You may find one of two kinds of monkey grass aping each other in gardens — lily turf (Liriope spp.) and mondo grass (Ophiopogon japonicus). Although they share a frequent name, the sizes, shapes and growth habits of those grassy lily plant family members have different spacing requirements.
Lily turf and mondo grass are commonly mistaken for one another, however on second glance, their differences are apparent. At U.S. Department of Agriculture plant hardiness zones 7 through 11, mondo grass is an appropriate ground cover for shady places. The leaves, which resemble grass, curve backward. The two primary lily turf species possess distinctive development habits. Big blue lily turf (Liriope muscari) grows in clumps across its perennial range in USDA zones 5 through 10, while collapsing lily turf (Liriope spicata) spreads as a ground cover in USDA zones 4 through 10.
Clumping Monkey Grass
Because blue lily turf includes a 1-foot spread, space plants 12 inches apart to produce a continuous edge around flower beds or islands. Some newer cultivars are improved variations of their species, like “Cleopatra” (Liriope muscari “Cleopatra”), a perennial in USDA zones 5 through 9. “Cleopatra” has dark green leaves and grows 24 inches tall, when compared with a maximum height of 18 inches of their species. Space “Cleopatra” further apart — 15 ins — to adapt its mature spread, rather than the standard 12-inch spacing of their species. At USDA zones 6 through 11, “Silvery Sunproof” (Liriope muscari “Silvery Sunproof”) is ranked by many nursery growers as the top variegated liriope cultivar due to its suitability for sunny or shady places, and because it’s the maximum concentration of white coloration of their variegated cultivars. Space “Silvery Sunproof” 12 inches apart to adapt its 1-foot spread.
Spreading Monkey Grass
Although blue lily turf keeps a tidy clumping habit, creeping lily turf may aggressively invade your lawn due to the way it grows. It spreads by rhizomes, which are modified stems that form an underground network of continuous growth. Because creeping lily turf forms a carpet of greenery, it excels as a dense ground cover. But it lacks the restraint of blue lily turf, which makes it unsuitable as a border plant for flower beds or islands. To naturalize massive places or stabilize slopes, space creeping lily turf plants a minimum of two feet apart because every plant’s mature spread may reach 24 inches.
Shady Monkey Grass
Mondo grass is sometimes called “little monkey grass” as compared to lily turf, it does not grow quite as tall and its leafy blades are thinner, typically just 1/8 inch wide. In shady places in which it’s a challenge to grow grass grass, mondo grass is a suitable alternative. You can also use it to border trails and edge flower beds. Space plants 12 inches apart, and they will grow together to form a good mat.