So what is the commonest shrub in California? Poison oak, Coyote bush, lupine? Excellent guesses but all wrong. Actually it is the creosote bush, which covers over 21 million acres, both in the Mojave and in far southern California Deserts. This incredibly successful plant also dominates the large Sonoran desert of Arizona, New Mexico and much of northern Mexico.
The closest living ancestor to this plant is found way south in Argentina. I have seen Magellanic penguins along the Patagonian coast nesting under creosote bushes. That was one incongruous sight for me. Botanists hypothesize that the American golden plover - a long distance migrant that winters in South America - brought seeds of creosote north millions of years ago. Creosote was already adapted for the desert of that new region.
At the end of the last Ice Age as the climate became drier and drier, creosote bushes moved northward and now thoroughly occupy our deserts. Creosotes are the most drought tolerant of any plant. They survive on less than two inches of yearly rainfall and even through years of no rain. They have both a deep taproot and extensive surface roots. In competition for unpredictable rain, creosote bushes exhibit chemical warfare. Their roots secrete toxic compounds that prevent other plants from growing and competing with them for water.
Though creosotes flower prolifically, they mostly reproduce by cloning themselves. In western San Bernardino County, scientists found a circle of creosote bushes 45 feet in diameter. The shrubs are all clones from an ancestral plant, which is thought to have begun growing 11,700 years old, making this group of creosote bushes the oldest living thing on the planet, essentially as old as the desert.
At a Nevada test site there were 20 creosote bushes obliterated by an atomic blast at ground zero. Nineteen of them came back to life. I want to be on their team.