Showy Rattlebox

Crotalaria spectabilis

Taxon biology 6

Showy rattlebox, Crotalaria spectabilis, is a legume (Family Fabaceae) native to the Indo-Malaysian area but has been widely planted around the world’s tropics where it grows in open and disturbed areas.  It is one of about 600 described species in the genus.  A fast grower, C. spectabilis lives 2-3 years as a shrub in tropical areas, as a semi-woody annual in temperate climates.  It was introduced to the US from the Indo-Malaysian area as a fodder plant, for green manure, and as to build soil fertility, as it has root nodules that support nitrogen fixing bacteria.  However, it is also poisonous to many agricultural animals including cattle, horses, swine, and poultry, so these practices are now mostly abandoned.  Since its introduction, C. spectabilis has spread rapidly throughout the Southeastern United States, where it is now considered an invasive species and a noxious weed (Francis, 2002; USDA, ARS; Wikipedia 2014; LSU AgCenter 2014). 

The primary toxic compound synthesized by Crotalaria spectabilis is monocrotaline (MCT), a pyrrolizidine alkaloid.  When amounts up to 1.5-3% of bodyweight are ingested (all at once or over several months), C. spectabilis may cause acute poisoning, causing liver failure and death within a few days of ingesting the plant.  Crotalaria poisoning can also manifest in animals as a more common uncurable chronic fibrosis of the liver, occurring weeks or months after eating C. spectabilis, and leading to emaciation and death (LSU AgCenter 2014).  When administered to rats, monocrotaline causes remodeling of the pulmonary vascular system, which causes lung damage and hypertension.  MCT is used in research labs as pathway to create an animal model of pulmonary hypertension for examining the function of ventricle muscle hypertrophied (enlarged) by chronic hypertension and to develop medical treatments and drugs for this condition (see, for example Werchan et al. 1989, Kosanovic et al. 2011; reviewed in Schultze and Roth 1998).

Larvae of the ornate moth (Utetheisa ornatrix), also known as the rattlebox moth, feed on the plant and re-purpose the poisonous compound as a defense, excreting it when they are threatened by potential predation (Wikipedia 2014).  Bees polinate the bright yellow flowers (Francis 2002). 

In India, extracts of the whole C. spectabilis plant are used as traditional medicines to treat impetigo, scabies, intestinal worms, and as an antiseptic for wounds (Francis 2002). 

The name "rattlebox" refers to the rattling of the seeds in the pods once they dry (Francis 2002).

Sources and Credits

  1. (c) John D. Bird, MS State University, USA,, some rights reserved (CC BY),
  2. Steve Hurst, no known copyright restrictions (public domain),
  3. (c) Cooper, G.A., some rights reserved (CC BY-NC-SA),
  4. (c) Cooper, G.A., some rights reserved (CC BY-NC-SA),
  5. (c) Ingrid P. Lin, some rights reserved (CC BY-NC-SA),
  6. (c) Dana Campbell, some rights reserved (CC BY-SA),

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