Most often, the term refers to the Common Sunflower (Helianthus annuus). Common Sunflowers are native to West Sacramento and are also grown locally for commercial seed production. They can be found both in farm fields and in personal gardens. Sunflower seeds are one of Yolo County's highest-grossing agricultural commodities. They are annual herbs that can grow as much as ten feet tall but typically stay only two to three feet wide. Their flower heads can be up to 8 inches in diameter. They like full sun and usually grow in dry, unwatered places.
In addition to Common Sunflowers, two other sunflower species are also native to West Sacramento.
Serpentine Sunflower (Helianthus bolanderi) is an annual or perennial herb native to all or nearly all of West Sacramento. It grows three to five feet tall and about equally wide, with many stems branched from ground level. It prefers full sun and 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 southern two thirds of West Sacramento. It can grow as much as eleven feet tall and nearly four feet wide. It prefers full sun and 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 patches of West Sacramento (mostly along the Sacramento River and the Deep Water Ship Channel) 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.