How to Care for Monkey Grass

If they handed out awards for the most shade-tolerant, reliably green and easy-care groundcovers, monkey or mondo grass (Ophiopogon japonicus) might easily sweep all three categories. This sturdy Lily (Liliaceae) family ornamental, perennial in U.S. Department of Agriculture plant hardiness zones 7 through 11, grows in full shade to partial sun, tolerates droughts and prolonged wet spells and seldom requires mowing. Monkey grass resists pests and diseases and handles so many conditions so well, in fact, that curbing its spread can require more effort than caring for it.

Once established, monkey grass is an enthusiastic spreader. To get it off to a good start, work 1 to 2 inches of organic compost into the top 6 to 8 inches of the planting site before setting out the plants. Figure on 30 to 60 pounds of compost for each 10 square feet of soil.

The decaying compost releases a slow, consistent supply of nutrients. In the first three or four years after planting, replenish compost with another 1/2-inch layer spread over the planting bed each spring. After that, fertilizing monkey grass isn't required and may result in its unwanted spread.

Although monkey grass grows from thick roots called rhizomes that hold enough water to carry it through extended dry weather, it performs best in consistently moist, well-draining soil. Like most perennials, it benefits from 1 inch of rain or supplemental water per week during the spring-to-fall growing season.

One inch of rain equals 6 gallons of water for every 10 square feet of soil. To avoid overwatering in rainy weather, use a rain gauge, available at garden supply stores. Check it weekly, and water only when it registers less than 1 inch of rainfall. In a week when the rainfall measures 1/4 inch, for example, water the monkey-grass bed at the rate of 4 1/2 gallons for every 10 square feet.

The best time to water is early in the morning, so the foliage dries as quickly as possible. Soak the soil around the plants slowly and deeply, giving the water time to penetrate to the roots.

Winter often leaves monkey grass tattered and torn. To help it recover, rake up dead leaves and prune the plants back by one-third before their new growth begins emerging in spring. Trim them with sharp, clean hedging shears, wiping the blades down with a rag dipped in rubbing alcohol between cuts so they don't spread disease.

Mowing monkey grass once or twice during its first two or three growing seasons helps it fill large areas more quickly, even though the individual clumps look smaller for a while afterwards. Protect the plants' crowns by adjusting the mower blades to their highest setting.

Disease and pests seldom trouble monkey grass, but yellowing or browning edges or reddish or tan spots on the leaves indicate anthracnose infection. Using sharp pruning shears wiped down with rubbing alcohol between cuts, remove the diseased leaves and dispose of them in sealed plastic bags. To keep spores from splashing on the plants, keep the bed clear of potentially infected debris.

Treat recurring anthracnose as soon as symptoms surface with ready-to-use chlorothalonil fungicide. On a calm, cool dry day with no rain predicted for at least 24 hours, put on protective clothing, chemical-proof gloves, safety goggles and a respiratory mask and spray until the fungicide drips from the plants.

Keep people and pets out of the sprayed area until the plants dry. Repeat every one to two weeks, or as often as the manufacturer advises, while wet weather persists. Always follow the label instructions when using any fungicide.