Ornamental · Asparagaceae
Black Mondo Grass
Ophiopogon planiscapus 'Nigrescens'
Few plants come this close to true black, and a little sun is what keeps the leaves their darkest.
Full sun
Every 3–7 days
USDA 6–9
6–12 in · 15–30 cm
Overview
Genuine near-black foliage is rare, which is why designers keep reaching for this plant. The arching, grass-like blades start a deep green-purple and darken as they mature, and because it is an evergreen perennial it holds that color through every season. Despite the look, it is not actually a grass; it belongs to the asparagus family (Asparagaceae) and is native to Japan.
As a groundcover it is slow and well-behaved. It spreads on short underground runners, the stolons and rhizomes that widen a clump by inches rather than feet, so it never crowds out its neighbors. That habit makes it easy to place along a path edge, between stepping stones, or massed across the front of a border.
Cold-hardy down to 0°F (-18°C), it asks for little once it has settled in. Give it decent soil, steady moisture, and enough light to keep the leaves dark, and it will hold 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 the old foliage in late winter.
Light
Give it full sun to part shade for the darkest leaves. Deep shade pushes the foliage back toward green because the cultivar needs direct sun to express its darkest pigment. In hot regions, a bit of afternoon shade helps without sacrificing color.
Water
Keep the soil evenly moist, watering roughly every 3 to 7 days during dry spells. It is drought tolerant once established, but steady moisture is what brings out the best color and growth.
Soil
It wants rich, humusy, well-drained loam that is slightly acidic, in the range of 5.5 to 7.0. Work compost in at planting to feed the roots and hold moisture without letting the bed stay soggy.
Temperature
It handles 0°F (-18°C) at the low end and up to about 95°F (35°C), covering zones 6 through 9. The evergreen leaves persist through cold and pick back up in spring.
Humidity
Ordinary outdoor humidity is plenty; there is no target number to chase. Drainage matters far more than air moisture, since soggy ground is what actually does the harm.
Feeding
Feed lightly in spring with a balanced general-purpose fertilizer or compost worked into the soil. This is a low-demand plant, and heavy feeding does little for it.
Pruning
Upkeep is minimal. Shear off tattered or winter-depreciated leaves in late winter before new growth emerges, 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 slowed growth tells you it is time.
Size & spacing
Each clump runs 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 set them closer for quicker groundcover.
When to plant
This is a hardy perennial across zones 6 through 9. Plant in spring so the clump has a full season to establish, and watch for the small, bell-shaped flowers that appear in 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
It 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 and act before a small issue spreads through the clump.
Yellowing leaves and a clump that rots in wet soil
When soil stays saturated, oxygen-starved roots succumb to root rot, and the foliage yellows and collapses once the root system is compromised. Lift the clump and check the roots; rotted tissue is soft and dark. Work grit or compost into the bed to open drainage, cut back on watering, and replant only healthy divisions in a site that sheds water.
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
Because this is a slow-growing species, fresh divisions re-establish gradually and may sit with little visible growth for an extended stretch. Divide in spring so each piece has the whole season to put down roots before winter, keep the soil evenly moist while new roots form, and give the plant time to recover rather than disturbing it 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 species creeps outward on short stolons, so a naturally slow growth rate is the cause rather than a problem to correct. Clumps gain ground by inches over several seasons, and a thin look in the first year or two is simply the plant doing what it does. If quicker coverage matters, set plants closer or divide established clumps to fill the gaps faster.
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 a sun-driven trait, so leaves grown in deep shade revert toward green because the cultivar needs direct light to express its darkest pigment. Moving the planting into brighter conditions restores the dark tone. In hot regions a little afternoon shade is fine, but lean toward sun if color is the priority.
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 paired with slime trails point to slugs and snails, which feed after dark in damp, shaded spots. Pick them off by hand in the evening, clear away leaf litter and other daytime hiding places, and reach for slug controls only when feeding is heavy. Reducing dampness around the clump cuts the pressure.
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
This is not a toxic plant. It sits in the asparagus family, not among the dangerous true lilies it is sometimes mistaken for, and the worst likely outcome is mild gastrointestinal upset from eating a large amount at once. It is safe for households with pets and children.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Carries no toxin for cats; a cat that chews several blades might show brief stomach upset, as any plant eaten in quantity can cause.
Dogs None
No poisonous compound for dogs; a large mouthful at once could leave one briefly queasy and nothing more.
Horses Safe
Safe for horses; it lacks the toxins of the true lilies it is often confused with.
Rabbits Safe
Holds no toxic compound, so rabbits can graze it without harm; an occasional bite is fine.
Livestock Safe
Poses no risk to grazing stock; none of the compounds that trouble grazing animals are present.
Birds Safe
Safe for birds; poultry may pick at the leaves and small fruit without ill effect.
People Safe
No hazard in handling or gardening; a stray taste does no harm beyond the mild upset any non-food plant might bring.
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 show up under the mondo grass name. You can tell them apart by leaf color, flower habit, and fruit.
Ophiopogon planiscapus 'Nigrescens'
The standard black mondo grass; arching grass-like blades emerge green-purple and mature to a glossy near-black, ranking among the darkest foliage of any perennial.
'Black Dragon' / 'Ebony Knight'
Trade names offered for the same near-black foliage you get from 'Nigrescens'.
Ophiopogon japonicus (green mondo grass / dwarf lilyturf)
The familiar green-leaved species; its blades are narrower than Liriope, the flowers stay mostly tucked under the foliage, and it bears blue fruit rather than black.
Black-leaved Liriope (lilyturf)
A separate genus, Liriope, with broader leaves, flowers carried 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 color true every time.
DivisionEasy
Spring · One growing season
Division is the dependable route, since the cultivar will not come true from seed. Split an established clump in spring so each piece keeps the black color and gains the full season to settle; expect about one growing season to root in and fill out.
Myths
Black mondo grass is a true grass.
It is not a grass at all. It is Ophiopogon planiscapus, a member of the asparagus family that simply grows in a grass-like, evergreen clump and resembles one.
It is the same plant as green mondo grass or lilyturf.
These are distinct. Green mondo grass is the related Ophiopogon japonicus, and lilyturf is the separate genus Liriope with broader leaves and flower spikes held above the foliage. Black mondo's narrow leaves and hidden flowers set it apart.