Plant Walk - Stop Number 37



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Creosote
(Larrea tridentata)
NORTH OF STAIRCASE ON WEST SIDE OF OLD MAIN

37	Native to the Southwestern deserts and northern Mexico , its yellow flowers appear mainly in the spring, followed by small, fuzzy seed balls. The leaves secrete a gummy resin that makes them look lacquered and contributes to the pungent fragrances after rains.

In Depth	Larrea tridentata, Creosote
	Location: NORTH OF STAIRCASE ON WEST SIDE OF OLD MAIN
	Family: Zygophyllaceae, the caltrop family
	Distribution: throughout the warm North American deserts, from Nevada to central México, up to 1600 m (5200 ft) in elevation
	Habitat: semi-desert grassland, chaparral, thornscrub, desertscrub, conifer woodland
	Habit: slender-branched shrub up to 3.5m
	Flowering: any time following rain, even in winter
	Natural History Notes: Creosote is one of the most prominent plants in our deserts, covering thousands of square miles, often in pure stands, often with plants of equal size. Most closely related to Larrea divaricata of South America, it has been hypothesized that our creosote came up from South America before the more than 11,000 years ago, moved into the Chihuahuan desert, from there to the Sonoran Desert, then to the Mohave Desert. Creosote is very well adapted to heat and drought, surviving in places where apparently little else can. It has an extensive root system, much of it very shallow, and chemicals exuded by the roots are known to inhibit some other shrubs' roots, including creosote, which may in part explain the stands of evenly spaced plants. A slow grower, it takes at least 13 years for reproductive maturity. New stems arise from the base of the plant at the outside edge, and when old stems eventually die (after 40-90 years), a space is created in the middle. In this way, clones of single plants form rings, the largest and oldest of which are estimated to be 11,700 years old. Over 40 insects are known to be wholly or partly dependent on creosote.