Ornamental · Asparagaceae
Black Mondo Grass
Ophiopogon planiscapus 'Nigrescens'
Few plants come this close to true black, and a little sun keeps the blades at their darkest.
Full sun
Every 3–7 days
USDA 6–9
6–12 in · 15–30 cm
Overview
This is one of the few plants whose foliage comes close to true black. The arching, grass-like blades push up a deep green-purple, then darken as they mature to a glossy near-black, and being evergreen they hold that color through every season. For all the grassy look, it is not a grass at all but a member of the asparagus family, native to Japan.
Spreading on short underground runners, it makes a slow groundcover that widens by inches, not feet, staying a low, compact tuft of dark blades. The tidy clumping form sits well at the edge of a path, between stepping stones, or massed along the front of a border where the dark blades read clearly.
Cold-hardy down to 0°F (-18°C) and undemanding once it has settled, it asks little. Give it decent soil, steady moisture, and enough light to keep the blades dark, and the clump holds its form for years.
Care
The short version: give it full sun to part shade for the blackest blades, keep the soil rich and evenly moist but never waterlogged, and tidy away the old foliage in late winter.
Light
Full sun to part shade brings out the darkest blades; pushed into deep shade, the color slips back toward green. In hot regions a touch of afternoon shade is fine.
Water
Keep the soil evenly moist, watering roughly every 3 to 7 days through dry spells. It tolerates drought once established, but steady moisture gives the deepest color and the strongest growth.
Soil
It wants a rich, humusy, well-drained loam on the slightly acidic side, with a pH of 5.5 to 7.0. Compost worked in at planting gives the roots a good start.
Temperature
The clump takes 0°F (-18°C) at the cold end up to about 95°F (35°C), covering zones 6 through 9. The evergreen blades carry through the cold and refresh with new growth in spring.
Humidity
Ordinary outdoor air is plenty, with no number to track. Drainage matters far more than air moisture, since it is soggy ground, not dry air, that does the damage.
Feeding
A light spring feeding with a balanced general-purpose fertilizer or some compost is all it needs. The plant is undemanding, and piling on more does little.
Pruning
It asks very little. Shear off the tattered or winter-worn blades in late winter before new growth pushes up, and the clump returns fresh.
Repotting
In a container, lift and divide it every 2 to 3 years before the roots crowd the pot. A thinning center or growth that has slowed tells you the time has come.
Size & spacing
Each clump reaches 6 to 12 inches (15 to 30 cm) tall with a spread of 8 to 12 inches (20 to 30 cm). Set them a foot apart for distinct clumps, closer for quicker cover.
When to plant
A hardy perennial for zones 6 through 9 that stays put once planted. Setting it out in spring hands the clump a full season to settle in, and small bell-shaped flowers open through summer, from July into August.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring
- Harvest: summer (July to August)
Hardiness
USDA hardiness zones: 6–9
Temperature: down to -23°C
Troubleshooting
This is an easygoing plant, and almost every problem traces back to one of two things: too much shade or too much water. The earliest signs read right on the blades and the roots.
Yellowing leaves and a clump that rots in wet soil
Soil that sits saturated at the roots brings on root rot. The first sign shows on the blades, which yellow and flop as the damage spreads, and a clump lifted from the wet ground reveals roots gone soft, dark, and mushy. Work grit or compost in to open the drainage, ease off the watering, and replant only healthy divisions into free-draining ground.
Fix:
- Improve drainage by amending soil with organic matter or grit
- Reduce supplemental watering when soil stays wet
- Replant healthy divisions in a better-drained, raised, or amended site
Weak, slow regrowth after dividing
A slow grower recovers slowly. Fresh divisions can sit with barely a new blade for a stretch after replanting, which is the plant settling rather than failing. Split clumps in spring so they have the whole season to root before cold sets in, keep the soil evenly moist while those roots take hold, and give them time instead of digging them up again.
Fix:
- Divide in spring so plants have the full season to re-establish before winter
- Keep soil evenly moist while new roots form
- Allow extra time for recovery rather than disturbing again
Slow to spread and fill in as a groundcover
Slow fill-in is simply this plant's nature. It creeps outward on short underground stolons, so a clump widens by inches each year and takes several seasons to knit its dark blades into solid cover. A sparse, gappy spacing early on is normal, not a fault. Setting plants closer, about 4 in apart, draws the cover in sooner, and splitting established clumps gives you extra plants to tuck into the bare patches.
