Landscape - Controlling Weeds in Liriope and Mondo Grass Beds

Weed control in ground covers is based on starting with a weed free bed, mulching, and the use of preemergence herbicides. Once weeds emerge in beds, postemergence options are somewhat limited, expecially for broadleaf weeds. The following is information on weed control in liriope and mondo grass beds from the University of Georgia.

Liriope and mondo grass are widely used ground covers in the United States. There are approximately five species of liriope, but the two most popular in the ornamental industry are Liriope muscari (Blue Lily-turf) and Liriope spicata (Creeping Lily-turf). L. spicata has a narrower leaf and tends to spread more aggressively than L. muscari. L. muscari is more common in the south, and is not as aggressive as L. spicata, tending to form tighter vegetative clumps.

There are approximately three species of mondo grass, with the most popular being dwarf mondo grass (Ophiopogon japonicus). Mondo grass is closely related to liriope and often confused with liriope. When compared to liriope, mondo grass tends to have narrower leaves and metallic blue fruits, and flowers are usually tucked into the foliage.

Both liriope and mondo grass have very similar growth requirements, with both genera being well adapted to handle a wide variety of growing conditions. Both liriope and mondo grass can grow in fairly deep shade or full sun, and both are just about immune to drought. Most species of liriope and mondo grass have several named cultivars, and will eventually form a solid cover. When this occurs there is very little need for weed control, but between the time you plant liriope or mondo grass and the time you get solid planting, weeds will be a problem.

Many things can be done to help reduce weed problems. First and foremost is bed preparation. If you are planting into a new area, eliminate all vegetation with an application of a broad spectrum herbicide such as glyphosate (i.e., Roundup®) or glufosinate (i.e., Finale®). The bed should then be fertilized (e.g., 1 lb nitrogen/1,000 ft2) and cultivated.

After planting liriope or mondo grass, apply a 2- to 4-inch layer of mulch to the planting area to help prevent weed growth. Encouraging vegetative growth will help attain a solid cover more quickly.

Both liriope and mondo grass will thrive with at least a yearly application of mulch and fertilizer. If possible, water when soil conditions are extremely dry. To encourage spreading, mow liriope or mondo grass to 2-3 inches early in spring before applying an application of fertilizer and mulch. Preemergent herbicides can also be used at this time to help prevent weed growth; refer to Table 1.


Most of these preemergent herbicides are labeled for several species of liriope (i.e., gigantea, muscari and spicata) or mondo grass (i.e., japonicus, jaburan, planiscapus), but some are not! Make sure to read the herbicide label to determine if the Liriope species in question is on the label.

If weeds have germinated, several postemergent herbicides are labeled for use in liriope or mondograss (Table 2).


As with the preemergent herbicides, most postemergent herbicides are labeled for several species of liriope (i.e., gigantea, muscari and spicata) or mondo grass (i.e., japonicus, jaburan, planiscapus), but some are not! Make sure to read the herbicide label to determine if the liriope or mondo grass species in question is on the label. Some of the postemergent herbicides may require the addition of a surfactant. Check the herbicide label to determine if the herbicide formulation that you are using requires the addition of a surfactant. Using a herbicide without a surfactant, when it requires one, will severely reduce the effectiveness of the herbicide. Spot applications of a systemic broad spectrum herbicide (i.e., Roundup®) may be applied to weeds that are not controlled by these herbicides. Be careful to avoid overspray or drift onto liriope foliage.

Most of the pre and postemergent herbicides listed are labeled for both container and field grown Liriope, but some are not. Refer to the label to determine if the herbicide you are using is approved for field or container grown ornamentals.

Unfortunately, both dwarf mondo grass and liriope can creep into turfgrass and become a weed problem. At present there are no selective herbicides that control dwarf mondo grass or liriope in turfgrass. At present, the only solution is to renovate the infected are by physically removing the dwarf mondo grass or liriope or by treating the infected area with a broad spectrum herbicide (i.e., Roundup®) and reseed or replant.

Information from "Weed Control in Liriope and Mondo Grass" by Mark Czarnota, Ph.D., Ornamental Weed Control Specialist, Department of Horticulture, University of Georgia.