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Search Results for: Invasive plants--Control | Search the catalog for: Invasive plants--Control

Plant Answer Line Question

Keywords: Hedera hibernica, Hedera helix, Invasive plants--Control, Noxious weeds--Washington

I am trying to write a letter about English ivy in order to get it removed from a public library. Is it a noxious weed?


Washington State and King County noxious weed information is updated annually. Currently, three cultivars of Hedera helix and one cultivar of Hedera hibernica are Class C Noxious Weeds in the State of Washington.

Here is the link to descriptions of these four types of English ivy.

Class C Noxious Weeds are weeds that are already widespread; removal is NOT required by law. However, individual counties can adopt removal programs as they see fit. Here is the complete list of Class C noxious weeds in Washington. Here is the page specifically about ivy.

King County also has more information on a website about noxious weeds.

King County does not require control or eradication of any of the four English ivy cultivars. Although control is strongly recommended, it is not required.

Date 2018-06-14
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Plant Answer Line Question

Keywords: Hedera helix, Invasive plants--Control

In trying to eradicate English Ivy I am considering using Clorox on the roots. I have cut off all of the leaves. Is this safe and do I need to guard against nearby roots from trees that I want to save? If the Clorox will work I am assuming that I would use it undiluted for maximum effect. Any other ideas on English Ivy eradication?


Ivy is a tough plant to eradicate, as I imagine you already know. The resources I have consulted indicate that manual removal methods are more effective than chemical methods. Ivy apparently has an excellent defense system against chemicals. I could find nothing in the literature that suggested using bleach to kill the roots of Hedera helix (English ivy).

Here are links which may be of use to you.

From King County Noxious Weed Control.

From Portland, Oregon's No Ivy League.

Local garden writer Ann Lovejoy's article in the Seattle Post-Intelligencer. Excerpt:

"Why not just poison it? Using herbicide on ivy is both futile and dangerous. Ivy's waxy foliage repels herbicides, which run off to damage nearby plants and pollute water systems.

"To safely and steadily get rid of ivy, begin by cutting all vines that have scrambled up trees or posts. Remove as much as you can reach from each trunk. If you miss a few stubborn scraps here and there, don't worry about it. Just be sure that none of the vines remain uncut or are left dangling.

"Now remove all ivy at ground level by pulling strands and prying roots with a small hand-mattock or hori-hori (Japanese farmers' knife). Even if you miss a few roots (as you will), they won't all sprout back.

"Finally, mulch with a combination of woodchips and compost if you plan to replant soon. If you just want to keep the ground clear for a while, use coarse wood chips for mulch.

"To keep the mulched area clear, check it two or three times a year. You can quickly remove any new shoots that appear, along with as much root as possible."

Date 2018-05-04
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Plant Answer Line Question

Keywords: galls, Cytisus scoparius, Rosa nutkana, Insect-plant relationships, Invasive plants--Control

I work on a restoration site and this fall I have been noticing weird fuzzy growths on many of the Nootka roses (Rosa nutkana) growing there. Do you know what is causing this? And is it related to similar strange growths on all of the Scotch broom? In the case of the broom, it actually kills them completely—they turn brown or black, and their roots are pretty much non-existent, which makes them very easy to uproot (which is what we are trying to do). I just don’t want to lose the roses or other desirable plants on the site.


What you are describing on the roses sounds like mossy rose gall (Diplolepis rosae). Washington State University Extension's HortSense page says that these galls which are caused by cynipid wasps will not harm the host plants. You could picky them off the roses, but that seems impractical in a restoration site, and besides they are fairly benign and attractive curiosities. The particular species of cynipid wasps which cause it are unlikely to affect plants which are outside the rose family.

Your other question about dying Cytisus scoparius (Scotch broom) is especially interesting. I think what you are seeing on those browned and blackened plants is also a gall, caused by the Scotch broom gall mite (Aceria genistae). This insect is apparently on the cutting edge of controlling invasive broom. According to this informational page from University of California Statewide Integrated Pest Management Program, the mite was first seen on broom plants in Tacoma, WA and Portland, OR in 2005. It has since spread through the Pacific Northwest. An abstract of an article entitled "The Scotch Broom Gall Mite: Accidental Introduction to Classical Biological Control Agent?" (J. Andreas et al.) appeared in the 2011 XIII International Symposium on Biological Control of Weeds. Studies are underway to see if the mite affects non-target plants such as lupine. For now, you can rejoice in the fact that the mites are curbing the growth and reproduction of the broom, and making your work a little bit easier!

Date 2017-11-03
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Garden Tip

Keywords: Invasive plants--Control, Weed control

Weed fact sheets are available from UC Davis, in cooperation with the Nature Conservancy. This is an excellent resource for learning how to control some of the most tenacious invasive plants in the US. Many weed profiles have color pictures, "success stories," and references to research.

Date: 2007-07-13
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May 31 2018 13:14:08