.6–6.1 metres]. Some trees reach 35 feet [10.7 metres], but most stay shorter. The spread reaches 10–20 feet [3–6.1 metres]. Several trunks support an upright, oval or uneven crown. Low branches may need pruning beside paths or driveways. The thin, red-brown bark has scales and damages easily. Smooth stems bear alternate, pinnate leaves with a glossy surface. Each leaf has six to eight pairs of oval leaflets. The dark green leaves feel leathery and fall in autumn.

Fragrant pink flowers open from early to mid-spring. The bloom lasts about two weeks. Small flowers form racemes about 0.5 feet [0.15 metres] long. Their loose clusters recall wisteria blooms. Pollinators visit the flowers, and birds nest among the branches. Black legumes form from summer into fall. Narrow sections between seeds give each pod a beaded shape. These pods explain the name Eve’s necklace. They stay on the tree through winter and add interest.

Grow this tree in full sun or partial shade. Full sun brings more flowers and tends to keep trees shorter. It tolerates heat and drought well. Clay, loam, and sand suit it when water drains freely. It also accepts acidic, neutral, and alkaline soils. Poor drainage can cause chlorosis in the leaves. The listed hardiness range is USDA zones 7–9. Growth is moderate, and maintenance needs are also moderate. Use it beneath taller trees or behind a border. It also works as a specimen or container plant. In colder places, containers can move indoors for winter.

No serious insect or disease problems are reported. The tree also resists deer. Take care around its seeds and flowers, which poison humans. The source rates poisoning severity as low, but lists serious symptoms. Eating seeds can cause vomiting, diarrhea, delirium, or coma. These parts should not be treated as food. The evidence does not establish whether the plant harms pets.