Weeds and grass in lillies of the valley

Asked May 1, 2017, 2:23 PM EDT

I have very large bed of lillies of the valley. It has a lot of grasses and weeds that have invaded.(see photos) is there a weed killer I can use that will not harm them. If not any suggestions?

Sibley County Minnesota weeds horticulture

2 Responses

Thank you for the question. Weed killers either kill all plants, just grassy weeds, or just broad leaf weeds. The weed killer you select depends on what type of weed you need to control. To complicate matters further, you need to identify the weeds you have in order to choose a chemical post emergent herbicide appropriate for use in a garden (not lawn). From the photos, I see a grass of some sort and creeping Charlie and maybe a few other things. It will be a challenge to selectively kill grass and other weeds and not harm the lily of the valley. For creeping Charlie you need a product that contains triclopyr for best results but it may also kill your lily of the valley. Read the triclopyr label to find out what plants besides creeping Charlie are affected by it. You will have to be vigilant and watch for stragglers that need hand pulling if you are successful with chemical control. Information can be found here on controlling creeping Charlie:

It's harder to choose the right product for the grassy weed because we don't know if it's annual or perennial. You may be able to identify it by using our weed identifier tool that also links to control measures: http://www.extension.umn.edu/garden/yard-garden/weeds/. You have a large area and could try hand pulling the grass, and then spot treat areas with a non-selective herbicide like Roundup but be careful with this product as it will also kill your lily of the valley and anything else it touches.

In short, there is no easy answer to your problem and you will have to be continuously on the watch for weeds once you get them under control.

Thank you for contacting Extension.

Hello,
Another Expert mentioned a personal strategy that was helpful in a situation like yours. He applies a 3-4 inch layer of leaves to the garden in the fall. In the spring, the lily of the valley come up through the leaves but the weeds cannot.