INDIAN HEMP
Description
Leaves of the Indian hemp grow on opposite sides along stems that contain a milky sap. The smooth-edged leaves are hairy on the lower surface. Flowers are greenish-white. Two long pods, which develope from each flower, contain numerous seeds with tufts of silky white hairs at the end. The plant grows 2 to 5 feet tall. Leaves turn yellow in the fall. The herb is a perennial in the dogbane family.
Indian hemp a poisonous herb found throughout the United States, causes livestock losses in western range States. The herb gets its name from the fact that Indians used fiber from the bark for making rope. It also is called dogbane, hemp dogbane, Indian physic, American hemp, and rheumatism weed.
Normally, animals avoid Indian hemp because of its bitter, sticky, milk-white juice. Sheep are more frequently affected than other animals; they will eat large quantities of Indian hemp leaves and tops if other forb-type plants are not available. Hungry animals may eat the hemp when they are turned onto harvested fields or new range in the fall, or when other forage is scarce. Poisoning also occurs when sheep, cattle, and horses are trailed from summer to winter ranges.
Leaves are poisonous at all times, even when they are dry. The chief toxic substance in Indian hemp is thought to be cymarin, a glycoside. It once was used as a heart stimulant for humans.
Where and When It Grows
Indian hemp grows on plains and foothills at elevations up to 7,000 feet. It commonly is found in gravelly or sandy fields, in meadows, and along creek beds, irrigation ditches, and fence lines in cultivated pastures.
The plant begins its growth in late spring or early summer.
How It Affects Livestock
Death from Indian hemp poisoning may occur 6 to 12 hours after animals eat the plant. A lethal dose for sheep is about 1/2 to 1 ounce per 100 pounds of body weight. A lethal dose for cattle and horses is about 1/2 to 3/4 ounce per 100 pounds of body weight.
Signs of poisoning
1. Increased body temperature and hard, rapid pulse
2. Vomiting
3. Dilation of the pupils
4. Blue coloration of lining of the mouth and nostrils
5. Progressive weakening with marked irregular gait
6. Coma, followed by convulsions
7. Marked, labored breathing just before death.
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