Fix:
- Be patient and allow clumps to establish over several seasons
- Plant more closely (about 4 in apart) when a faster groundcover effect is wanted
- Divide established clumps to make more plants and fill gaps
Black leaves washing out toward green
The near-black color is driven by sun. Drop the plant into deep shade and the arching blades lighten, sliding back toward an ordinary green that loses all the drama. Move it to a brighter spot and the dark returns to the new growth. In hot regions a little afternoon shade does no harm, but the blades hold their darkest tone where they catch real light.
Fix:
- Move or transplant to a brighter, sunnier location
- In warm climates provide some afternoon shade but otherwise favor sun for color
Ragged, chewed leaves with slime trails
Irregular holes, frayed edges, and shiny slime trails along the blades point straight to slugs and snails, which come out to feed at night in damp, shaded corners. Pick them off by hand after dark, rake away the leaf litter and any cool hiding spots they shelter under, and reach for a slug control only where the chewing keeps building.
Fix:
- Hand-pick slugs and snails in the evening
- Remove debris and reduce excess moisture and hiding spots
- Use slug controls where pressure is heavy
Toxicity
It is not toxic. The plant sits in the asparagus family, not among the dangerous true lilies it is sometimes mistaken for, and the worst case is a mild stomach upset from eating a lot. Safe for homes with pets and children.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat that nibbles a few of the dark blades may get a brief upset stomach, the same as with any plant eaten in quantity.
Dogs None
The grass-like blades carry no known toxin, though a big mouthful could leave a dog briefly queasy.
Horses Safe
The blades hold none of the poisons of the true lilies this plant is so often confused with, so horses are not at risk.
Rabbits Safe
Nothing in the dark foliage is poisonous to rabbits; an occasional bite of the blades does no harm.
Livestock Safe
The foliage holds none of the compounds that trouble grazing animals, so livestock are not at risk.
Birds Safe
Poultry can pick at the blades and the small fruit without concern.
People Safe
Handling the blades poses no risk, and a stray taste does nothing beyond the mild upset any non-food plant might cause.
No special handling required; as with any plant, discourage pets from eating large quantities to avoid mild stomach upset.
Varieties
A handful of selections and look-alikes share the mondo grass name. Leaf color, where the flowers sit, and fruit color are what tell them apart.
Ophiopogon planiscapus 'Nigrescens'
The standard black mondo grass, its arching grass-like blades pushing up green-purple and maturing to a glossy near-black that ranks among the darkest foliage of any perennial.
'Black Dragon' / 'Ebony Knight'
Trade names sold for the same near-black foliage carried by 'Nigrescens'.
Ophiopogon japonicus (green mondo grass / dwarf lilyturf)
The plain green-leaved species, its blades narrower than those of Liriope, its flowers tucked down out of sight in the foliage, and its fruit blue rather than black.
Black-leaved Liriope (lilyturf)
A separate genus, Liriope, with broader leaves, flowers lifted on upright spikes above the foliage, and black fruit instead of the blue of green mondo grass.
Companions
Plant near
Chartreuse or gold-foliage plants (e.g., golden creeping Jenny, Hakone grass 'Aureola'): Bright lime/gold foliage gives strong color contrast against the near-black leaves.
Silver or gray foliage plants (e.g., lamb's ear, dusty miller): Silver tones highlight the dark foliage for dramatic contrast in borders and containers.
How to propagate
There is one reliable way to make more of it, and it keeps the dark blade color true every single time.
DivisionEasy
Spring · One growing season
Division is the only reliable route, since seed will not come true to the dark color. A clump split in spring holds its glossy near-black blades exactly and gets the full season to root in, taking roughly one growing season to settle and fill out.
Myths
Black mondo grass is a true grass.
It only plays the part. This is no grass at all; it is Ophiopogon planiscapus, a member of the asparagus family that happens to grow in a low, evergreen clump of narrow arching blades that read as grass to the eye.
It is the same plant as green mondo grass or lilyturf.
The three are constantly mixed up but stay distinct. Black mondo is its own plant: green mondo grass is the related Ophiopogon japonicus, while lilyturf is the separate genus Liriope with broader leaves and flower spikes held up above the foliage; black mondo's narrow blades and hidden flowers set it apart.