Weed Control in Liriope and Mondo Grass C 867-15

Weed Control in Liriope and Mondo Grass

Figure 1. Creeping lilyturf (Liriope spicata) in flower.

Mark Czarnota, Ph.D., Ornamental Weed Control Specialist
Department of Horticulture, 1109 Experiment Street
Griffin, GA 30223

Liriope and Mondo grass are widely used ground covers in the United States. The two most popular species 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 tends to form tighter vegetative clumps.

Mondo grass is closely related to – and often confused with – Liriope. Dwarf Mondo grass (Ophiopogon japonicus) is the most popular species. When compared to Liriope, Mondo grass tends to have narrower leaves, metallic blue fruits and flowers that are usually tucked into the foliage.

Liriope and Mondo grass have many named cultivars. Both have similar growth requirements and are well adapted to handle a wide variety of growing conditions, including fairly deep shade or full sun. Once established, Liriope and Mondo grass will eventually form a solid cover that is very tolerant of dry conditions. Between planting and establishment, however, weeds may be a problem.

There are many things that can be done to help reduce weed problems. First and foremost is bed preparation. Eliminate all vegetation in a new area with an application of a broad-spectrum herbicide such as glyphosate (e.g., Roundup®) or glufosinate (e.g., Finale®). The bed should then be fertilized with 1 pound of Nitrogen per 1000 ft² and cultivated. After planting Liriope or Mondo grass, a 2- to 4-inch layer of mulch should be applied 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 to 3 inches early in the spring before applying fertilizer and mulch. Preemergence herbicides (Table 1) can also be used at this time to help prevent weed growth.

Some preemergence herbicides are labeled for several species of Liriope (e.g., gigantea, muscari and spicata) or Mondo grass (e.g., japonicus, jaburan and 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, there are several postemergence herbicides (Table 2) that are labeled for use in Liriope or Mondo grass.

As with the preemergence herbicides, most postemergence herbicides are labeled for several Liriope (e.g., gigantea, muscari and spicata) and Mondo grass species (e.g., japonicus, jaburan and planiscapus), but some are not. Read the herbicide label to determine if the Liriope or Mondo grass species in question is on the label. Some postemergence herbicides may require the addition of a surfactant; check the herbicide label. Using an herbicide without a surfactant when one is required will significantly reduce the herbicide’s effectiveness. Spot applications of a systemic broadspectrum herbicide (e.g., Roundup®) may be applied to weeds that are not controlled by these herbicides. Care should be taken to avoid overspray or drift onto Liriope foliage.

Most of the pre- and postemergence herbicides listed in this publication are labeled for both container- and field-grown Liriope, but some are not. Refer to the label to determine if an herbicide is approved for fieldor container-grown ornamentals.

Several herbicides are currently being tested for use in Liriope and Mondo grass, but are not labeled. One of the most exciting is halosulfuron (Sedgehammer®), which provides excellent control of both yellow and purple nutsedge (Cyperus esculentus and C. rotundus) and appears to be tolerated by Liriope and Mondo grass. Note: The use of this herbicide in Liriope or Mondo grass is currently an off-label application.

Unfortunately, both Dwarf Mondo grass and Liriope can creep into turfgrass and become a weed problem. At present, there are no labeled selective herbicides that control Liriope and Mondo grass in turfgrass; however, research at the University of Georgia has shown that metsulfuron (Manor®) provides excellent control of both Liriope and Mondo grass. At present, the only solution is to renovate the infected area by physically removing the Dwarf Mondo grass or Liriope or by treating the infected area with a broad-spectrum herbicide (e.g., Roundup®) and reseed or replant.

NOTE: Trade and brand names are used only for information. Cooperative Extension, University of Georgia College of Agricultural and Environmental Sciences does not guarantee nor warrant published standards on any product mentioned; neither does the use of a trade or brand name imply approval of any product to the exclusion of others that may also be suitable.