By Mark Czarnota
University of Georgia

Day lilies, with their beautiful repeating flowers, are among the
most popular perennials throughout the United States.
Unfortunately, weeds can be hard to control in day lilies.
Established perennial broadleaf weeds can be extremely tough.

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.)