Monkey Grass Plant Profile

Three Types, Three Different Uses

Close up of black monkey grass used in a landscape

David Beaulieu

"Monkey grass" is a common name heard most often in the South. It can refer to any of three different plants: one type of Ophiopogon (black mondo grass) and two types of Liriope. While they're used in similar ways, there are important differences among these three perennials that you should be aware of before making a selection. All are good substitutes for shade-tolerant, semi-evergreen ornamental grasses. All have few pest and disease problems, but you may need to protect them against slugs.

Black Mondo Grass

Black mondo grass (Ophiopogon planiscapus 'Nigrescens') isn't a true grass; true grasses belong to the Poaceae family. Black mondo grass is, instead, a tuberous-rooted perennial in the lily family. It's a stemless plant on which the leaves sprout from the ground in clumps. In summer, a single flower stalk sprouts, carrying small, bell-shaped, pinkish flowers. This grass-like plant is often used as a ground cover for semi-shady areas, or in the front of a border or as an edging plant. It's common in rock gardens and valued for its unusual, black foliage. It makes for a great contrast with a plant like Sedum rupestre 'Angelina'.

Black mondo grass is slow-growing and even slower to germinate, taking up to three months or to more to sprout from seed. It's best to plant it in spring to ensure solid establishment before the first winter.

Botanical Name Ophiopogon planiscapus 'Nigrescens'
Common Names  Monkey grass, black mondo grass
Plant Type Herbaceous perennial
Mature Size 9 to 12 inches tall and wide
Sun Exposure Full sun to part shade
Soil Type Moist, well-drained
Soil pH 5.5 to 6.5
Bloom Time July to August
Flower Color Pink
Hardiness Zones 6 to 9
Native Area Japan

How to Grow Black Mondo Grass

Space plants 4 inches apart in moist, well-drained soil. Immediately top-dress them with compost to retain soil moisture. No seasonal feeding is needed. Each spring, remove old foliage from around the plants. Where you want to thin the plants or propagate them, lift and divide the roots in spring.

Light

Black mondo grass tolerates a wide range of sun conditions, but the warmer the climate, the more shade is of benefit.

Soil

This plant prefers moist but well-drained soil with ample organic material. The ideal pH is somewhat acidic.

Water

Mondo grass must be kept consistently moist but not soggy. The hotter the temperature, the more water is required.

Temperature and Humidity

Ideal growing conditions are warm but not hot. It tolerates a wide range of humidity levels if the soil is kept moist. Slugs are a problem in moist climates.

Fertilizer

Black mondo grass doesn't require much feeding. A single topdressing of compost in the spring will suffice.

Propagating Black Mondo Grass

Black mondo grass is propagated by dividing the fibrous roots in spring: Pry the plant clumps from the ground with a garden fork, then use your hands to tease apart groups of roots, dividing them into sections, each containing a few leaves. A knife may be necessary if the roots are thickly entwined. Cut away any dried or diseased portions of roots. Replant the clumps 4 inches apart in the garden. If you cannot plant them immediately, keep them moist until planting.

Creeping Liriope and Big Blue Lilyturf

Liriope, another genus commonly known as monkey grass, includes two species: creeping liriope (Liriope spicata) and big blue lilyturf (Liriope muscari). Liriope has a very similar growth habit and slow growth rate to black mondo grass, but it's a slightly taller plant. Spring is the best time to start new plants or transplants, when the plant is dormant and there's more moisture to keep the plants from drying out.

Creeping liriope is slightly hardier than big blue lilyturf, so it can be a better choice for northern gardeners. Its blade-shaped leaves are narrower than big blue lilyturf's. Both plants produce flower spikes, but those on big blue lilyturf are showier because they extend above the plant's foliage and are visible from afar.

Creeping liriope received its common name from the fact that it spreads via underground rhizomes. By contrast, big blue lilyturf forms well-behaved clumps. Because creeping liriope can easily spread out of control under the right conditions, it is not well-suited for use as an edging plant. But this same quality makes it a great ground cover for spots where you want a plant that takes over and suppresses weeds or prevents erosion.

Botanical Name Liriope spicata (Creeping liriope), Liriope muscari (Big blue lilyturf)
Common Names  Monkey grass, creeping liriope, big blue lilyturf
Plant Type Herbaceous perennial
Mature Size 9 to 18 inches tall and wide
Sun Exposure Full sun to part shade
Soil Type Average, well-drained
Soil pH 6.0 to 7.0
Bloom Time August to September
Flower Color Lavender
Hardiness Zones 4 to 10 (Creeping liriope); 5 to 10 (Big blue lilyturf)
Native Area China, Japan, Southeast Asia

How to Grow Creeping Liriope and Big Blue Lilyturf

Space these plants 12 to 18 inches apart; they'll quickly fill in gaps. Poor soil should be amended with compost. Feeding is rarely necessary; an annual top-dressing of compost may be helpful. Once established, water the plants deeply once a week. Where division is necessary to thin out dense clumps or propagate plants, do it in the early spring. The foliage can be mown down with a lawnmower set at a high cutting length when the growing season is over (in warmer climates, the plant may be evergreen).

Light

Liriope tolerates a wide range of sun conditions, but in very warm climates, some shade is beneficial.

Soil

These plants prefer an average, well-drained soil that has ample organic material. The ideal pH is slightly acidic to neutral, with a pH between 6.0 to 7.0.

Water

Liriope performs ideally if it receives a good, heavy watering each week, but once established it has good drought-tolerance.

Temperature and Humidity

Ideal growing conditions are warm but not hot. These plants tolerate a wide range of temperatures and humidity levels.

Fertilizer

Creeping liriope and big blue lilyturf are light feeders and do not require much fertilizer. Amending the soil with a topdressing of compost often is all you need. Alternatively, you can apply a slow-release shrub food, also in spring. Over-feeding can make the plants more susceptible to disease and other problems.