Risks of Desert Plants

Spines

• Many cacti and other succulents possess formidable armor that can inflict serious wounds. Century plants (Agave spp.) often have saw-toothed leaves with sharp points on leaf tips. Yuccas (Yucca spp.) usually have sharp-tipped leaves. Cacti have two types of spines, thick ones that are obviously dangerous to contact and very fine, hair-like spines called glochids that are easily dislodged and dangerous to breathe in or to get in skin or eyes. Century plants and yuccas are hardy to U.S. Department of Agriculture plant hardiness zones 5 through 10, depending on the species. When landscaping with these plants, locate them away from paths and wear protective clothing when pruning or handling them.

Thorns, Hairs and Prickles

• As you hike through desert areas, you'll find that many trees, bushes, perennial and annual plants have sharp branch ends, thorns or other penetrating structures that grab onto clothing or skin. Members of the legume family, such as whitethorn acacia (Acacia constricta) and ironwood (Olneya tesota), have sharp, recurved thorns that resemble cat's claws along their branches. Trees and shrubs with pointed branch ends include palo verde (Cercidium spp.), desert wolfberry (Lycium andersonii) and graythorn (Ziziphus obtusifolia). Whitethorn acacia is hardy in USDA zones 7 through 11, and ironwood to USDA zones 8 and 9. Palo verdes grow in USDA zones 9 and 10, desert wolfberry in USDA zones 9 through 11, and graythorn in USDA zones 8 through 11. Annual plants can also have irritating prickles or hairs, such as thistles (Cirsium spp.), buffalo bur (Solanum rostratum) and fiddleneck (Amsinckia intermedia).

Toxic Substances

• Succulent plants that possess toxic chemicals include century plant, which contains oxalate crystals and irritating substances that can irritate the skin and mucous membranes and can cause digestive problems. Succulent euphorbias (Euphorbia spp.) contain a toxic milky latex that irritates skin and eyes. They are native to Old World subtropical and tropical deserts, primarily Africa and Madagascar, and are hardy in USDA zone 10 and up, depending on the species. Nonsucculent arid land plants containing toxins include the annual sacred datura (Datura wrightii) and oleander (Nerium oleander), all parts of which are poisonous, even the smoke from burning branches. Oleanders are hardy in USDA zones 9a through 11.

Invasiveness

• Some examples of arid land plants that have invasive potential are prickly pear cacti (Opuntia spp.), which were introduced into Australia from the Americas. Rapidly spreading, millions of hectares of Australian land were infested with prickly pear and deemed useless for agriculture as of 1920. Prickly pears grow in USDA zones 3b through 11, depending on the species. Buffalo bur, native from Mexico to the Midwest, is a noxious weed of barnyards, pastures and roadsides. Puncturevine or goathead (Tribulus terrestris) is an annual that is native to the Mediterranean area and has invaded North America. It possesses sharply spined fruits that can puncture bicycle tires.