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Ask the Gardener: How to win the battle vs. goutweed

Goutweed quickly spreads underground, and trying to weed the white roots only breaks them off.

Goutweed spreads quickly underground. Adobe Stock

What to do this week Keep watering, following any restrictions in your municipality. Look around and learn to recognize when plants are begging for water with drooping, curling, or browning leaves, and prioritize watering those plants. Plant seeds of short-season vegetable crops that will thrive in the coming cool weather such as lettuce and radish as space becomes available in your garden. Water the soil before weeding or pulling out spent vegetable plants so the roots slip out easily with minimal soil disruption. Stop deadheading and fertilizing roses so the shrubs can prepare for dormancy.

Q. I have a large perennial bed that was overrun with goutweed when I was ill, and it also has deer ticks, as it borders a wooded area. I’d welcome your advice on how to eliminate the goutweed (and ticks) and also want to note that I have a vernal pool nearby. We care for our yard organically, using no herbicides and only biologic pesticides. Is this situation hopeless?

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V.N., Beverly

A. Goutweed quickly spreads underground, and trying to weed the white roots only breaks them off, with each piece growing a new plant. Most people spray goutweed (Aegopodium podagraria) with glyphosate when it is in active growth in the spring after shuffling and walking on it to bruise the leaves so the sap is exposed. Since you are gardening organically, I would recommend just cutting all the garden top growth down to less than an inch in height and bagging it for your town’s composting collection. Next, cover the affected ground with impermeable plastic to solarize the roots and deprive them of sun and water. Extend the tarp 3 feet beyond the edge of the goutweed, use rocks or mulch or even potted plants to hold it down, and wait a year or two.

If you are determined to save your perennials, dig them up ahead of time and move them into pots for three months. Check for any goutweed sprouts before replanting them. However, I would not try to save the perennials that have already been overtaken, as their roots have probably been contaminated by tiny bits of goutweed roots. I would just sacrifice them. Such easy contamination by a tiny bit of root is why I try not to buy top soil or even potted plants at community sales that were dug up from strangers’ gardens. It is not worth the years of weeding headaches that can result from a tiny piece of errant goutweed root. I saw goutweed advertised by a big-box store, so there are still people selling this!

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To weed out goutweed by hand, you need to dig out all the soil to a depth of 18 inches and sift it through a sieve with half-inch openings to try to remove every tiny piece of root. This is slow-going! Another alternative would be to dig a trench around the outside of the entire goutweed-infected area and insert metal or plastic edging to a depth of 8 inches or more to discourage the underground goutweed roots from spreading any farther. Then regularly mow the area around the goutweed to keep it from spreading by denying it photosynthesis. You write that there is a wooded area and a vernal pond nearby. Goutweed is capable of environmentally overrunning and destroying these natural areas.

Regarding your question on ticks, I spray my gardening clothes with Sawyer permethrin insect repellent to keep ticks away, and I tuck my pant legs into my socks. I don’t spray it on my skin.

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