At first glance, the leaves of stinging nettle appear as inviting as mint, but casual contact transmits a burning sensation that can linger for days. The hairs are packed with a potent brew of histamine, acetylcholine and serotonin that causes an allergic reaction in mammals. To ease the "bite," rub leaves of coyotebrush, which grows on dry hillsides near the nettle, on affected skin. But stinging nettle has other properties that challenge our desire to label it a nuisance. The plant's juices are reportedly beneficial: as an excellent hair tonic, to reinvigorate the liver and kidneys, to stimulate milk in nursing mothers and to treat prostatic hyperplasia.
Key characteristics: A stout, handsome plant 3 to 10 feet tall. Has opposite leaves with serrated edges, square stems (in cross section) and delicate sprays of loosely hanging flowers.
When a plant lives in the desert but has tender, tasty leaves preferred by every grazing animal in the area, it has to protect itself. Hence the elegant, albeit annoying, solution devised by the aptly named catsclaw. Armed with an array of spines curled like the claws of a cat, this plant readily hooks and tears the sturdiest clothes. Growing 10 to 30 feet tall, catsclaw grows along desert washes where its waxy seeds tumble and scar in abrasive flash floods before they germinate. Overgrazing or absence of wildfire leads to dense thickets. Catsclaw, which blooms in April, provides shade and cover for birds and wildlife.
Key characteristics: Bare-limbed all winter but covered with tiny, gray-green pinnate leaves from spring through fall; dense spikes of flowers form flat, pea-like pods that constrict to reveal the outline of each seed. Thorns are scattered along branches and interspersed with leaves.
Looking deceptively soft at a distance, the teddy bear cholla of Southern California deserts lures unsuspecting hikers, then snags them with horrific spines, which is how cholla reproduces itself. These chunks, when shaken loose, send out roots and grow into clones of the original plant.
Cholla spines are so dense that little of the plant's surface can be seen. They function as shields against the sun's intense rays, and are so effective that the cholla can tolerate some of the highest temperatures of any vascular plant.
Key characteristics: A 3- to 5-foot-tall, many-branched cactus that turns black or brown on its lower stem, while its upper branches shimmer golden or silvery from the reflection of its many spines.