Thousands of butterfly bushes didn’t stand a chance against restoration crews armed with herbicide, shears and chainsaws on the Dungeness River this summer.
The Jamestown S’Klallam Tribe, North Olympic Salmon Coalition (NOSC) and Washington Conservation Corps collaborated to remove the invasive shrub from the lower 11 miles of the river.
After years of piecemeal removal efforts throughout the river valley, the tribe and NOSC teamed up after the coalition received a grant to do the work on a larger scale. The grant allowed for hiring conservation crews, part of the Americorps Program, to cut shrubs to the stump and treat them with an herbicide that is safe for use along streams.
Butterfly bush – also called Buddleja – is an Asian ornamental sold in nurseries, except Oregon and California, where the sale of the shrub has been banned. Contrary to popular belief, the invasive species doesn’t provide habitat for native butterfly larvae. Instead, it crowds out native floodplain species, such as willow and cottonwood.
“Because it spreads rapidly, it can quickly outcompete the native species,” said Hilton Turnbull, Jamestown’s habitat biologist. “A healthy functioning river corridor dominated by native plants is a critical component in the restoration of Dungeness salmon stocks.”
Native trees shade the river, keeping it cool, and help form salmon habitat after they fall into the river, creating pools where salmon can rest, feed and hide from predators, and holding spawning gravel in place. Buddleja can’t achieve the same effect.
Riparian invasive plants such as butterfly bush have been shown to greatly influence the structure of native floodplain communities, and can even affect physical processes in the river, like hydrology and geomorphology.
Each seed head (the purple cone flower) carries up to 40,000 seeds, meaning each bush can have up to 2 million seeds. The seeds are spread by wind and water, and the plant thrives on disturbed and nutrient-poor soils like the gravel bars of the Dungeness. The bush is a short-lived species, living 30 years at most.
The partners had access to 60 properties, from the river mouth to river mile 11 – and were able to survey and treat more than 100 acres of riparian land, making a large dent in species removal.
After treating the stumps, the crews will be planting native plants such as lupine, willow, cottonwood and alder this fall and next spring.
“We understand that riverside property owners have a unique and often personal relationship with the Dungeness,” Turnbull said. “But restoration efforts such as invasive species removal in the floodplain have long-term benefits to our native fish and wildlife, and can actually improve property values.”