By Mark Czarnota
University of Georgia
The good news is that annual broadleaf and grassy weeds can be easily controlled with mulches and the judicious use of herbicides.
As with any garden plants, planting day lilies in a proper place is vital to growing healthy plants.
Mulches are extremely helpful in preventing weeds from germinating. Always have a 2- to 4-inch layer of pine bark, pine straw or shredded hardwood bark in place.
Many herbicides are labeled for use on day lilies.
Postemergent herbicides
Several postemergent grass herbicides are labeled for use in day lilies: Acclaim Extra (fenoxaprop); Envoy (clethodim); Vantage (sethoxydim); and Fusilade II, Ornamec and Grass-B-Gon (fluazifop).These grass herbicides are concentrates you mix with water and spray over the top of day lilies to control actively growing grasses. They won't keep seeds from germinating.
Pre-emergent herbicides
Pre-emergent herbicides keep many broadleaf and grass weed seeds from sprouting: Barricade and Factor (active ingredient prodiamine); Dimension (dithiopyr); Gallery (isoxaben); Pendulum (pendimethalin); Pennant (metolachlor); granular Snapshot (isoxaben and trifluralin); Surflan (oryzalin); Treflan (trifluralin); and XL (benefin and oryzalin).You can get most of these products in both granular and sprayable form. Granular herbicides are more popular because they require no mixing and are more forgiving when you apply it wrong.
Note that these herbicides don't control all weeds. There are no silver bullets when it comes to weeds. Most of these chemicals or combinations will provide 80-percent to 95-percent control of the weeds from seed.
Some weeds aren't controlled with pre-emergent herbicides, but most of these weeds can be easily hand-removed.
Limitations
The pre-emergent herbicides listed are designed to work only if you apply them before the weeds germinate, and all will need to be applied at least twice (spring and fall).Pre-emergent herbicides tend to be more useful to large growers. In the home garden, you might find hand-removing weeds adequate and even invigorating.
All of these herbicides were available when this article was written. But herbicide labels can change, so make sure that you read and understand the label before using any pesticide.
As herbicides go off patent, many third-party manufacturers may market under different trade names. Glyphosate, the active ingredient in Roundup, is now available from many suppliers.
The tough part
Now, the tough part: Broadleaf and other perennial weeds can be hard to control in day lilies.Nut sedge (Cyperus species) and Florida betony (Stachys floridana) are two problem weeds with no selective over-the-top herbicides available to control them in day lilies.
You can carefully use products that contain the glyphosate to control the problem perennial weeds you can't keep out by hand or with mulches.
To do this, carefully separate the weed foliage from the day lily leaves. Remove as little of the weed foliage as possible, and try not to break any leaves or stems. If you can lay the plant on bare ground or a piece of plastic, do so.
Paint or sponge
Paint on or sponge-apply a 5-percent solution of glyphosate (6 ounces of herbicide to 128 ounces of water). Make sure the product you use to make the solution contains 41 percent or more glyphosate.Be careful not to get the herbicide on the day lilies. If you do, wash it off immediately. Cover the plant with paper or plastic until the herbicide has dried.
In 10 to 14 days, the treated weeds will begin to die. If any begin to resprout, repeat the procedure.
A fairly new herbicide, Manage (halosulfuron), provides excellent control of sedges (yellow and purple). It can be used as a spray around day lilies.
(Mark Czarnota is an Extension Service horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)
