What is Crotalaria?

Crotalaria, commonly known as rattlepods, is a genus of woody shrubs and herbaceous plants that contains more than 600 species belonging to the family Fabaceae. At least 500 species are natives of Africa, and the rest thrive in many countries around the world, mostly in tropical areas. Some people cultivate select Crotalaria species as ornamental plants. Crotalaria plants are often hairy and erect, and their leaves are simple, alternate, and finely haired under the surface. These annual and perennial plants have yellow flowers with a leguminous calyx and lanceolate to obovate leaves.

Other common names of plants that fall under this genus are longbeak rattlebox and chipilin. The name rattlebox comes from the fact that as the heart-shaped seeds mature, these seeds detach, become loose in the pod, and produce a rattling sound when shaken. Derived from the Greek word crotalus, the name of the genus also means castanet.

Considered a soil builder in India, a species called Crotalaria spectabilis was introduced to the United States for green manure. Being a legume, it has the ability to support nitrogen-fixing bacteria. It is very useful in the management of soil fertility as well as weed control. The other Crotalaria species used for various purposes in farm lands include C. ochroleuca, C. paulina, and C. grahamiana.

Throughout the southeastern part of the United States, C. spectabilis has spread fast and is considered an invasive species. Another species, C. longirostrata, is a common leafy vegetable in Central America and Oaxaca, but is treated as a weed in the United States. Several species, such as C. retusa, C. spectabilis, and C. sagittalis, have been associated with livestock poisoning.

The foliage and seeds of Crotalaria plants contain pyrrolizidine alkaloids. These alkaloids, when converted into toxic pyrroles by liver enzymes, may result in lung and liver poisoning in horses. Crotalaria poisoning can be either chronic or acute. Other animals that are susceptible to these toxic alkaloids are domestic fowl, swine, and cattle. On the other hand, goats and sheep are more resistant to this toxic plant.

Most Crotalaria species are used as a food source by some of the larvae of Lepidoptera species, such as Utetheisa ornatrix, Etiella zinckenella, and Endoclita sericeus. The toxic alkaloids produced by some plants under this genus are incorporated by the larvae of Utetheis species and serve as their defense against predators. These harmful compounds are readily absorbed when inside their digestive tract.