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Eco-Answers from the Pros: Help with Bishop’s Weed

Help!! I have bishop’s weed all over my yard. I don’t use pesticides and I’m afraid to use vinegar because I don’t want to kill any surrounding plants. I live in Litchfield hills in the north west corner of Connecticut. I’m looking forward to spring but dreading seeing the bishops weed. I hope you can offer some suggestions. Thank you so much!!

Honestly, this is a tough plant to control with multi-measures. By eliminating herbicide use or more organic vinegar-based applications, you are left with two more traditional options. The first is solarization. If there are large areas that a tarp or sheet of plastic can be laid between existing garden perennials this is an option. I have had the best results with this approach by allowing the plant to fully emerge in the spring, then covering for three weeks. After three weeks remove the tarp and allow the plant to flush new growth for up to 6 weeks, then cover again for 3 weeks. Repeat in the same order for seasons to come. The other option that can be combined with the solarization method is good old-fashioned hand-pulling and weeding. In order for this to be effective, all white rhizomatous roots need to be completely removed from the soil, as a small root fragment will germinate a new plant. Again, repeat in same order for seasons to come.

 ~ Miles Connors, Parterre Ecological Services, Cambridge, MA

I have been dealing with aegopodium podagraria for quite some time on a few properties.  On one there is a bad, longstanding “patch” of about 50-60 feet by 25 ft of the stuff growing under hemlocks. This was hand pulled by a crew of three working half a day. Tools used: scuffle hoes and spading pitchforks. In this instance (which was successful in elimination). There were not many other plants; it was just a mulched border.

I do find that if this weed is present within planted perennial beds or mixed borders and gets a real foothold, then it is nearly impossible to get out. Some of its stoloniferous roots hide within the crowns of things like Deutzia, Iris, other herbaceous plants- real impossible places to get them out from.

I think if found among dense plantings, then you have to make the call to sacrifice (cull out) much of your garden. And, of course, prepare to use a lot of labor getting the weed pulled from open areas.

Sorry, no quick fixes for that problem that I know of.

 ~ Susan Opton, Terrascapes Landscape Design, Needham, MA

Bishop’s weed aka Goutweed is very, very difficult to eradicate due to its aggressive rhizomes which quickly spread in every direction, especially in cultivated soils. The only method that works for me is to smother the entire area where the goutweed is growing with thick black contractor’s plastic for a full year, if not more. A year of sunlight deprivation should kill the foliage and the root system too. Be sure to extend the plastic several feet beyond any visible foliage and dig a trench around the plastic so that you can monitor for any rhizomes trying to grow out from under the sides of the plastic. Unfortunately with this method, you will lose any other plants growing among the goutweed, but do not try to dig up and transplant any desirable plants because even the tiniest piece of goutweed roots present in the rootball soil will spread the goutweed to the new location. Good luck.

 ~ Ellen Sousa, Turkey Hill Brook Farm, Spencer, MA

I understand your call for help! Bishop’s Weed (Aegepodium) is really difficult to eliminate once it gets established. It spreads like crazy – sending out its underground runners in all directions, becoming entwined with any plants’ roots that are in its way.

Hand digging and weeding can be effective in small areas, but only if you are able to get every last piece of root out and then follow up, continuing to hand dig, any time you see a new sprout.

It sounds like you have a lot of it. If you are able to mulch in between desired plants, try  sheet mulching with a layer of newspaper ( black and white only, one section thick soaked in a bucket of water) then a layer of an organic mulch on top like shredded leaves, pine needles, bark mulch , or woodchips.

In tightly planted beds, the only options I see are to renovate the bed. The first step would be to eliminate the bishop’s weed by either sheet mulching with paper or cardboard (as described above) or sheet mulching with plastic: solarization (using clear plastic) or tarping (using dark plastic). These mulches would need to be in place for a number months, most likely an entire garden season to be effective.

Often, I will find that a combination of the above approaches for different areas of the garden is the best solution.

Good luck!

 ~ Sue Storer, Horticultural Services, Holliston, MA

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