This worldwide collection features plants of documented wild
origin from nearly every continent, with an emphasis on plants
from mediterranean climates (California, Mediterranean Basin,
Australia, South Africa, and Chile). The arrangement of the
outdoor collections is primarily geographic by continent of
origin or by region including, , , , , , , , and . The Garden
holds one of the largest and most diverse collections in the
United States: 19,300 accessions (each accession represents one
or more plants in the Garden). The five best-represented
families are: Cactus family (2,029 accessions; 1,198 taxa),
Sunflower family (1,002 accessions; 771 taxa), family (1,030
accessions; 711 taxa), Lily family (1,097 accessions; 675 taxa),
and Heath family (979 accessions; 614 taxa). The remainder are
distributed among other families in the collection, including
approximately 690 accessions of ferns and fern allies. Each
genus is assigned to one plant family. These assignments are in
a state of change due to research findi