The plant genus Larrea of the Zygophyllaceae family is one of the few genera that contains only one species — Larrea tridentata, or creosote bush. The creosote bush, sometimes called greasewood, is an evergreen perennial shrub of the southwestern US and northern Mexican deserts. The name creosote bush comes from the distinctive odor that the plant emits. Most botanists and scientists believe it is one of the oldest plants in the world.
The most famous Larrea plant may be King Clone, which lives in the Lucerne Valley region near Barstow, California. Scientists carbon dated some of the plant's dead wood and believe it is almost 12,000 years old. Generally, when a creosote bush is 30 to 90 years old, new growth develops around the old wood, and eventually the center dies out. King Clone's circle is approximately 45 feet (13.7 m) in diameter. These plants are very slow growers, and a 1-foot (about 30-cm) high bush may be approximately ten years old.
Larrea plants possess a substance that slows or inhibits viral and bacterial cells from replicating themselves. Botanists theorize that this chemical action is one reason why Larrea plants live so long. Another survival tactic of the creosote bush is the fact that resins that it emits inhibit the growth of nearby plants, creating a barren zone around the plant.
Creosote bushes have the ability to survive during long periods of drought. By eliminating neighboring plants that would compete for the water, it ensures that it receives any rainfall that may occur. The plant's extremely efficient root system, which deprives seeds and other plants of water, consists of a long taproot and web of shallow roots.
The Larrea plant has evergreen, alternate leaves that have a waxy or varnish-like coating that helps the plant conserve water. The yellow, velvety flowers often have five oblong petals that some people describe as spoonlike. Some petals may be long, narrow, and curved like a sickle. In the flower center, it has ten stamens surrounding one pistil. The plant bears capsule-like, hairy fruits that typically are on the plant simultaneously with the blooms.
A mature Larrea plant generally is about 4 to 8 feet (about 1.2 to 2.5 m) tall and 4 to 6 feet (about 1.2 to 1.8 m) wide. Typically, growers propagate the plants by sowing the seeds or by taking softwood cuttings. Gardeners often use the plants as hedges for wind lockage or privacy. Native peoples used various parts of the plants to treat a multitude of ailments, including tuberculosis, chicken pox, and even snakebite. Some used it to treat a menstrual disorder called dysmenorrhea. In modern times, the United States Food and Drug Administration and Canada's Health Canada warn that users risk severe liver and kidney damage. Despite these warnings, some businesses sell supplements made from L. tridentata for weight loss, detoxification, and even cancer and AIDS.