Ornamental · Asparagaceae
Black Mondo Grass
Ophiopogon planiscapus 'Nigrescens'
Few plants come this close to true black, and a little sun keeps the leaves their darkest.
Full sun
Every 3–7 days
USDA 6–9
6–12 in · 15–30 cm
Overview
Black mondo grass is one of the rare plants with foliage that reads as near-black, which is why designers reach for it again and again. The arching, grass-like leaves start out a deep green-purple and darken as they mature, holding their color through the year as an evergreen perennial. It isn't actually a grass at all but a member of the asparagus family, native to Japan.
It earns its keep as a slow, well-behaved groundcover. Spreading on short underground runners, a clump enlarges by inches rather than feet, so it never bullies its neighbors the way faster spreaders do. That restraint makes it easy to place along a path edge, between stepping stones, or massed at the front of a border where the dark leaves can do their work.
The plant is tough where it counts. It shrugs off cold down to 0°F (-18°C), asks little once it has settled in, and stays handsome with almost no fuss. Give it decent soil, steady moisture, and enough light to keep the leaves dark, and it holds its own for years.
Care
The short version: give it full sun to part shade for the blackest leaves, keep the soil rich and evenly moist but never waterlogged, and tidy up old foliage in late winter.
Light
For the darkest leaves, give black mondo grass full sun to part shade. Plants left in deep shade drift back toward green, so favor a brighter spot, though a little afternoon shade helps in hot regions.
Water
Keep the soil evenly moist, watering it roughly every 3 to 7 days in dry spells so it never bakes dry. It turns drought tolerant once established, but steady moisture brings the best color and growth.
Soil
Plant it in rich, humusy, well-drained loam on the slightly acidic side, with a pH of 5.5 to 7.0. Work in compost at planting to feed the roots and help the bed hold moisture without staying soggy.
Temperature
It handles a wide range, from a cold 0°F (-18°C) up to about 95°F (35°C), which covers winters in zones 6 through 9. The evergreen leaves stay put through the cold and green up again in spring.
Humidity
Ordinary outdoor humidity suits it fine, so there's no number to chase. Drainage matters far more than air moisture, since soggy ground is what causes real harm.
Feeding
Feed lightly in spring, either with a balanced general-purpose fertilizer or by working compost into the soil. This is a low-demand plant, so heavy feeding does little for it.
Pruning
Pruning is barely a chore. Shear off tattered or winter-worn leaves in late winter, just before the new growth pushes up, and the clump comes back fresh.
Repotting
In a container, lift and divide it every 2 to 3 years before the roots crowd the pot. The center of an old clump thinning out or growth slowing down tells you it's time.
Size & spacing
Each clump stays small, reaching 6 to 12 inches (15 to 30 cm) tall with a spread of 8 to 12 inches (20 to 30 cm). Space plants a foot apart for distinct clumps, or closer for quicker groundcover.
When to plant
Black mondo grass is a hardy perennial for zones 6 through 9, so it goes in once and stays. Plant it in spring to give the roots a full season to settle, and look for its small bell-shaped flowers in the warmth of 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 a forgiving plant, and most of its troubles trace back to too much shade or too much water. Read the early signs on the leaves and roots, then act before a small issue spreads. Match what you see below.
Yellowing leaves and a clump that rots in wet soil
Standing wet at the roots brings on root rot, and the foliage yellows and flops once the damage sets in. Dig down and check the roots, since rotted ones turn soft and dark. Work grit or compost into the bed to open up drainage, ease off the watering, and replant healthy divisions somewhere that drains freely.
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 comes back slowly, so fresh divisions can sit quietly for a good while before they push new growth. Divide in spring to hand the plant a full season to settle before winter, and keep the soil evenly moist while new roots form. Give it time instead of digging it 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
This is just the plant's nature. Black mondo grass creeps along on short stolons and takes several seasons to knit together, so a thin look early on is normal rather than a sign of trouble. Set the plants closer, around 4 inches apart, when you want cover sooner, and divide established clumps to fill the gaps.
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 dark color is a sun-driven trait, so plants tucked into deep shade drift back toward green. Move them somewhere brighter and the near-black returns. In hot regions a little afternoon shade is fine, but lean toward sun if color is what you're after.
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
Those holes and slime trails point to slugs and snails, which feed at night and love damp, shady corners. Go out after dark and pick them off by hand. Clear away leaf litter and other hiding spots, and reach for a slug control only where the damage is piling up.
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
Good news for households with pets and children: black mondo grass is not toxic. It belongs to the asparagus family, not the dangerous true lilies it's sometimes mistaken for, and the worst a curious nibbler faces is a mild stomach upset from eating a lot at once.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe to grow around cats. A cat that nibbles a few blades might get a brief upset stomach, the same as with any plant eaten in quantity.
Dogs None
No real danger for dogs. The grass-like leaves hold no known toxin, though wolfing down a big mouthful could leave a dog briefly queasy.
Horses Safe
Not toxic to horses, and it carries none of the poisons found in the true lilies it's sometimes confused with.
Rabbits Safe
Rabbits can graze it without harm. There's nothing poisonous in the foliage, so an occasional bite is fine.
Livestock Safe
Grazing animals are not at risk from this ornamental, which holds none of the compounds that trouble livestock.
Birds Safe
Safe near birds. Backyard poultry can pick at the leaves and small fruit with no cause for worry.
People Safe
Handling and gardening around it pose no risk to people, and a stray taste does no harm 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 few selections and look-alikes turn up under the mondo grass name, and telling them apart comes down to leaf color, flower habit, and fruit. These are the ones worth knowing.
Ophiopogon planiscapus 'Nigrescens'
This is the standard black mondo grass, whose arching grass-like leaves emerge green-purple and mature to a glossy near-black that ranks among the darkest foliage of any perennial.
'Black Dragon' / 'Ebony Knight'
These are trade names sold for the same near-black foliage as 'Nigrescens'.
Ophiopogon japonicus (green mondo grass / dwarf lilyturf)
This is the common green-leaved species, with narrower leaves than Liriope, flowers mostly hidden by the foliage, and blue fruit instead of black.
Black-leaved Liriope (lilyturf)
This belongs to a different genus, Liriope, with broader leaves, flowers held on erect spikes above the foliage, and black fruit rather than 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's really one reliable way to make more black mondo grass, and it keeps the prized dark color true every time.
DivisionEasy
Spring · One growing season
Division is the way to go, since the cultivar won't come true from seed. Split an established clump in spring and the pieces hold their black color and have the whole season to settle in, which takes about one growing season to root and fill out.
Myths
Black mondo grass is a true grass.
Despite the name, it isn't a grass at all. It's Ophiopogon planiscapus, a member of the asparagus family that simply grows in a grass-like, evergreen clump. It only looks the part.
Black mondo grass is the same plant as green mondo grass or lilyturf.
They get mixed up often but they're distinct. Green mondo grass is the related Ophiopogon japonicus, while lilyturf is the separate genus Liriope, which carries broader leaves and flower spikes that stand above the foliage. Black mondo's narrow leaves and hidden flowers set it apart.