Baptisia australis aka Blue False Indigo

Baptisia australis is known as blue false indigo. This herbaceous perennial belongs to the bean family, Fabaceae. It is native to the central and eastern United States. It grows in woods, thickets, and along stream banks. Its range includes Pennsylvania south to North Carolina and Tennessee. The plant forms upright clumps with a rounded leaf mound. Garden plants reach 3–4 feet (0.9–1.2 metres) tall. They spread 2–4 feet (0.6–1.2 metres) wide. RHS lists heights up to about 5 feet (1.5 metres).

The blue-green leaves have three leaflets, much like clover leaves. Each leaflet has smooth edges and can reach two inches long. The leaves grow alternately along the stems. They stay attractive through the growing season, then blacken when dry. Blue to violet flowers rise above the leaf mound. Their pea-like shape gives the spikes a lupin-like look. Flowering falls in May and June. Puffy seed pods follow the flowers and ripen black in late summer. They reach about two and a half inches long. Loose seeds rattle inside the dry pods.

Full sun gives the best bloom and a firmer shape. The plant also grows in part shade. Shade can make stems stretch and fall over. It needs soil that drains well, from dry to moderately moist. It tolerates poor soil, clay, and shallow, rocky ground. Deep roots help established plants cope with drought. Those roots also make moving mature clumps hard. Plants raised from seed can take several years to settle in. Leave established clumps in place where possible. Sources list USDA zones 3–8 and 4–9. RHS gives it a UK hardiness rating of H7.

Use it in borders, cottage gardens, meadows, or native plant gardens. Single plants and small groups show its shape well. Bees, butterflies, and other insects visit the flowers. Several butterflies also use it as a larval host. Pod-bearing stems add interest to dried flower displays. Indigenous people used ripe pods as rattles and made blue dye. Trimming after bloom helps shape the clump but removes future pods. Cut back the stems once the leaves have blackened.

Serious pest and disease problems are uncommon. Deer and rabbits tend to cause little damage. Plants may struggle near black walnut trees because of juglone. No edible uses are known. All parts can cause poisoning when eaten in quantity. Symptoms include nausea, vomiting, and diarrhea. Historical medicinal uses do not establish that home use is safe.