A ground cover plant that forms neat clumps of dark green, grasslike leaves, dwarf mondo grass (Ophiopogon japonicus "Nanus") grows best in evenly moist soil and filtered sun, such as dappled shade from a tree. A mature plant is 4 inches tall and spreads 6 inches wide, and in summer bell-shaped, white or pale lilac flowers appear, adding 2 inches to the plant's height. Dwarf mondo grass grows in U.S. Department of Agriculture plant hardiness zones 6 through 11.
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Where to Plant
Sandy loam soil is best for dwarf mondo grass, but it tolerates a range of soil types and growing conditions. A high or low soil pH doesn't bother this plant, and it tolerates urban pollution. Though it grows best in moist soil, it tolerates drought, but poorly drained soil and standing water cause problems. Dwarf mondo grass is salt-tolerant and grows well in a coastal garden.
To create a carpet of ground cover, space dwarf mondo grass so the center of one plant is 6 inches from the center of the next. You can also evenly space the plants further apart, and spread mulch between them, for a formal effect.
Water and Fertilizer
Dwarf mondo grass needs careful watering during its first season, but rarely needs fertilizer. Water newly planted dwarf mondo grass when the soil surface is dry, to help establish a deep root system. Apply water until it begins to puddle on the soil surface. In following years, water established dwarf mondo grass when the soil is dry to a depth of 3 inches.
Dwarf mondo grass doesn't need fertilizer if it's growing strongly and has lush, deep green leaves. If the plant is growing poorly and has pale leaves, and there's no other possible cause, it may be suffering from nutrient deficiency. Fertilize nutrient-deficient dwarf mondo grass with a 12-4-8, slow-release, granular fertilizer. Sprinkle the granules at a rate of 4 tablespoons per 4 square feet around the plant base, avoiding the leaves. Use a hose over the area to water the fertilizer in and knock any off the leaves.
Dwarf mondo grass needs tidying up only once a year, in spring. Remove faded foliage from the previous year to neaten up the plant and make room for fresh, new growth.
Sterilize pruning shear blades by wiping them with a cloth soaked in rubbing alcohol, and tidy dwarf mondo grass in early spring, before new growth appears. Prune all the stems to 1 inch tall, and remove the clippings from the area. Sterilize the pruning shears again when you've finished.
Dividing Dwarf Mondo Grass
Dividing dwarf mondo grass helps maintain healthy growth. When the plant is 2 or 3 years old, dig it up and divide it into sections in early spring.
Before new growth appears, dig up dwarf mondo grass with a garden fork. Pull the root ball into two or three sections with equal amounts of top growth. You can cut the root ball with a knife sterilized with rubbing alcohol, if necessary. Plant each section at its original growing depth, and space the sections 6 inches apart. Water each newly planted section until the water begins to puddle. Dwarf mondo grass lives about 10 years in good growing conditions.