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Dumping a Common Source of Invasive Plants on Mercer Island

By Kendall Watson and Lara Elizabeth Vyas
Mercer Island Patch.com
Officials say that any "garden-variety" plants can become noxious weeds in King County when not disposed of properly.

Did you know that the English Ivy — a local gardener's favorite, especially in hanging baskets — is considered a highly noxious weed, can densely cover up a tree and add more than 2000 lbs to the tree canopy?

Such a top heavy tree, especially a deciduous one, is most likely to topple down during a windstorm and cause heavy damage in an urban area — as it did this past winter. And more often than not, say local nature conservation officials, the Ivy got there thanks to a well-meaning but misguided resident trying to recycle the organic material.

Yard waste dumping in parks and open spaces continues to be a problem on Mercer Island and across King County. Many noxious weeds — like the English Ivy and the Yellow Archangel — continue to be dumped in natural areas where they can generate new plants that sprout easily from stem and root fragments.

"This is one of the most common ways that invasive plants and noxious weeds are introduced to our forests," said Mercer Island Natural Resource Specialist Alaine Sommargren

It's an issue that the Mercer Island Parks conservationist is familiar with. Working under Parks Project Manager Paul West, she helped inventory plant species in Pioneer Park in a 2008 Forest Health Survey, which included 33 different types of invasive plants in the park — including English holly, Himalayan blackberry, cherry laurel, English ivy and yellow archangel. Despite a wealth of community volunteers through non-profit conservation groups EarthCorps and Mountains to Sound Greenway to help control the invasive species, the dumping of these plants continues to be a problem.

"When not caught early, these infestations require a huge amount of time and effort to control," said Sommargren.

The invasive weeds smother native understory plants on the forest floor and take over the shrubs and trees. That results in loss of habitat and food sources for native birds and animals.

King County has also taken notice, declaring yard-waste dumping in parks and natural areas a "rampant problem". Garden weeds with seed-heads, seasonal bedding plants and hanging baskets, tree and shrub trimmings are often dumped ‘over the fence’ into the woods.

“People do not realize that plants can spread from stems, roots and seeds in the yard-waste. They think of it as green material that will just rot,” said Sasha Shaw, the education coordinator for King County noxious weed program. This lack of awareness results in bio-pollution of our natural areas.

“Not only do we lose the aesthetic and ecological value of our parks, such dumps attract rats which then becomes a health hazard as well,” she said.

Some unscrupulous landscaping companies try to save money by dumping their yard waste loads in rural areas, she added. Shaw believes that they are mostly ignorant of the severe consequences of their actions. Any kind of dumping is illegal in King County. Shaw encourages people to ‘do the right thing’ and use the services provided by yard waste collection agencies.

The best way to dispose of the garden waste is to put them in curbside yard waste pickup. If curb-side pickup is not available in your area, take it to yard-waste recycling center in Shoreline. For King County, Cedar Grove processes this waste and converts it into dark, nutrient-rich compost - the magic mantra to a healthy soil. More details can be found on King County’s Solid Waste Division website.

Common garden plants that are noxious weeds

As gardeners, we love our plants. Sometimes, unknowingly, we grow plants that can easily escape cultivation and cause havoc in the local environment. Some of these plants are the Butterfly Bush, English and Atlantic Ivy, Yellow Flag Iris, Yellow Archangel, St. John’s Wort and Japanese Knotweed. For complete list of noxious weeds and weeds of concern, refer to 2011 King County Weed List. Even if a garden plant is not a noxious weed, the very botanical nature of some plants like Periwinkle (or Vinca), a vigorous ground cover, can make it highly invasive. It is best to keep them out of natural areas.

How to remove English Ivy from a tree

Ivy mostly spreads by stem and seed. Roots form at nodes on the stem and help the plant adhere to the surface where it spreads. It can climb large trees and densely cover the canopy. Ivy can be removed from such hazard trees though manual control. Dig out and remove all stems from soil contact. Cut and pry the vines from the tree at a comfortable height. Once the lower rooted sections of the plant are removed, the upper part will wither and die. If possible, remove flowers and seed-heads.  Remove the clippings and apply a thick layer of mulch.

How to report a weed infestation

It is easy to identify an area infested with noxious weeds. A swath of a single plant variety would be dominant in the landscape, especially in open park spaces, pasture areas, in and around lakes and rivers, and especially along roads. Shaw and other specialists at the Noxious Weed Program can address your concerns and help identify the weed. Take pictures and fill in the Weed Report form.

Eco-friendly garden practices

“Know what you plant. Plant the right plant in the right place and don’t dump yard waste,” says Shaw. She recommends removing weeds from the garden early in the season when they are small and easy to remove. Use compost and build a healthy soil. Avoid chemicals in your garden and you will have created a safe and healthy environment for you and your family.

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