Toxic Parts:
all, seeds
pyrrolizidine alkaloids
Flower Color:
  • flower color
meadows, haybales, woodlands

Time of Greatest Risk


Geographical Distribution

Showy rattlebox distribution - United States

Related Species

Showy Rattlebox

Crotalaria spectabilis

Kimberly Horse Poison, Sunhemp, Crotalaria Montana, Crotalaria Brevis, Bluebush Pea
7/ 10
Showy rattlebox (Crotalaria spectabilis) is an erect, summer annual that is found worldwide, including throughout the South eastern United States.

Showy Rattlebox Toxic Components

Crotalaria species contain pyrrolizidine alkaloids (PAs) that can cause pyrrolizidine alkaloid toxicity which can result in liver failure. Liver enzymes convert the alkaloids into toxic pyrroles that poison liver and lung cells. In South Africa, they have been shown to cause respiratory disease in horses, referred to as "jaagsiekte" poisoning.

Cases of Showy Rattlebox Poisoning

The most common cause of poisoning cases has been through unknowingly feeding horses contaminated hay and feed. Horses need only to consume 1.5 to 3% of their body weight of the plant parts to start to show symptoms of toxicity. Crotalaria poisoning may be acute or chronic. The chronic form of poisoning is most common and may take several months to years accumulate to where the horse demonstrates symptoms. The acute form appears within a few days after a substantial amount of showy rattlebox is consumed.

What Showy Rattlebox Looks Like

  • Early growth: Turns maroon with age; covered with short hairs. First leaves are alternate, without hairs on the upper portion of the leave, however, is covered with appressed hairs along the lower surface of leaves.
  • Root: Taproot
  • Stem: Green to purplish, erect (up to 6 ½ ft in height), stout; become waxy and angled slightly as they age.
  • Leaves: Alternate, 2-6 inches in length; wide at the apex and tapers to the base. Hairless on the upper surface and covered with appressed hairs on the lower surface; occur on short petioles.
  • Flowers: Large, bright yellow, showy flowers that are on elongated inflorescences and stalked from a central axis.
  • Fruit: 1-2 inch long legume that turn brown to black as they mature. Seeds contained within fruits often cause a “rattlebox” sound when shaken.


  • Appetite Loss
  • Depression
  • Jaundice
  • Colic
  • Nervousness
  • Hyperexcitability
  • Walking In A Circle
  • Pushing Against Objects
  • General Weakness
  • Incoordination
  • Aimlessly Wandering
  • Diarrhea


CHEMICAL: There are a number of chemical control options for showy rattlebox. These include both preemergence and postemergence herbicides in pasture and/or hay, corn, and soybeans. In pasture and/or hay, diuron can used for preemergence control while dicamba, hexazinone, triclopyr, triclopyr mixes, 2,4-D, or 2,4-D mixes can be used for postemergence control.

MECHANICAL: Small patches of showy rattlebox can be mechanically removed by hand. Remove plants prior to fruit ripening to avoid seed dispersal. In pastures, clipping can be an effective method of weed management to minimize exposure of grazing animals to plants that are toxic. Repeat as necessary to minimize likelihood of consumption by livestock and seed production.