hanging out with friends...or enemies

The sunflower serves as a low food source, 5-10% of diet for large and small mammals as well as terrestrial birds. 

The sunflower has showy ray petals which attract birds and butterflies, although the sunflower can be harmed by birds because the seeds are exposed and they are able to perch on the large head of the sunflower.  On the other hand, the sunflower is frequently visited by butterflies due to its large surface area and high probability of finding nectar because of the numerous disc flowers.

Helianthus annuus has a mutualistic relationship with mycorrhizae, this relationship between a plant and fungus can be seen in 95% of plants.  The sunflower benefits by an increase in biomass as well as increased access to phosphorous, water, nitrogen and other immobile nutrients.  On the other hand, the mycorrhizae receives sugars produced by the plant.

The sunflowers share a predatory relationship with weeds because they cause the crop to be reduced by competing for moisture, nutrients and light.  On the other hand they share a mutualistic relationship with bees because the flower gains transport of pollen while the bee gains an abundance of nectar.

Helianthus annuus includes a number of insect pests, including: Midge, Head Moth, Beetle, Maggot, Head Clipper Weevil, Stem Weevil Complex.  Along with pests comes disease, which includes: Downy Mildew, Rust, Sclerotinia Stalk and Head Rot, Vericillium Wilt.  Although there has been some resistance to disease shown when Helianthus annuus is hybridized with Helianthus tuberosus (Jerusalem artichoke).

Within the food web, Helianthus annuus falls as a primary producer.  It is an autotroph which produces its own food via photosynthesis.  It is the first trophic level within the web, because it supports the other levels.