How to Grow and Care for Japanese Forest Grass

Japanese Forest Grass Care

This ornamental grass requires little maintenance. Here are the main care requirements for growing Japanese forest grass:

• Plant it in a location with partial shade and moist, well-drained soil rich in organic matter.
• Water it regularly in the absence of rain to keep the soil evenly moist.
• Spread mulch over the ground around the plant to keep the soil cool, retain moisture during summer, and protect it from the cold in the winter.
• Fertilize it once in the spring with a complete balanced fertilizer (optional).

Light

Japanese forest grass prefers partial shade, such as that found in woodland areas. In cooler climates, it tolerates more sun, while in warmer regions it tolerates almost full shade.

Soil

The grass thrives in moist, well-drained soil with a good amount of humus and other organic matter. Dense soils should be amended with compost or peat moss before planting. Sightly acidic soil with a pH around 6.0 is best.

Water

Moist soil at all times is key; if there is not sufficient rainfall, Japanese forest grass needs frequent watering of 1 inch per week, divided into two or three equal waterings. A good amount of water-retentive organic matter in the soil helps to retain moisture.

Temperature and Humidity

The climate in the native habitat of the grass is cool and moist but if you give it shade, water it regularly, and keep its roots cool by mulching, it potentially does well in warmer areas as well. It does not tolerate extreme heat or cold. The grass is reliably hardy up to USDA Zone 5, but with a thick layer of mulch, it can survive the winter in USDA Zone 4.

Fertilizer

Organic mulch provides all the nutrition this plant needs. At the most, fertilize the grass once in the spring spring just after the first new growth appears, using a compete balanced fertilizer.

Types of Japanese Forest Grass

In addition to the pure species form of Hakonechloa with bright green leaves, there are several cultivars offering variety in leaf color and size:

• H. macra ‘Aureola’: This beautiful variegated form has chartreuse and green leaves that form an elegant mounding cascade 12 to 18 inches tall.
• H. macra ‘Albostriata’: The green leaves on this cultivar have thick and thin creamy white stripes. The plant is more sun-tolerant than the golden forms, and it grows faster and taller, to as much as 36 inches. It may also be more cold-hardy than the other cultivars.
• H. macra ‘All Gold’: This cultivar has brighter leaves and is comparatively upright and spiky in form. The overall plant is smaller and grows slower than the other cultivars.
• H. macra ‘Benikaze’: Green through the summer, the leaves of this cultivar take on varying shades of red as the weather cools off.
• H. macra ‘Alboaurea’: The leaves of this cultivar have long stripes in creamy white, yellow, and bright green.
• H. macra ‘Naomi’: In the fall, the leaves of this yellow-and-green variegated cultivar turn a striking purplish-red.
• H. macra ‘Nicolas’: This unusual cultivar has brilliant green foliage that turns striking shades of red, yellow, and orange in fall before dying back for winter.

Pruning

No pruning is necessary other than removing dead leaves. At the end of the growing season, cut the dead foliage back to the ground level before mulching for the winter, except at the low end of the zone range where it is better to leave the foliage in place until spring, which helps to insulate the crown.

Propagating Japanese Forest Grass

All types of Japanese forest grass are best propagated by division. as cultivars do not produce viable seeds and seeds from the species take a year or two to develop into viable plants. Here’s how to divide the plant:

1. In spring, as active new growth is just beginning, dig up the entire clump with a shovel.
2. Use a spade or garden knife to divide the clump into three or four sections, each with a healthy group of roots and some active shoots.
3. Immediately replant the clumps in well-prepared soil. If using it as a ground cover, plant the sections 18 to 24 inches apart.

Potting and Repotting Japanese Forest Grass

Japanese forest grass is also handsome in containers, where it cascades down over the edge for a nice softening effect. Choose a large pot (any material) that has large drainage holes and fill it with rich, well-draining potting soil.

Place the pot in a shady spot that receives some dappled light. It will need more frequent watering up to daily, in hot conditions. Potted specimens may benefit from a monthly feeding with diluted fertilizer, as frequent watering tends to leach out soil nutrients.

This slow-growing grass will not outgrow its container for many years, if ever. Repotting it every few years is still recommended to refresh the soil.

Overwintering

To protect the crown against the freezing cold and damaging freeze-thaw cycles, apply a thick layer of mulch over the crown in the fall.

Common Pests & Plant Diseases 

There are virtually no serious pest or disease issues with Japanese forest grass.

Common Problems With Japanese Forest Grass

Frost Heave

Winter frost causes may cause the plant crowns to heave up from the ground. To prevent this from happening, apply a thick layer of mulch over the crowns as winter starts. If frost heave occurs, replant the clumps promptly at the proper depth as new growth begins in spring.

Scorched Leaves

Too much sun causes scorched, brown leaves or leaf tips, especially in a hot climate. Make sure to select a planting location in partial shade and if necessary, move the grass to a suitable location with less sun exposure.