Learn How to Grow Black Mondo Grass

Ophiopogon planiscapus

A unique ornamental, black mondo grass (Ophiopogon planiscapus) is highly valued for its versatility in the landscape, forming lush, arching mounds of black, bladed foliage.

An evergreen perennial that grows from stolons, the tufts of strappy, grass-like leaves are perfect for adding a dash of drama or polished finish to mixed borders, edging, and containers.

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It can also be used in mass plantings, as ground cover, and throughout rock gardens.

Low maintenance and drought resistant once established, deer and rabbits prefer greener pastures and tend to leave black mondo grass alone!

Easy, attractive, and polished: are there spots in your garden that need a splash of dark drama? Then let’s shine a light on how to grow and care for black mondo grass!

Here’s what you’ll find ahead:

Sometimes called black lily-turf, black mondo grass is native to Japan, a mounding, grass-like perennial with running roots, or stolons, in the asparagus family, Asparagaceae.

A stemless plant, the narrow, basal leaves grow in attractive arching clumps that spread slowly to a size of eight to 15 inches tall and up to 12 inches wide.

The lustrous leaves are typically dark green at the base and quickly transition to nearly black or deep, dark aubergine all the way to the tips.

In early to midsummer, flower scapes rise through the foliage and produce pretty racemes of lightly fragrant mauve, pale pink, or white bell-shaped flowers.

By fall, the scapes are adorned with small, round berries of black or deep purple, which often persist through winter.

To learn about the equally attractive green-hued Ophiopogon varieties, head over to our guide on how to grow and care for mondo grass.

Valued for the dense mounds of graceful foliage, a light spring cleanup is typically all that’s needed to maintain attractive, vibrant plants.

Their easy nature thrives in full sun to dappled shade, and they flourish in most settings, including beds, borders, containers, edging, ground covers, underplanting trees and shrubs, and window boxes.

The dark color makes a striking contrast when mixed with other low-growing perennials like crocus, cyclamen, creeping phlox, and snowdrops, and the plants make a superb addition to gravel, meditation, or rock gardens.

How to Grow

Plant in spring to ensure roots are well established before winter arrives.

Before planting, loosen the soil to a depth of 12 inches and enrich by mixing in compost, leafmold, well-rotted manure, or worm castings – use one shovelful for each plant.

To help establish strong, healthy roots, mix in a tablespoon of bone meal or a tablespoon of a balanced, slow-release fertilizer with a formula such as 5-5-5 (NPK).

Space plants 10 inches apart, placing the crown just below soil level. Backfill with soil, gently firming it in place over the rootball.

Water lightly to settle in place.

Climate

Adaptable to a range of conditions in Zones 6 to 10, black mondo grass thrives in a variety of humidity levels provided the soil is kept lightly moist.

It’s also salt tolerant and makes a good choice for coastal gardens.

However, plants struggle in hot conditions if temperatures rise above 85°F.

Light

Black mondo grows in full sun to part shade, but the darkest hues develop in full sun.

In areas with hot, intense sunshine, some afternoon shade is beneficial to protect the leaves from scorching.

Soil

These plants do best in moderately fertile, well-draining soil with a slightly acidic to neutral pH of 5.5 to 7.0.

To sharpen the soil and improve drainage, mix in one shovelful of grit using materials like landscape sand, pea gravel, crushed shells, or stone chips.

To acidify the soil, the addition of garden sulfur is an economical, long-lasting solution.

But sulfur needs to be added in advance – the fall before a spring planting is best. First, test your soil with a pH probe to determine how much sulfur you need.

DTE Garden Sulfur Soil Acidifier

Then add in a product like DTE Garden Sulfur Soil Acidifier, available at Arbico Organics, it’s ideal for promoting bluer hydrangeas too.

Water

Once established, black mondo grass has good drought resistance but plants do best in lightly moist conditions.

Provide one or two inches of water per week, applying when the topsoil is dry to a depth of one to two inches. Soak deeply to ensure the entire root ball is watered.

