Mondo Grass (Ophiopogon japonicus) is a durable, grass-like perennial often chosen for creating clean, defined garden borders or as a dense groundcover. Valued for its evergreen foliage, clumping growth habit, and minimal maintenance requirements once established, it is a popular choice for edging pathways and garden beds. Successfully installing a Mondo Grass border depends on careful planning, proper site preparation, and precise planting techniques. Following a systematic approach ensures the plants establish quickly and form the desired cohesive boundary.
Selecting the Right Mondo Grass Variety and Location
The first step in planning a border is selecting the appropriate variety of Ophiopogon based on the intended visual effect. Standard Mondo Grass (Ophiopogon japonicus) reaches 8 to 16 inches, while Dwarf Mondo Grass (Ophiopogon japonicus ‘Nanus’ or ‘Kyoto’) grows only 2 to 4 inches tall, ideal for a subtle edge. Black Mondo Grass (Ophiopogon planiscapus ‘Nigrescens’) features deep purple-black foliage and grows to about 6 to 10 inches tall.
Mondo Grass prefers filtered sunlight or partial shade for optimal growth, though it tolerates full shade. Note that darker varieties, like the black form, require some sun exposure to maintain their rich coloration and prevent reversion to green. The soil should be moist yet consistently well-drained, as the plant is susceptible to root rot in waterlogged conditions.
Preparing the Border Site for Installation
Once the variety and location are determined, the planting area must be prepared. Mark the intended border line using a garden hose or string to visualize the final shape. Remove all existing weeds, grass, and debris from the marked area, as Mondo Grass establishes slowly and cannot compete with aggressive weeds.
Loosen the soil to a depth of at least 6 to 8 inches to promote root growth and improve drainage. Incorporate organic material, such as compost or aged manure, to enhance fertility and drainage. If the soil is excessively dry, a light pre-watering will help settle the amended soil.
The Step-by-Step Planting Process
The planting process requires attention to spacing and depth to achieve a dense, uniform border. Mondo Grass is purchased in trays or clumps that must be carefully divided before planting. Each division should have a healthy cluster of roots and several leaves, ideally eight to ten, for a robust start.
Spacing determines how quickly the border fills in. For rapid, dense coverage, place plants 4 to 6 inches apart; slower fill-in allows spacing up to 8 to 12 inches. Dig a hole for each division that is twice as wide as the root ball but only as deep as the roots.
The crown of the plant—where the roots meet the leaves—must sit exactly at the soil surface. After placing the division, backfill the hole with prepared soil, gently firming it to eliminate air pockets. Water thoroughly and deeply immediately after planting to settle the soil around the fine roots and initiate establishment.
Post-Planting Establishment and Maintenance
The first growing season requires a consistent watering schedule for establishment. Newly planted Mondo Grass needs regular moisture, requiring watering a few times a week, especially during dry periods. Once established (typically after the first year), frequency can be reduced to about once a week in the absence of rain, as the mature plant exhibits moderate drought tolerance.
Mondo Grass has minimal nutritional needs, especially if the soil was amended during preparation. If growth appears sluggish, apply a light application of a slow-release, balanced fertilizer in the spring to encourage new foliage. The plant spreads slowly via underground runners (stolons), gradually forming a dense mat.
If foliage becomes ragged or brown over winter in cooler climates, trim the old leaves back in early spring before new growth emerges to refresh the border. Regular monitoring for weeds and the occasional division of overly dense clumps every two to three years will maintain the health and vigor of the border.