Desert conditions are difficult on living things and those that adapt to it are tempting targets for other desert dwellers looking for food and moisture. This being the case, many desert pants have developed the means to protect themselves. Without desert know-how and care, those running afoul of such plants risk injury, drugging or poisoning.

Barrel Cactus

Cactus plants protect themselves with sharp spines. A great example is the barrel cactus, which is of the genus Ferocactus, the fero- part coming from the Latin word for fierce. Barrel cacti are, indeed, fierce, with the cylinder- or globe-shaped body of the plant bristling with three- to four-inch spines. The spines are sharp enough that Native Americans used them for sewing. The plant, depending on the species, can grow up to about 10 feet tall. It's the largest cactus found in North America.

Datura

Though individuals seeking hallucinogenic experiences have ingested this plant, Datura is poisonous--not just the leaves or the flowers or the fruit or the stem, but all of it. Datura blooms from spring through autumn, with the large trumpet-shaped flowers opening in the evening. The flowers as well as the leaves are about six inches long on a plant that grows about two feet tall. Datura produces fruit that, like so many desert plants, possesses spines. The fruits are about 1½ inches across.

Texas Mountain Laurel

The Texas mountain laurel is also known as the mescal bean plant. As a shrub, it's a member of the legume family, but like datura, all parts of it are toxic to animals and humans. Unfortunately, the plant also has a reputation as a hallucinogen, which entices some to experiment with the potentially fatal plant. The Texas mountain laurel has fragrant purple flowers, and even the scent is reputed to be toxic. Sheep and goats eating mature foliage in quantities that equaled about 1 percent of the animal's weight had attacks of sickness for up to 12 days, according to the Texas Natural Resource Server's Toxic Plant DataBase.

Silverleaf Nightshade

Silverleaf nightshade is often prickly, and both the leaves and fruit are poisonous, containing the toxic agent solanine. When ingested, silverleaf nightshade causes diarrhea, nausea and vomiting and abdominal pain. The ripe fruit is the most dangerous. In certain exacting amounts, the berries are used as part of the process of making asadero, a Mexican goat milk cheese.

Tree Tobacco

Tree tobacco is native to South America, but has adapted to life in the southwest United States. Flowers might be white, green, red or yellow, and they open at night. Though its scientific name--Nicotiana glauna--might lead you to believe the leaves of tree tobacco are smokeable, this isn't the case. Poisoning leads to diarrhea, dizziness, altered vision and hearing. Tree tobacco can also cause auditory hallucinations.