Scientific Name: Drymaria pachyphylla
Distribution: Texas, New Mexico, and Arizona, and south into Mexico
Type of Poison: Unknown
Signs of Poisoning (in this order):
Growth Characteristics: Inkweed, also known as drymary, is a glabrous, short-lived annual which grows in a circular pattern close to the ground, reaching 8 to 10 inches in diameter.
Flowers and Seeds: Small flowers are produced in clusters in the axils of the leaves. Individual flowers typically have five sepals and petals, the petals deeply lobed or divided. There is usually one style and five stamens. The fruit is a small capsule, splitting when ripe by three valves. A purplish juice emanates from the green capsules and unripe seeds when squeezed.
Leaves: Leaves are blunt tipped and usually about as wide as they are long.
Inkweed prefers areas with sparse vegetation. It is often found on heavy, alkaline clay soils and in low areas subject to occasional flooding. The plant is usually not abundant except on disturbed sites.
Cattle, sheep, and goats are known to be poisoned by inkweed. Both dry and green plants are toxic, and all parts of the plant are toxic. Poisoning usually occurs on overgrazed ranges, and plants are most commonly grazed in the early part of the day while they are somewhat swollen. Symptoms appear 18 to 24 hours after ingestion of toxic amounts. The period between the onset of symptoms and death is quite short, often less than two hours. As a result, symptoms are not easily observed under range conditions. Feeding experiments have shown that 0.6% of the body weight of the plant will kill a sheep, 0.4% a cow, and 0.9% a goat.
Inkweed is very unpalatable to all classes of livestock. Thus, poisoning generally occurs only when other forage is limiting. To reduce these losses, range management practices that promote improved range conditions and increased diversity of forage are beneficial. Special caution should be observed during drought years.
Dayton, William A. Notes on Western Range Forbs: Equisetaceae through Fumariaceae. Forest Service, U.S. Department of Agriculture, Washington, D.C. 1960.
Department of Ecosystem Science and Management, Texas A&M. Inkweed, Thickleaf Drymary. Texas Toxic Plants Database. 2009. Texas A&M Extension Service. 23 July 2009. http://essmextension.tamu.edu/plants/plant/inkweed-thickleaf-drymary/
L.F. James, R.F. Keeler, A.E. Johnson, M.C. Williams, E.H. Cronin, and J.D. Olsen. Plants Poisonous to Livestock in the Western States. U.S. Department of Agriculture, Agriculture Information Bulletin 415, 90 pp. 1980.