The term “monkey grass” is a common, often confusing, name used in horticulture to describe popular evergreen groundcovers that are not true grasses at all. These plants belong to the Asparagaceae family, which is a significant part of the confusion, as they are more closely related to lilies than turfgrass. They are highly valued in both residential and commercial landscaping for their low-maintenance nature and ability to thrive in challenging environments. The popularity of these ornamental perennials stems from their dense, grass-like foliage, which creates a lush, uniform appearance in borders and shady areas.
Identification and Key Varieties
The name “monkey grass” primarily refers to two distinct but similar-looking genera: Liriope and Ophiopogon. While both offer strap-like foliage, they can be differentiated by their leaf width, flower prominence, and growth habit.
Liriope, often called Lilyturf, typically features wider leaves, usually around one-quarter to one-half inch in width, and produces noticeable flower spikes that stand above the foliage. These showy spikes bloom in late summer, displaying purple, lilac, or white flowers followed by black, berry-like fruit. The most common varieties are Liriope muscari (clumping habit) and Liriope spicata, which spreads aggressively through underground rhizomes.
Ophiopogon, commonly known as Mondo Grass, tends to have thinner, finer leaves, often only an eighth to a quarter-inch wide, and generally maintains a more compact, shorter appearance. Its flowers are usually small, white or pale lilac, and often remain hidden within the dense foliage. A notable cultivar is Ophiopogon planiscapus ‘Nigrescens’, which is prized for its striking, nearly jet-black foliage, providing a unique contrast in the garden.
Growth Habits and Landscaping Uses
The growth habit is the most significant factor when deciding where to place these plants in a landscape, as varieties exhibit either a clumping or a running nature. Clumping types, such as Liriope muscari and most Ophiopogon species, form tidy, slowly expanding mounds, making them perfect for precise edging along walkways or foundation plantings. These varieties maintain a fixed boundary and are often used to define the margins of flower beds or lawns. They are also frequently used in containers, where their contained root systems prevent them from spreading.
Conversely, running varieties like Liriope spicata spread rapidly via rhizomes, forming a dense, continuous mat of foliage. This aggressive spreading habit makes L. spicata highly effective for mass planting over large areas or for functional uses like erosion control on slopes and banks. Both genera are remarkably tough, tolerating a wide range of light conditions from full sun to deep shade, though flowering is usually best in partial sun. They also grow well in various soil types, including sandy and clay soils, provided the area is well-drained.
Successful Cultivation and Management
Successful cultivation begins with proper planting, which is best done in the spring or early fall to allow for root establishment before temperature extremes arrive. When planting, the crown of the plant—where the leaves meet the roots—should be set level with the surrounding soil surface. For mass coverage, plants can be spaced closely; for instance, running Liriope spicata can be planted 5 to 15 centimeters apart to achieve a quick, dense groundcover. After planting, keep the soil consistently moist for the first few weeks, though once established, the plants are quite drought-tolerant.
A major maintenance task is the annual pruning of old foliage, which should be completed in late winter or very early spring before new growth begins. Cutting the leaves back to about two to three inches above the ground removes winter-damaged or unattractive foliage, making way for a fresh, lush flush of new growth. Overcrowded clumps of Liriope muscari can be easily divided in the spring by splitting the root ball into smaller sections and replanting them. The most serious issue to avoid is leaf and crown rot, caused by the water mold Phytophthora palmivora, which is promoted by poor drainage and overwatering.