Western sunflower | The Morton Arboretum

Family (English) Aster
Family (botanic) Asteraceae
Tree or plant type Perennial
Native locale Chicago area, Illinois, North America
Size range Large plant (more than 24 inches)
Light exposure Full sun (6 hrs direct light daily)
Hardiness zones Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8
Soil preference Dry soil, Moist, Sandy soil, well-drained soil
Tolerances Alkaline soil, clay soil, Dry sites, Occasional drought
Season of interest late summer, early fall
Flower color and fragrance Yellow
Shape or form Narrow, Upright
Growth rate Moderate
Wildlife Birds, Butterflies, Game birds, Game mammals, Insect pollinators

Size and method of spreading:

Western sunflowers mature to a height of 2 to 4 feet and a spread of one-and-one-half to 2 feet. They spread by self-seeding and sending up clones from underground stem structures (rhizomes).

Native geographic location and habitat: (include C-value if appropriate)

Western sunflowers are native to the Eastern and Central United States. C-value: 10.

Attracts birds or pollinators:

Western sunflowers attract a number of pollinators, including multiple species of bees that specialize in sunflowers. In addition, other species of common bees, butterflies, and flies are visitors of Western sunflowers. They may also attract caterpillars of moths and butterflies. Small mammals and multiple species of birds like to eat Western sunflower seeds, and some larger herbivores may munch on some of the leaves.

Leaf description:

The majority of the leaves of Western sunflowers grow around the base of the plant in a basal rosette. These basal leaves are wide at the base, oval to triangular in shape, and attached by long stalks. The leaves that grow from the central stem occur in widely spaced pairs (opposite arrangement). All Western sunflower leaves have smooth edges (entire margins) or have small, sparse teeth (slightly serrate margins).

Flower description:

Western sunflower flowers are daisylike composites of petallike ray flowers, a center of disk flowers, and leaflike bracts (phyllaries) that are under the base of the flower heads. These composite flower heads occur in groups of one to 12 on individual branching stalks that grow on stems that branch from the long center stem. There are typically between eight and 22 ray flowers per flower head, and they are bright yellow. There are numerous disk flowers that have five lobes and are also yellow.

Fruit description:

Small, single-seeded, dry fruit (achenes) are produced by Western sunflowers. Unlike dandelion achenes, these do not have tufts of hair. They do have two narrow, bristly appendages (awns) at the top. Like other sunflower fruits, the fruit of Western sunflowers are slightly flattened and oblong in shape.

Plant care:

Western sunflowers may require staking for support, and the plants will be most vigorous when divided every three to four years.

List of pests, diseases, and tolerances:

Pests of Western sunflowers include the sunflower head-clipping weevil (Haplorhynchites aeneus), aphids, leafhoppers, leaf beetles, plant bugs, and flower thrips. No serious disease issues are common with Western sunflowers. They are deer resistant. They can tolerate some clay soils, but high contents of clay may require soil amendments.