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U.S. Forest Service

Plant of the Week

Map of the United States showing states. States are colored green where the species may be found. Range map of Helianthus hirsutus. States are colored green where the species may be found.

Helianthus hirsutus. Hairy sunflower plant. Photo 2011 David D. Taylor.

Helianthus hirsutus. Close up of flower head. Photo 2011 David D. Taylor .

Helianthus hirsutus. Leaves and stem. Photo 2011 David D. Taylor.

Hairy Sunflower (Helianthus hirsutus Lam.)

By David Taylor

Hairy Sunflower is a member of the Asteraceae, the Sunflower family. In older manuals and guides, this family is called the Compositae because the 'flowers' are a composite of many flowers, often of different types. The many species of plants in this family are grouped based on the arrangement and type of flowers. All members of the family produce one or more heads (capitulum, the term used in technical keys) of flowers. This and other sunflowers have two different types of flowers, ray flowers and disk flowers and in turn, these can have male and female parts, or either one or the other. The ray flowers look like petals, but each is actually an individual flower. The disk flowers are at the center of the head, inside the ring of ray flowers. The disk flowers are usually small. With a hand lens one can see the distinct tips of 5 petals in each flower. The disk flowers closest to the ray flowers open first.

This sunflower is 0.5 - 1.5 m (1.6 - 5 ft) tall. The stem is rigid and covered in coarse spreading hairs. Leaves are opposite (rarely alternate near the top), wider at the base than the top, and are 5 - 15 cm (2 - 6 in) long by 1 - 8 cm (0.4 - 3.1 in) wide. The leaves are covered in dense rough hairs, top and bottom resulting in the common name. Heads are generally borne individually or in clusters of 2 or 3, and are found at the top of the plant. Each head generally has 10 -15 ray flowers that are 1.5 - 3.5 cm (0.6 - 1.4 in) long, and numerous disk flowers. Both the ray and disk flowers are yellow. The center of the containing the disk flowers is 2 cm (0.8 in) wide. The entire head is 3.5 - 5.5 cm (1.4 - 2.2 in) wide.

Hairy sunflower is an open land and open forest species, generally on drier soils. It is a species of prairies and other grasslands, old fields, roadsides, savannas and woodlands, and upland forest without a dense shrub layer. It also occurs in forest openings. It is found from Minnesota, Iowa, and Nebraska south to Texas and east to New York and Connecticut south to Florida, with the exception of New Jersey. It is also known from Ontario. It is most common in Missouri, Arkansas, Louisiana, Illinois, Kentucky, and Tennessee. It is also known from Coahuila and Nuevo León, Mexico.

This species flowers in July to October depending on the part of the country in which it is found. It is a strong competitor in the garden and can soon become weedy. It does attract numerous finches which eat the seeds directly from the heads.

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