Bishops Weed - Ask Extension
Hi, I have an infestation of bishops weed that is in my shady dry clay soil and it is taking over everything, and starting to creep (or race!) into my...
Knowledgebase
Bishops Weed #872483
Asked June 10, 2024, 5:22 PM EDT
Hi, I have an infestation of bishops weed that is in my shady dry clay soil and it is taking over everything, and starting to creep (or race!) into my distraught neighbors yard. I've tried to pull it up, of course to no avail. Can I treat it with Round up or any other chemical? (I have not used chemicals because I had bee hives until last fall). Should I at least be pulling the white flowers off in the meantime? There are ferns and other perennials mixed in with the weed. It's a very large area (my entire "wild" yard), so I don't think I can cover it with cardboard/plastic. Any suggestions? (My neighbor sunk some 8 inch metal barriers to try to stop it, but we don't know if that will work....) It is also growing around some maple trees so there are roots which makes it difficult to dig up. Help!!
Washtenaw County Michigan
Expert Response
Eradicating Bishop's Weed (Aegopodium podagraria) is a challenging, multi-year task. To kill the roots; you must starve them by preventing photosynthesis by (continually) removing all above ground stems.
I'd consider carefully removing the perennials you wish to save, (making sure to remove any bishop's weed root from them before replanting) and then spray the area with the active ingredient glyphosate, which is a non-selective herbicide and will kill all plants it contacts. Around the base of your maple trees you may need to paint it on the leaves to minimize risk to the tree. The barrier your neighbor installed will need to go much deeper to be effective. Mowing low helps as does solarizing the area.
More info in the attached links:
https://extension.umaine.edu/gardening/2022/05/10/removing-bishops-weed/ - a non-chemical intervention approach
https://extension.umaine.edu/gardening/2024/06/05/what-can-be-done-to-control-bishops-weed/ - depth of 'de-fence' info
https://hyg.ipm.illinois.edu/article.php?id=899
https://cipwg.uconn.edu/ci-goutweed/#C - multiple control options
https://plants.ces.ncsu.edu/plants/aegopodium-podagraria/
https://solvepestproblems.oregonstate.edu/property-guides/control-weeds-without-herbicides
I wish you success.
I'd consider carefully removing the perennials you wish to save, (making sure to remove any bishop's weed root from them before replanting) and then spray the area with the active ingredient glyphosate, which is a non-selective herbicide and will kill all plants it contacts. Around the base of your maple trees you may need to paint it on the leaves to minimize risk to the tree. The barrier your neighbor installed will need to go much deeper to be effective. Mowing low helps as does solarizing the area.
More info in the attached links:
https://extension.umaine.edu/gardening/2022/05/10/removing-bishops-weed/ - a non-chemical intervention approach
https://extension.umaine.edu/gardening/2024/06/05/what-can-be-done-to-control-bishops-weed/ - depth of 'de-fence' info
https://hyg.ipm.illinois.edu/article.php?id=899
https://cipwg.uconn.edu/ci-goutweed/#C - multiple control options
https://plants.ces.ncsu.edu/plants/aegopodium-podagraria/
https://solvepestproblems.oregonstate.edu/property-guides/control-weeds-without-herbicides
I wish you success.
Thank you for your detailed response and explanations. I still have a few questions. 1. Should I cut the bishops weed first to eliminate as much of the leafy area as possible and then spray what is left of the stems? And then continue to cut what comes back? 2. You mentioned Glyphosate, which I understand used to be the ingredient in Round Up (and similar products). But I have found it difficult to find any products with Glyphosate now for the home gardener. Would the ingredients in the current Round up do the same as Glyphosate or do I really need to find a product with Glyphosate? Thanks. Karen > On Jun 14, 2024, at 10:05 AM, Ask Extension <ask> wrote: > ></ask>
I would not cut the bishop's weed first as you want to give each plant a good dose of glyphosate. If new sprouts come up they need to be sprayed as well. There is a product online called 'Roundup Precision Gel Weed & Grass Killer' that is a gel that could be hand (in glove) applied to stubborn plants that are hard to kill rather than having to mix spray multiple times.
Points to consider when using products containing glyphosate. First, as with any pesticide, remember to read and follow all labeled instructions. Second, glyphosate is a broad-spectrum herbicide, meaning it will injure or kill other plants contacted during application, so care is needed to avoid green plant material, exposed roots and injured bark of desired plants. Third, glyphosate is relatively safe in the environment when used as labeled. It adsorbs strongly to soil in most cases (i.e., clay & organic matter), allowing even sensitive crops to be planted shortly after application; meaning no carryover issues are expected. Forth, glyphosate alone can take up to 14 days to show full activity under ideal growing conditions. Retreatment of the area may be needed depending on the degree of infestation. Glyphosate is most effective for perennial control in the fall but can be applied anytime the plants are actively growing (temperatures consistently above 50F, when lawns need regular mowing is a good indicator). For woody species, periods of heavy sap flow in the spring may not be effective times to treat. Finally, be sure that the product you chose has only the active ingredient glyphosate or glyphosate + pelargonic acid. Products with additional active ingredients may have other unwanted effects and may delay the planting of other plants in the coming season(s).
I would continue to search for a product containing glyphosate or glyphosate + pelargonic acid. Try looking online as well. Amazon sells products containing glyphosate. MSU Extension does not endorse any retailers or brands.
Points to consider when using products containing glyphosate. First, as with any pesticide, remember to read and follow all labeled instructions. Second, glyphosate is a broad-spectrum herbicide, meaning it will injure or kill other plants contacted during application, so care is needed to avoid green plant material, exposed roots and injured bark of desired plants. Third, glyphosate is relatively safe in the environment when used as labeled. It adsorbs strongly to soil in most cases (i.e., clay & organic matter), allowing even sensitive crops to be planted shortly after application; meaning no carryover issues are expected. Forth, glyphosate alone can take up to 14 days to show full activity under ideal growing conditions. Retreatment of the area may be needed depending on the degree of infestation. Glyphosate is most effective for perennial control in the fall but can be applied anytime the plants are actively growing (temperatures consistently above 50F, when lawns need regular mowing is a good indicator). For woody species, periods of heavy sap flow in the spring may not be effective times to treat. Finally, be sure that the product you chose has only the active ingredient glyphosate or glyphosate + pelargonic acid. Products with additional active ingredients may have other unwanted effects and may delay the planting of other plants in the coming season(s).
I would continue to search for a product containing glyphosate or glyphosate + pelargonic acid. Try looking online as well. Amazon sells products containing glyphosate. MSU Extension does not endorse any retailers or brands.
