In nature, the distribution of plants rarely coincides with political
boundaries, but rather is determined by the interaction of climate,
geology and geography. A regional association of plants that share these
growing conditions is called a
FLORISTIC PROVINCE.
In North America, there are thirteen floristic provinces. Four occur
in California: Californian, Vancouverian, Sonoran and Great Basin.
CALIFORNIAN
is defined by its Mediterranean climate. It is the smallest floristic
province in North America, but has the greatest diversity of plants
north of Mexico. It includes such characteristic vegetation as chaparral,
coastal sage scrub, oak woodland and grassland. These plants exhibit
classic adaptations to California's hot dry summers and cool wet winters.
VANCOUVERIAN
encompasses the state's major forests and includes the mixed evergreen
and coniferous forests of pines, mandrones and coast and sierran
redwoods. In California, this province is transitional between
Mediterranean-climate vegetation and the temperate coniferous
rainforests of the Pacific Northwest.
SONORAN
is characterized by the giant cacti and desert scrub of the American
Southwest and Mexico. At the edge of this province, California's
desert vegetation is defined by joshua tree woodland, fan palm oasis
and creosote bush scrub.
GREAT BASIN
is dominated by the vastness of sagebrush scrub vegetation - the
"sagebrush ocean." The majority of this high-elevation semidesert
lies to the east of California in the rain shadow of the Cascade and
Sierra Nevada mountain ranges.
Rancho Santa Ana Botanic Garden's living collection is gathered from
the entire Californian Floristic Province and the California portions
of the Vancouverian, Sonoran, and Great Basin provinces.
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