Our home in Seattle came with a large number of established Yucca plants, and we would like to get rid of them. However, they are quite stubborn. We've tried a few things, including digging them up, but the root system seems quite deep and extensive and they
always come back, and quickly! Any suggestions? I've thought they were non-native, but I guess they could be the sort that are found in eastern WA. Are there invasive species here in western Washington?
As you have observed, Yucca is very difficult to eradicate completely.
Most of the literature on the subject suggests using herbicide, but even
this may be ineffective, which makes the risk of using harmful chemicals
to control the plant seem even less worthwhile. There are quite a few
informal discussions on how to get rid of this plant on various online
gardening forums, and one mentions local gardening expert Ciscoe Morris's
method for getting rid of unwanted Yucca:
"...he cut it back to ground level and put a couple of squares of heavy
cardboard over it, piled on some compost/bark to hide the cardboard. I'm
not growing yucca, but he said it really worked for killing it without
breaking your back. Leave in place for a year."
The technique described here is called sheet mulching. This involves
laying down overlapping layers of cardboard and then covering thickly
with leaves, compost, and other materials. Agroforestry.net offers information on how to do this. StopWaste.org provides additional helpful information.
Here is an excerpt from an answer to a question similar to yours, written
by one of my colleagues here at the Miller Library:
"The general idea is you spread out a layer of cardboard or newspaper
(about 4-6 sheets) and then cover that with a layer of organic mulch
(compost, straw, alfalfa hay--available at feed stores, wood chips,
coffee grounds, etc.). Then wait 6-8 months. This is not an exact science because there are many variables, such as thickness of newspaper, type of mulch and what type of plant you're trying to kill. Perennial weeds and especially coarse grass will push
through the cardboard once it starts to break down so it is critical that
if and when this happens you pull the mulch back and put down more
newspaper/cardboard, and then replace the mulch."
Yucca is not (yet) considered invasive in our state. Here are links to
information on locally noxious weeds.
Washington Invasive Species Coalition.
King County's Noxious Weed Control Program.
Season
All Season
Date 2007-07-11
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