Catch it early: Two invasive plants to know along the Applegate
Written by:
Luke Wimmer
Two invasive plants in the mustard family are spreading through riparian areas along the Applegate River, and the Applegate Partnership & Watershed Council is asking the community to help us track any known populations.
Dyer's woad (Isatis tinctoria) has a long history with humans. It was the primary source of blue dye for centuries, used to wrap Egyptian mummies, traded across medieval Europe, and worn into battle by Celtic warriors. That same hardiness that made it a reliable crop is what makes it a formidable weed outside its native range.
The plant is a biennial, forming a low rosette of blue-green leaves in its first year and bolting to 2-4 feet in its second, with clusters of small, bright yellow flowers in spring. Seeds develop in distinctive dark, teardrop-shaped pods. It thrives in disturbed soils along streambanks and produces hundreds of seeds per plant. Large infestations have already taken hold along the Rogue and Klamath Rivers, and the Applegate shares many of the same conditions.
Garlic mustard (Alliaria petiolata) has an interesting backstory of its own. European settlers brought it to North America intentionally as a food plant. The leaves are edible and taste like garlic, and the plant was used medicinally for centuries. It has since become one of the most aggressive woodland invasives in North America, spreading rapidly in shaded riparian areas and releasing chemicals into the soil that disrupt the mycorrhizal networks that native trees depend on. It's identifiable by its small white flowers, heart-shaped leaves with toothed edges, and the distinct garlic smell when leaves are crushed.
Garlic mustard has been found along Cheney Creek and the lower few miles of the Applegate for some time, but recent sightings upstream near Ruch suggest it may be moving further into the watershed. Like dyer's woad, it's much easier to eradicate before it gets established.
The Applegate Partnership & Watershed Council has been surveying and hand-pulling dyer's woad in riparian areas since 2016. Thanks to grant funding from the Oregon Department of Agriculture, we're expanding that work along 21 miles of the Applegate River from Williams Creek to the confluence with the Rogue. We're partnering with the Rogue Aquatic Invasives Network (RAIN), the Applegate Paddlers Club, and Ruch Outdoor Community School (ROCS) to cover as much ground as possible. All removal is done by hand, with no herbicides.
If you spot either of these plants along the river, on a trail, or on your property, please let us know. Tracking where these plants are showing up is just as important as removing them, and community sightings help us stay ahead of new infestations.
Contact me at Luke@apwc.info or visit www.applegatepartnership.org.
Luke Wimmer
541-890-9765
Photo 1: Garlic Mustard in flower. Photo: Kyle Strauss.
Photo 2: Isatis tinctoria: Dyers Woad. Photo: Bob Case.
