Dutchman's Breeches  

Thamnosma texana



Dutchman's breeches is a perennial weed that is a member of the citrus family. The plant is usually about 6 inches tall with simple, alternate leaves. The flowers vary from canary yellow to purple with a slight yellow center and occur from about May to October. Dutchman's breeches is most easily identified by its strong, aromatic smell when bruised. Its fruit is unique, shaped like inflated Dutchman's breeches with the legs projecting upward. Used medicinally by American Indians of the Southwest, the plant has been eaten as a tonic and used to treat gonorrhea.


This plant is distributed widely in gravelly calcareous soils in Texas, New Mexico, Arizona and California. In Texas, it is common in the Rio Grande Plains, southern and western parts of the Edwards Plateau, the Trans-Pecos and southern parts of the Plains.

Toxic Agent

The toxic properties of Dutchman's breeches can be attributed to the presence of psoralens (strong photosensitizing agents) in the plant. Sheep consuming about 1 percent of their body weight of this plant have shown signs of primary photosensitization within 24 to 48 hours. Cattle and goats also have shown primary photosensitization when grazing areas with large amounts of Dutchman's breeches. Humans who get plant sap on their skin suffer severe sunburn in contacted areas.

Signs of Livestock Ingestion

Signs of primary photosensitization include: Increased body temperature; Photophobia (animals avoid sunlight); Edema of the muzzle, ears and vulva; Inflamation and edema of the eye.

Management Strategies

Sheep and goats like the taste of Dutchman's breeches and can be expected to graze this weed, perhaps heavily in areas where more palatable forage plants are less available. Most poisoning cases have occurred when sheep or goats were placed in pastures that for several years had been grazed only by cattle. Where sheep and goats have historically grazed continuously, the plant has been almost eliminated and no longer threatens them. However, the plant may still be abundant over the fence along a highway. Pasture rotation and/or supplemental feeding may help prevent consumption of Dutchman's breeches. When the first cases of photosensitization occur, move the animals to new pasture if possible. Place sick animals in the shade with feed and water. Painting or spraying the affected skin areas with methylene blue solution or some other nontoxic dye is beneficial. Avoid applying grease, oils or tannic acid.