A popular ornamental plant, black mondo grass adds year-round interest to gardens. It produces delicate flowers in the summer and berries in the fall, but it’s the dark-colored foliage that makes the plant stand out. The foliage also changes color according to the amount of light it receives. If grown in full shade, the leaves turn a lighter color.
I. Appearance and Characteristics
Ophiopogon planiscapus is a species of flowering plant in the family Asparagaceae. It is native to Japan, where it grows on open and forested slopes.
The long, slender and strap-like leaves of black mondo grass can range from green to purplish-black. The warmer the weather, the darker their coloring becomes. That deep coloration can provide a dramatic counterpoint to brighter blossoms.
Not all forms of mondo plant are black! There are cultivars that are much lighter in color. While they also darken in the sun’s warmth, their edges can stay off-white. The centers of the leaves remain a dark green hue. Lighter plants are often called lilyturf, a name often used for Liriope species as well.
Forming tight, matted clumps in its bed, the black mondo grass perennial grows in zones 6-10. It provides year-round color in those zones, but its active growing season occurs in spring and summer. Called monkey grass in the southern US, this plant also produces flowers on a long, slender raceme in fall.
II. How to Grow and Care
Light & Temperature
Full sun to partial shade is what’s recommended for black mondo grass, but it should be a “cool full sun” condition. If you’re in a hot, desert-like climate, afternoon shade is preferable. Too much full sun or direct sunlight in extreme heat can damage the tender leaves.
Black mondo grass is considered “cold-hardy”, but that should actually mean “frost-tolerant”. If you get hard freezes, your plant will suffer. The rare light frost shouldn’t do more than cosmetic damage.
Water & Humidity
While Ophiopogons have relatively mild water requirements, they still need moisture. With these, maintaining a consistently-damp soil is going to help keep them healthy. Consistent watering also improves flowering capability. However, they do not like overly wet conditions.
During the first year after planting, water black mondo grass a bit more regularly. After it’s established, it can tolerate the occasional dry period. But it does still prefer even moisture levels.
A mulch can help maintain the moisture of the soil around black mondo grass. Those in direct sunlight will thank you. Opt for something which sets off the look of the grass-like leaves well, like a contrasting wood chip.
Black mondo grass is tolerant of humidity as long as there’s good airflow around its location. If it’s boxed in and the air is hot and sticky, it may wilt a bit.
Soil
Humus-rich, slightly-acidic well-draining soil is best for your black mondo grass. Aim for a pH range between 5.5 and 6.5 for best growth. Avoid clay-like soils when possible, as these are too hard for the roots to penetrate easily.
Excess water needs to drain away to prevent root damage. Avoid muddy conditions, especially in hot climates!
Fertilizing
Fertilizing black mondo grass with a balanced fertilizer should be rare. A spring application of compost around the plant’s base should be more than enough to feed it and support the plant’s health.
Pruning
Some sources have suggested mowing your black mondo grass. Please don’t do that. It can take months to years to recover.
This plant seldom, if ever, needs pruning. Instead, remove dead or disfigured leaves as necessary. Pruning is wholly cosmetic.
Propagation
While black mondo grass will spread, its spread is very slow. It’s much easier to divide off new plants in the spring.
Remove a large clump of black mondo grass from the soil, being careful to not harm its fibrous root system. Dust off excess soil. Using your hands, separate off smaller clumps, each with its own roots and leaves.
Once separated, you can plant black mondo grass at 4″ intervals to provide a good cover. Carry out mass planting of large quantities of plugs and you’ll have an entire garden of the stuff.
You can grow black mondo grass from seed contained within its purple berries, but it is time-intensive. Black mondo seed has a low germination rate. It’s also slow to germinate and can take anywhere from 30-150 days. Since it’s a slow-growing plant, preparing enough starts for a ground cover takes a while!
Pests and Diseases
- Common Pests
Most pests seem to ignore black mondo grass!
But there are two that don’t, both related: snails and slugs. These can chew holes in leaves or gnaw the leaves right off your gorgeous black mondo grass. An application of an organic snail bait like Garden Safe Slug & Snail Bait is a good choice. This bait lures them away from plants and kills them off.
- Common Problems
The biggest problem you’re likely to face – especially in mass planting areas – is pythium root rots. This fungal rot can develop when the soil is too moist, causing yellowing and browning of the plant’s leaves. If not treated, it can lead to black mondo grass plant death.
Treatment of root rot should begin by reducing your watering regimen. Apply a biological fungicide like Serenade Garden Disease Control per the manufacturer’s recommendation. Bacillus subtilis, the active ingredient in Serenade, helps control and prevent pythium.
Underwatering can cause black mondo grass plant wilting. Plants in direct sunlight are more susceptible. If the soil is dry more than an inch below the surface, it’s time to water. Consider adding mulch to slow the evaporation of soil moisture, especially in zones with extreme heat.
Avoid excessive pruning, as the plant grows quite slowly. Too much pruning will make it look less appealing.
III. Types Of Mondo Grass
- Ophiopogon planiscapus ‘Nigrescens’
This is the deepest and the darkest variety, the one which gave mondo grass its “black” name. Reported to have a sweet fragrance, it blooms with lavender to purple bell-shaped flowers. In time, these flowers produce an inedible berry that holds its seeds.
The long leaves of this black mondo grass begin as dark green but deepen in the heat to become so dark they turn charcoal-colored. Slightly reflective, they can have a greyish cast to them in certain lighting. These can survive in USDA zones 5-10 but do especially well in zones 7-9.
- Ophiopogon planiscapus ‘Little Tabby’ or ‘Silver Ribbon’
A pair of popular cultivars, Little Tabby and Silver Ribbon, are both similar in color. These are more commonly called lilyturf or monkey grass than mondo grass. Silvery-white edges fade into a vivid, dark green leaf.
The flowers for these are white but also morph into a deep purple-colored inedible berry as they fade. These are sometimes confused with Ophiopogon intermedius, called Aztec grass. But Aztec grass grows to 12-24″ in height, where these stay closer to the ground.
IV. Uses and Benefits
- Garden uses
The cultivar ‘Kokuryu’ (black mondo) is grown as ground cover, or as underplanting for larger shrubs. Its leaves turn from green to dark purple (black) and can grow to 8 in (20 cm) tall and 1⁄4 in (0.64 cm) wide. The pale lilac flowers are followed by black berries. It is also known as ‘Black Dragon’, ‘Nigra’ or ‘Nigrescens’. It has received the Royal Horticultural Society’s Award of Garden Merit.
There are also two variegated forms called ‘Little Tabby’ and ‘Silver Ribbon’. These are green with white borders around the leaves.
