Crotalaria sagittalis L.—Rattlebox
FAMILY: Fabaceae (Leguminosae)—the Bean Family
Legume plants are easily recognized by the familiar flowers, typified by garden beans and peas. The flowers are irregular and 5-merous; calyx: if prolonged into a tube, often irregular; corolla: consisting of 5 petals, the upper (standard) exterior and generally larger than the others; the lateral 2 petals (wings) are exterior to the 2 lowest petals (keels), which enclose the stamens and style; stamens: typically 10, their filaments all fused or 9 fused and one free; fruit: a 1-celled pod. dehiscent along both sutures, characteristic of the family.
PHENOLOGY: Rattlebox flowers throughout an extended period from June to September.
DISTRIBUTION: Occurs on dry open soil, waste places, and dry forest clearings.
PLANT CHARACTERISTICS: Crotalaria sagittalis is a small plant growing to less than half a meter tall, with spreading hairs; leaf stipules: decurrent on the stem; leaves: simple, entire, sessile, lanceolate flower on the stem to linear toward the top, 3-8 cm, to l.5 cm wide; inflorescence: 2-4 flowered racemes; flowers: yellow standard, 8 mm; stamens: 10, filaments fused; fruits: oblong, sessile pods, 2-3 cm. very inflated, when dry the seeds rattling in the pods; seeds: flat, kidney-shaped, brown beans, 2.5 mm long.
POISONOUS PARTS: The herbage and seeds are considered toxic. Monocrotaline is present in the entire plant.
SYMPTOMS: Livestock show signs of stupor, labored breathing, weakness, emaciation, paralysis, and death. Postmortem: gross lesions: hemorrhage, petechiae, or large ecchymoses; organ congestion; abomasum, omasum, and gallbladder are edematous; cirrhosis of liver in prolonged cases; histological lesions: pulmonary changes, including emphysema, alternate with atelectasis and hemorrhage.
POISONOUS PRINCIPLES: The toxin is probably the pyrrolizidine alkaloid monocrotaline. The additional alkaloids, fulvine and cristpatine, have been isolated and identified as macrocyclic esters of retorsine, which is also a toxic factor in the composite genus Senecio (see Arctium).
CONFUSED TAXA: Lupines (Lupinus spp.) resemble rattlebox. In lupine the fruit is flattened rather than inflated, and the leaves are palmately compound instead of simple (see Lupinus).
SPECIES OF ANIMALS AFFECTED: Generally horses pastured on land containing Crotalaria sagittalis will show symptoms. One percent of the animal's body weight fed over two days causes death. In one study cattle fed on hay toxic to horses were not affected.
TREATMENT: (11a)(b); (26); possibly treatment with crystalline methionine.
OF INTEREST: Crotalaria sagittalis is more commonly encountered in the southeastern quarter of the Commonwealth. Related species require warmer climates than Pennsylvania provides.