Crotalaria spectabilis

Showy crotalaria, is a flowering plant in the Fabaceae (bean) family. It is an annual herbaceous plant that blooms from August to November. Although it is nonnative to the United States, it was introduced to the southeast United States from the tropics. It spans from Virginia south to Florida and west to Texas. It prefers open fields, wastelands, disturbed sites such as pastures and cultivated fields and roadsides with sandy soil and full exposure to the sun.  

It often competes with pasture grasses and other more desirable plants, and its persistent nature often comes out the winner.  In addition to its self seeding, the seeds from this aggressive weedy plant are often spread by birds and other wildlife. 

Its common name rattlebox is derived from the sound made when shaking the dried seed pods.  Remaining on the plant after the leaves and flowers have died, the dry seeds inside the legume become detached.  Winds blowing the pods create a rattling sound.  

Germination begins in the later part of the summer.  In its first stages of growth, its large 6" leaves give it a similar appearance to a head of lettuce or cabbage.  This rapid growing weed can reach heights of up to 5' tall in a short amount of time.  

In the legume family, it will deposit nitrogen into the soil, thus is sometimes used to improve soil conditions.  This introduction into the environment as a cover crop has increased the spread of a weedy plant.  After its introduction, it was soon discovered to be toxic to livestock and dogs.  All parts of the plant are toxic, with the seeds containing the highest concentration.  To prevent loss of animals, plants should be removed from the premises.  If allowed to remain, they will be toxic, even after the plant has been cut and left to die.  Herbicides to manage the growth and spread is the best means of eradication.  

Insects, Diseases, and Other Plant Problems:  It can become weedy in disturbed areas.  It is a serious weed for agricultural lands.  It can spread as a contaminant in farm equipment, crop seeds, forages, and hay.  In the Southeast USA, it is listed as a noxious weed.  

More information on Crotalaria.