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Grassy Weeds in Daylilies

Quackgrass is the ultimate challenge!

By: Sandy Feather 2008
Penn State Extension

Q. Our daylily bed is overrun with Quackgrass.  We have tried repeated hand weeding of this white-rooted spreading grass, but it keeps coming back. Do you have any suggestions for getting rid of Quack grass?
A. For those of you who have never had the pleasure of dealing with quackgrass (Elytrigia repens), it one of the most difficult weeds to manage. It spreads by tough, pointed underground stems (rhizomes). Any little piece of rhizome left behind will grow into a new plant. Quackgrass rhizomes often grow right through the fleshy roots of plants such as daylilies. Fluazifop-P-butyl, which is sold under trade names such as Ortho's Grass-B-Gon or PBI Gordon's Ornamec, is labeled to remove quackgrass from daylily beds.  

Selective Herbicides for Grassy Weeds

A selective herbicide that kills grassy weeds without damaging broadleaf plants, it is most effective in spring or early summer when quackgrass is actively growing and not more than 6-10 inches tall. You may still get some control by applying it in late August or early September. At that time of year, plants are moving the carbohydrates produced through photosynthesis down to store in their roots so they have enough energy to push new growth next spring. Late summer and early fall is the best time to kill many troublesome perennial weeds.

Weeds in juniper ground cover
Grassy weeds are challenging in ground covers like these spreading junipers. This homeowner has the "triple-whammy" -- fighting grass plus wild onions and thistles!

Other Options for Daylilly Plantings

You also have the option of lifting all your daylilies in mid-September. Inspect their roots for quackgrass rhizomes and remove any that have grown through. Then you can pull or dig the remaining quackgrass plants from the bed and replant your daylilies. Instead of digging it out, you can spray the quackgrass left in the bed with Roundup (glyphosate), a non-selective, systemic herbicide that kills most plants. It takes two weeks for Roundup to thoroughly kill weeds, roots and all, so you would have to wait to replant your daylilies. If you disturb weeds that have been sprayed with Roundup prematurely, it may not have a chance to kill the roots completely.
Whichever approach you take, do not be surprised if you see some re-sprouts next spring. You can spot treat them with Grass-B-Gon or pull them out by hand. The trick with hand weeding is to stay on top of it. You can exhaust a weed's root reserves if it doesn't exhaust you first!


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