Tom's Blog

Wednesday, September 2, 2009

Sawtooth sunflower

I have been spending quite a bit of time lately seeking out various sunflower species at Pleasant Valley Conservancy. Since they are all clonal species, and either actually or potentially invasive, they are of considerable importance. Most of our sunflower clones are of the species Helianthus divaricatus, which goes by the common name of woodland sunflower. However, we have always had a small amount of Helianthus grosseserratus (sawtooth sunflower) in our wetland. This never bothered me because it seemed like it was staying put.

Recently, however, sawtooth sunflower has started to spread. I have now found four relatively small clones in the Valley Prairie. These were definitely not planted there, and since this prairie is now in its seventh growing season, its presence is quite a surprise. The photo above shows what one of these four clones looks like. Admittedly, it is not large, but since it spreads by underground rhizomes, it has the capability of moving into already established prairie. Near to this particular clone is a fine population of Gentiana alba, a State Threatened species. I'm not too interested in losing that.

You can tell that sawtooth sunflower is a potential problem since it has a Coefficient of Conservatism of 2, pretty far down the scale.

However, a quick search of the literature has not uncovered any suggestion that it is able to invade planted prairies, as has happened here. I plan to keep an eye on it for next year. I have installed a permanent marker at each of these clones, and have recorded its GPS coordinates. We'll see!


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