Helianthus (/ˌhiːliˈænθəs/)[3] is a genus comprising around 70 species of annual and perennial flowering plants in the daisy family Asteraceae commonly known as sunflowers.

[7] The species H. annuus typically grows during the summer and into early fall, with the peak growth season being mid-summer.

They grow to 1.8 metres (6 feet) and are primarily found in woodlands, adjacent to creeks and moist, prairie-like areas.

Several ornamental cultivars of H. annuus have red-colored ray florets; all of them stem from a single original mutant.

The rough and hairy stem is branched in the upper part in wild plants, but is usually unbranched in domesticated cultivars.

[12] This genus is distinguished technically by the fact that the ray florets (when present) are sterile, and by the presence on the disk flowers of a pappus that is of two awn-like scales that are caducous (that is, easily detached and falling at maturity).

Another technical feature that distinguishes the genus more reliably, but requires a microscope to see, is the presence of a prominent, multicellular appendage at the apex of the style.

This movement is referred to as heliotropism, which continues for a short time when flower buds form and young Helianthus heads track the Sun.

[17] By the time they are mature and reach anthesis, Helianthus generally stop moving and remain facing east, which lets them be warmed by the rising sun.

[12] Historically, this has led to controversy on whether or not Helianthus is heliotropic, as many scientists have failed to observe movement when studying plants that have already bloomed.

[12][19] Heliotropism persists on cloudy days when the sun is not shining brightly, meaning that the movement is endogenous as a trained and continuous process.

Future studies are required to identify the exact physiological basis and cellular mechanism for this behavior.

are a nectar producing flowering plant that attract pollinators and parasitoids which reduce the pest populations in nearby crop vegetation.

Sunflowers attract different beneficial pollinators (e.g., honey bees) and other known insect prey to feed on and control the population of parasitic pests that could be harmful to the crops.

[23] In addition to pollinators of Helianthus spp., there are other factors such as abiotic stress, florivory, and disease which also contribute to the evolution of floral traits.

These selective pressures, which stem from several biotic and abiotic factors are associated with habitat environmental conditions which all play a role in the overall morphology of the sunflowers' floral traits.