Creosotebushes ply another strategy. These regularly spaced shrubs look as though human beings had planted them because they produce a toxin in the leaves that, when shed, discourages other plants from intruding on their growing space. The small creosotebush leaves are coated with a resin so that they lose little moisture to the air. These combined strategies make creosotebush the most prevalent shrub in the park and enable it to prosper in all North American deserts. Creosotebushes that grow along a road, tap pavement runoff and may grow twice as tall as those one row back from the road.
Cactuses exemplify water conservation.
Instead of water-losing leaves, cactuses have spines. The thick and fleshy stem presents reduced surface area and bares a waxy coating that inhibits evapotranspiration. The shallow root system spreads in a wide pattern to intercept rainwater as soon as it enters the ground. Cactuses store water, serving as their own reservoirs and surviving long droughts. The ocotillo, not a cactus, is in a family by itself.