Getting rid of thistle in 3 steps |
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Getting rid of thistle in 3 steps

Q uestion: How can I get rid of thistles in my ground cover? I do not want to kill off my ground cover. It is on the hillside in front of my house. The area is very sunny. Full sun almost the whole day. The ground cover is very thick. It has small, needle-like leaves and is low to the ground. I can’t remember the name of it but it’s very old and took a long time to fill in. Please help. I don’t want to rip it out and start over, but it is beginning to look like my only option.

Answer: Getting rid of any weeds in ground cover is problematic, but thistles present an extra challenge. Not only do thistles spread via seed, their thick, white roots also spread underground, causing new plants to pop up on a regular basis. Weeds that spread in this fashion should never be tilled or the problem will become worse as each root piece the tilling process leaves behind will develop into a new plant.

A few months ago, I wrote a column on how to manage thistles in an empty garden bed, but managing them in a ground cover is a whole different ballgame.

No matter what weed you’re dealing with, when it grows throughout a bed of ground cover, I recommend following these steps.

1. Never let the weed set seed. Whether it’s grass, clover, bindweed, or thistles, it’s important to not let the weed’s flower turn into seed. Doing so will only make the problem far worse. Even if it means you chop down the weeds with a string trimmer or loppers every week or two, it will prevent seeds from being produced. It also weakens the weeds over time, making it easier to control.

2. The second step in controlling weeds in ground covers is to hand pull them religiously. While this task isn’t easy, it’s crucial to controlling the weed population. Even if you don’t get every bit of a weed’s root out, you’ll be weakening the plant, and with repeated top-killing like this, the weed is eventually starved of carbohydrates and dies. It may take a season or two, but going out and weeding the ground cover bed on a weekly basis makes a huge difference.

3. You can also target-apply organic herbicides to the weeds. The brands I most often recommend are Avenger and BurnOut (both of which are available from various online sources, including Amazon and The trick with using these products in ground covers is always to apply it just to the weeds and not to the ground cover itself. These products do not discriminate and will kill any plants they come in contact with. To target the application, put on a chemical-resistant glove and then soak a sponge with the herbicide. Hold the sponge with your gloved hand, and wipe it up the weed, from its base to its top, squeezing the herbicide onto the plant’s leaves and stems. This keeps the herbicide off the ground cover. You may have to repeat this process a few times in order to eliminate all the weeds, but it is very effective.

As with all herbicides, it’s important to follow label instructions carefully. Organic herbicides are often based on acetic acid which can be very caustic to skin, so heed all the precautions on the label.

A combination of all three of these steps, done in a consistent fashion, will clear your ground cover of its weedy visitors.

Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden,” “Good Bug, Bad Bug,” and her newest title, “Container Gardening Complete.” Her website is Send your gardening or landscaping questions to [email protected] or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.

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