Container plants, especially those in full sun, need more frequent water applications in summer. Check regularly to keep the soil on the lightly moist side.

Fertilizer

Although black mondo grasses aren’t heavy feeders, a spring feeding is beneficial for healthy growth.

In early spring, spread one or two inches of compost, leafmold, manure, or worm castings over the root zone.

Gently lift the foliage to spread the fertilizer close to the crown, but don’t crowd the base of the plant.

An alternative to compost is slow-release fertilizer granules. Gently scratch them into the soil surface over the root zone with a hand cultivar or garden knife like a hori hori.

Use a balanced, slow-release fertilizer with equal amounts of nitrogen, phosphorus, and potassium or an all-purpose formula with slightly higher nitrogen levels.

Burpee Enhanced Fertilizer

Burpee’s Enhanced Fertilizer, available from Burpee, is a good choice for a balanced formula with a 5-5-5 NPK.

Arber All-Purpose Fertilizer

I also like Arber All-Purpose Fertilizer with a NPK of 3-2-1, which is available at Arbico Organics.

Both of these products are certified organic.

Where to Buy

The most popular dark-colored cultivar of O. planiscapus is ‘Kokuryu,’ which goes by several synonyms including ‘Arabicus,’ ‘Black Dragon,’ ‘Ebony Knight,’ and ‘Nigrescens.’

‘Black Beard’ is another dark-hued variety and very similar to ‘Kokuryu.’

Black Mondo Grass

You can purchase plants in one-gallon pots at Fast Growing Trees.

Or if you prefer something smaller, starter plants of ‘Kokuryu’ in four-inch pots are available at Burpee.

Maintenance

Easy-care mondo grass requires only a light cleanup in early spring to maintain an attractive and healthy form.

Before new growth ramps up in spring, use clean, sharp garden scissors to snip off dry, dead, or brown blades, cutting close to the base.

Container grown plants, and mature black mondos in restricted spaces like beds or borders, require division every three to five years – we cover how to divide below, so keep reading!

Propagation

Division of stolon offsets is the easiest and quickest way to propagate established plants and is best done in early spring when new growth starts to emerge.

Here’s how:

1. Water plants a few hours before dividing – having the soil lightly moist makes it much easier to pry the dense roots apart.
2. With a small spade, dig into the soil to a depth of about eight inches and lift each root ball. The roots are mostly shallow with the majority of spreading stolons clustered close to the surface.
3. Use your fingers to pry apart offsets or small clusters of offsets from the rootball. Start at the outer edges and work to the center.
4. Overgrown roots can be very tightly packed and difficult to untangle, but these are tough little plants and can handle some rough treatment. Use the tip of a garden knife as a lever if needed.

Replant one of your divisions in the original location and transplant the remainder as desired.

Pests and Disease

Black mondo grass has few problems, but there are a couple of issues to watch for.

Root rot can occur if the roots sit in oversaturated soil. Ensure a well-draining location for healthy roots and vibrant plants.

And slugs and snails can nibble on new foliage in moist climates. Our guide on how to protect your garden from snails and slugs has many options for dealing with them.

Darkly Dramatic

With a lush, mounding form, black mondo grass is ideal for adding a dash of darkly dramatic foliage to both sun and shade gardens!

And to sweeten their appeal, summer brings pretty racemes of small flowers followed by dark berries in fall and winter.

Wonderfully low maintenance, mature plants need only a spring cleanup, an early dose of compost or slow-release fertilizer, and regular watering to thrive in settings from beds and borders to containers or ground covers.

Do you grow your black mondo grass in sun or shade? Or both? Let us know in the comments section below!

And for more ideas on hardworking grasses and grass-like plants, add these guides to your reading list next:

• Learn How to Grow Zebra Grass
• How to Grow Ornamental Maiden Grass (Japanese Silver Grass)
• How to Plant, Grow, and Care for Purple Fountain Grass