Mondo grass (\(Ophiopogon\) \(japonicus\)) is a popular perennial groundcover used as a turf alternative or edging plant. Although related to the lily, it is characterized by its clumping habit and narrow, evergreen leaves. Its dense growth makes it a desirable, low-maintenance feature. However, the maintenance of this slow-growing plant differs significantly from turf grass, especially regarding regular trimming or mowing.
The Necessity of Mowing Mondo Grass
Routine mowing is generally not necessary or recommended for the long-term health or aesthetics of mondo grass. Unlike turf grasses, mondo grass is a slow-growing plant that maintains a consistent height of 6 to 12 inches. Regular cutting disrupts the natural arching form of the leaves, resulting in a ragged appearance. Mowing should be reserved only for a specific, infrequent purpose rather than standard maintenance. The primary reason to use a mechanical cutter is as a rejuvenation technique to aggressively clean up a large patch of groundcover. This removes widespread winter damage or old, tattered foliage that accumulates over several years.
Performing a Rejuvenation Cut
A rejuvenation cut should only be performed when the foliage is noticeably damaged or severely discolored, perhaps every two to three years. The timing of this aggressive trim is the most important factor to ensure the plant recovers quickly. The cut must be done in late winter or very early spring, before the plant begins to push out new growth for the season. When cutting an expansive area, a rotary lawn mower can be used, but the blade must be sharp to ensure a clean cut rather than tearing the foliage. Set the mower deck to its highest possible setting, aiming to leave at least two to three inches of foliage remaining above the crown. Cutting below two inches risks damaging the plant’s growth point, which can severely stunt its recovery. For smaller patches, a string trimmer or sharp shears are more precise tools. The goal is to remove the old, dead material to allow sunlight and air circulation for the fresh foliage. Immediately after cutting, all debris should be raked away, as leaving clippings can smother new shoots and create conditions for fungal disease.
Year-Round Maintenance Practices
Once established, mondo grass is a low-maintenance groundcover that requires minimal intervention outside of the occasional rejuvenation cut. Proper watering is important, especially for newly planted patches, which need consistently moist soil to establish a robust root system. Mature plants are moderately drought-tolerant but benefit from deep, infrequent watering during dry spells to keep the soil damp, preventing root rot. Mondo grass is a light feeder and requires very little fertilizer, especially when planted in soil rich with organic matter. If a boost is desired, a single application of a balanced, slow-release shrub and tree fertilizer in early spring is sufficient. Applying fertilizer after the rejuvenation cut encourages fresh, healthy foliage. Weeding is most important during the initial establishment phase, as mondo grass is slow-growing and can be easily overcome by aggressive weeds before it forms a dense mat. Over many years, individual clumps may become overcrowded, necessitating division rather than mowing to manage density. To divide, dig up a clump in the early spring and separate it into smaller sections, each with a healthy root mass, before replanting.