Weed them out
November 18, 2008
By J.B. Wogan
Lakeshore residents remove invasive plants
This story is the first in a series about attempts to help preserve the environment by fighting invasive plants.
Trip Rumberger handles an unwelcome garden weed in his backyard. Rumberger is one of many Lake Sammamish shoreline residents tending to a significant weed problem in the area. Photo by J.B. Wogan
King County weed control experts say nonnative species are the second biggest factor affecting native plants and animals on the threatened or endangered species list.
Bill Way, a Sammamish resident with property along Lake Sammamish, owns an environmental consulting firm that helps shoreline residents in east King County combat erosion and the spread of noxious or non-native invasive weeds.
“With a waterfront property, it’s a constant battle against weeds,” said Mark Garff, one of Way’s employees and a landscape architect for The Watershed Company. “Every wave that washes up on your shoreline is potentially bringing in a seed or a part of a plant that can land on your shore and can root.”
Garff said such plants are a major problem for Lake Sammamish. Non-native invasive weeds are aggressive, out-of-towners that crowd out native plants, disrupting food chains and the local ecosystem. Those weeds also kill off native plants that serve as stabilizing buffers between land and water, removing a key component to erosion control.
About 42 percent of species on the threatened or endangered species lists are at risk because of non-indigenous species, according to a 2005 Cornell University study.
This study included damaging effects of non-native invasive weeds, but did not distinguish them from other species.
Non-indigenous animals such as nutria, a South American rodent now thriving in Washington, were also part of the study.
The state has laws in place that require public and private property owners to control and reduce the presence of noxious weeds.
While the terms noxious and non-native invasive weeds are often used interchangeably, Garff said there is a nuanced difference. Noxious weeds are weeds designated by an agency as necessary for removal; they are often invasive — or aggressively spreading — weeds, but not always.
One famous example is poison hemlock, which is not invasive, but is toxic to consume. The ancient Greek philosopher Socrates died by eating poison hemlock.
One noxious weed, garden loosestrife, grows along about 40 percent of Lake Sammamish’s perimeter, according to a 2006 King County survey.
Weeds tend to thrive on private properties that do not undergo constant supervision from the city and county, according to Katie Mesick, a King County aquatic weed specialist. Both Lake Sammamish State Park and Marymoor Park have ongoing programs to beat back noxious weeds, including the garden loosestrife.
Mesick pointed out that there are many future ecological impacts of non-native invasive weeds, but their extent and ultimate consequences —whether they will kill off native species and how many and how soon — is unknown.
One weed, butterfly bush, is replacing willows and elders in the wetlands area, and then killing off butterfly populations, she said.
While butterfly bush is a popular food source for butterflies — Mesick said they crave the weed’s nectar — young butterflies, in their larvae stage as caterpillars, cannot feed from the bush.
“Nobody knows the impact on the entire ecosystem,” said Mesick, explaining that wildlife specialists only know small range impacts on a particular species or type of animal.
“For example, if you’re reducing insect larvae populations, what eats those larvae? What birds, what fish? And how are you affecting animals up the food chain?” Mesick asked.
Garff suggested that renewed interest in dwindling salmon populations in the area could, in turn, cast the spotlight on native plant life that directly or indirectly feed those fish.
Many of Sammamish’s non-native invasive weeds arrived in the area through private gardening, according to Steven Burke, a manager for the King County Noxious Weed Program.
Burke said several of the worst weeds, now outlawed for purchase, were in nursery catalogues in the 1950s and 60s. Purple loosestrife, for instance, has vibrant pastel purple petals that appeal to gardeners.
Himalayan blackberry, Japanese knotweed, English Ivy and morning glory are other examples of non-native invasive weeds spreading along the lake’s shoreline.
In spite of those reasons for increased weed control, Trip Rumberger said tending to his backyard weeds was a harrowing process.
“If it wasn’t for these guys, I probably would have shot myself,” said Rumberger, a Watershed Company client who began restoring his shoreline property under direction from the city and county.
Rumberger said he was overwhelmed, “just wading through what you can and cannot plant.”
Rumberger’s plot of land has about a 95-foot strip along the lake.
To remove all invasive and noxious weeds and replace them with native plants would take several weekends, Garff estimated. From there, the labor is the same as any gardening project, requiring regular watering, pruning and sunlight.
As a landscape architect, Garff said his job is to repopulate the area in a way that is still pleasing to the eye.
Some of Rumberger’s native shrubs will grow as high as 10 feet in height, creating shade and better protection for smaller plants. But a clearing without tall shrubs will allow his family to still access the lake and peer out over the water.
“The biggest obstacle is the view,” said Garff. “You have to balance the desire to see the lake with the need to plant plants.”
Reporter J.B. Wogan can be reached at 392-6434, ext. 247, or jbwogan@isspress.com.
You should know
A series of weed control and gardening organizations have published a handbook through Western Washington University called “Garden Wise.” The book serves as a guide on how to use native plants without diminishing the beauty of your garden.
In all, the book addresses 15 invasive weeds including Japanese, bohemian and giant knotweed, butterfly bush, purple and garden loosestrife, and English Ivy. Each invasive weed comes with three native alternatives and descriptions of ideal conditions for the plant.
You can down load a free PDF edition of the book online at www.invasivespeciescoalition.org.
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