Tom's Blog

Friday, July 24, 2015

Helianthus occidentalis: a well-behaved sunflower

Readers of this blog may be aware of the problems we have with invasive sunflowers, members of the genus Helianthus. Our biggest problems are the various woodland sunflower species, especially H. divaricatus, and H. decapetalus. In addition, sawtooth sunflower (H. grosseserratus) overflows some wetland areas, and Jersusalem artichoke (H. tubersosus) is lurking here and there. Even showy sunflower (H. pauciflorus) is a potential invader.

That is why I was delighted to discover a nice small patch of western sunflower, H. occidentalis, in the Pocket Prairie.

According to the Illinois wildflower website, this species "is usually found in higher quality habitats..." and the Prairie Moon website says: "Western Sunflower is well-behaved, compared to some of the more aggressive Helianthus species."

Of course, our population came from seed, planted I don't know how many years ago. Because of its delicate nature, it may be hard to find in a lush planted prairie. I was concentrating on populations of white and purple prairie clover when I found nearby the patch shown on the photo.

Western sunflower in the Pocket Prairie
As the photo shows, the flower stalks of this species are virtually bare, all of the leaves being in basal rosettes. It has a Coefficient of Conservatism of 6. 


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