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Showy rattlebox (Crotalaria spectabilis) is a fast-growing, toxic annual legume originating from Asia, recognized by its bright yellow, pea-like flowers and inflated, rattling seed pods. Often found in the Southeastern U.S. as a weed in disturbed areas, it grows 0.6–1.5 meters tall, blooms in late summer, and contains dangerous alkaloids that cause fatal liver damage in livestock.
Key Facts About Showy Rattlebox:
Appearance: The plant features large, simple, alternate leaves, green-to-purple ribbed stems, and yellow flowers, often resembling a "pea" flower.
The "Rattle": The common name comes from the inflated 5 cm long, Vienna sausage-shaped, seed pods, which rattle loudly when dry due to loose seeds inside.
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Toxicity: It is highly poisonous to all livestock, including horses, cattle, chickens, and quails. The seeds have the highest concentration of toxic pyrrolizidine alkaloids, which cause irreversible liver damage and are dangerous even when dried in hay.
Invasive Status: Introduced as a cover crop for soil nitrogen fixation, it has become a serious agricultural weed, particularly in the Southeast U.S., where it is listed as a noxious weed.
Life Cycle: A summer annual, it germinates in spring, blooms late summer, and sets seed in the fall.
Ecological Role: While toxic to mammals, it is a host plant for the Ornate Bella moth (Utetheisa ornatrix), which feeds on the plant and incorporates the toxins for protection against predators.
Management:
Showy rattlebox can be controlled with herbicides like 2,4-D or glyphosate, with the best control occurring during the seedling stage. Due to its danger to livestock, it should be removed from grazing areas.
