Sunflowers are members of the Helianthus genus of the Aster family (Asteraceae). Most often, the term refers to the Common Sunflower (Helianthus annuus). Common Sunflowers are native to Davis and are also grown locally for commercial seed production. They can be found in both personal gardens and farmer's fields just outside of town. The seeds harvested from the farm fields will be planted throughout the world for confection, oil, or ornamental markets. Sunflower seeds are one of Yolo County's highest-grossing agricultural commodities, with over $11,000,000 worth of seeds harvested in 2010. Two varieties are planted for cross-pollination, and European honeybees are used to supplement the native bees that pollinate the flowers.
In addition to Common Sunflowers, two other sunflower species are also native to Davis.
Serpentine Sunflower (Helianthus bolanderi) is an annual or perennial herb native to all of Davis. It prefers full sun and grows three to five feet tall, with many stems branched from ground level. It can grow equally well in wetlands or in drylands, adapting its size to suit the amount of water available.
California Sunflower (Helianthus californicus) is a perennial herb native to the far southeastern edges of Davis. It prefers full sun and can grow as much as eleven feet tall. It grows exclusively in wetlands.
Some other yellow flowers in the Aster family are commonly called "sunflowers" but are not true sunflowers. The most notable of these is probably the Woolly Sunflower (Eriophyllum lanatum), which is native to Davis and can grow about three feet tall and wide in dry soil and full sun or partial shade. A cultivar called 'Siskiyou' is commonly sold that stays shorter. Although Woolly Sunflowers are in the same plant family as true sunflowers, they are not otherwise particularly closely related, being not only in different genera but also in different tribes of the Asteroideae subfamily.