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June 2017 – June 2019

For the third year in a row, volunteers with The Nature Conservancy and the Rogue Native Plant Partnership gathered on the slopes of Upper Table Rock to collect wildflower seed for future restoration projects and hand pull the highly invasive yellow starthistle.

Yellow starthistle (Centaurea solstitialis) is an exotic annual herbaceous plant in the knapweed genus. The seeds from this plant can germinate whenever there is enough moisture in the soil. It starts as a small bluish green rosette and grows slowly through the winter months. Once the heat of the summer comes this plant bolts to produce yellow flowers subtended by thorny spikes.

Although yellow starthistle is an annual species that dies every year, it is able to produce a long taproot that depletes the soil of moisture making it nearly impossible for native species to grow nearby. This species is particularly difficult to manage because it can continue to produce flowers and seeds even after continual mowing or grazing by producing flowers very low to the ground. At Upper Table Rocks, years of volunteer-based hand-pulling has resulted in the almost complete eradication of this plant from the wildflower meadows at the site!

Ecological restoration involves many steps. The first step is often to change the disturbance patterns at the site (in this case stop the yellow starthistle invasion) followed by seeding the site with native wildflower and grass seeds. These precious seeds are hard to come by and expensive in Southern Oregon. To help tackle these challenges, volunteers with The Rogue Native Plant Partnership help to collect wildflower and grass seeds from native plants nearby. Once enough seed has been collected, it will either be used directly on the site or grown out at a nearby farm (increased) if more seed is needed than can reasonably be collected from wild plants.

AUTHOR:

Kathryn Prive
Rogue Native Plant Partnership

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