This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Native. Annual. Propagates by seeds.
Time of bloom: June to July.
Seed-time: August to October.
Range: Massachusetts to Florida, along the coast; bottom lands of the Missouri River in South Dakota, Iowa, Nebraska, Kansas, and northern Texas. Habitat: Rich, moist soil; pastures and meadows.
This plant is the cause of a sickness, called Crotalism by veterinarians and Missouri Bottom Disease by the farmers, which is often fatal to horses and sometimes also to cattle, though deaths are less frequent with the latter than with horses. The poisonous principle is in both leaves and seeds, and is not dissipated by drying but seems to be even more potent in plants that have been harvested with hay than in those that are green in the field. Its action is slow, often several weeks intervening before death. If recovery comes it is not complete, the animal being never so well again as before the attack of Crotalism. The weed is a relative of the dreaded Loco-weed of the plains, but does not cause the animals to "go plumb crazy," as does that plant. (Fig. 159.)
The plant is small, seldom more than a foot in height, with a much-branched and hairy stem growing from a small, straight root. Leaves alternate, nearly sessile, lance-shaped, one or two inches long, pointed at both ends, entire or slightly wavy, with edges softly hairy; they have curious stipules, shaped like an arrow-head, point down, with the ears sticking up on each side of the leaf and the point decurrent on the stem for a part of its length. Flowers yellow and very small, shaped like pea-blossoms, that is, with a corolla of five irregular petals, the upper one larger than the others, and enclosing them in the bud; this broad upright petal is called the standard and is usually turned backward; two lateral petals or wings, obliquely spread and outside of the two lower ones which cohere at their edges, forming the keel, which usually encloses the stamens and pistil. In this species the stamens are ten, one separate and nine of them united into a tube, cleft on its upper side, the anthers of two lengths and sizes, alternating with each other; calyx two-lipped, the two upper lobes broadest, all five long-pointed and softly hairy. The flowers grow in clusters of two or three on slender, axillary peduncles. Pods black, very hard and brittle, about an inch long but swollen much larger than the small, black seeds within, which break from their hold when ripe and rattle about inside the stiff, thin walls. In winter these light pods are blown long distances over the snow, and they can float like a boat on water.
Fig. 159. - Rattlebox (Cro-talaria sagittalis). X 1/3.
Let the infested meadows be cleansed by fire, burning them over in August or at the time of maturing seeds, thus destroying all this year's plants and their progeny while not seriously harming the roots of the perennial grasses. If next year some seeds that have lain dormant in the soil spring up, see that the plants are either cut or pulled before seed development. Or, if too numerous for that, repeat the flaming purification. On lands that are not in danger of washing and can safely be put under the plow, a cultivated crop requiring careful hoe-culture should be grown before reseeding heavily with better forage. No annual plant so dangerous to the health of grazing animals should be allowed to survive.