Crotalaria spectabilis aka Rattlebox

Crotalaria spectabilis belongs to the bean family, Fabaceae. Its names include showy rattlebox and cat's bell. It is native from the Indian subcontinent to Taiwan. It has spread through the tropics and southeastern United States. There, it grows in fields, pastures, roadsides, and waste ground. It also occurs in grasslands and along forest edges. This fast-growing plant grows as an annual, though some plants persist. Older stems can turn woody.

Plants reach about 2–5 feet [0.6–1.5 metres] tall. Their upright stems branch above the middle. The stems have ribs and can look green or purple. A waxy coat develops as they age. The green leaves are simple and alternate along the stems. Each has a smooth edge and hairs beneath. Leaves widen toward the tip, then narrow toward the base. They grow about 0.17–0.5 feet [0.05–0.15 metres] long.

Bright yellow flowers form long racemes at the stem tips. Each raceme holds about 20–30 blooms. Some petals show dark red-purple veins near their base. In the southeastern United States, flowering runs from August through November. Bees and other insects visit the flowers. Swollen seed pods follow, turning black as they mature. Each pod holds about 20 seeds. Loose seeds rattle inside dry pods when the wind blows. The pods remain after leaves and flowers die.

Give this plant full sun and soil that drains well. It tolerates some shade, poor soil, and varied soil types. It prefers mildly acid soil but accepts a wider pH range. Established plants can cope with drought. North Carolina State lists USDA zones 9–11. Young growth can suffer severe damage at 30°F [−1°C]. Its long bloom season gives it value as an ornamental. Growers also use it to improve and hold soil. Its stems provide a strong fibre. Reported medicinal uses include treatment for scabies and impetigo.

Its spread and toxicity limit its value in gardens. It competes with pasture plants and seeds itself freely. Birds and other wildlife spread its seeds. Farm tools, crop seed, hay, and forage can also carry them. North Carolina lists it as invasive. All parts are toxic, with the highest concentrations in seeds. It poisons dogs and livestock, even after cutting and drying. Its alkaloids can also harm people, including the liver. Reports describe cooked or pickled flowers as food. Those records do not establish that eating this plant is safe.