Japanese Forest Grass (Hakonechloa macra)

Forest Grass, Hakonechloa, Hakone Grass, Japanese Forest Grass

Prized for its gracefully arching foliage, Hakone grass, also known as Japanese forest grass, is a tough, low-maintenance ornamental grass that loves moist, shady conditions. This plant forms dense mounds of slender leaves that start solid green, solid golden, or variegated, then change to coppery orange as fall’s cooler weather comes into play. The mounding clumps of grassy leaves gradually slowly increase in size. It is also slow to reappear in the spring so don’t worry if it lags behind other plants in breaking dormancy.

I. Appearance and Characteristics 

Hakonechloa is a genus of bunchgrass in the tribe Molinieae of the grass family, Poaceae, native to eastern Asia.

Hakonechloa macra, with the common names Hakone grass and Japanese forest grass, is the only species in the monotypic genus. It is endemic to Japan.

Hakonechloa macra is a small, mostly shade-loving, clump-forming bunchgrass, slowly spreading in circumference. The stalks cascade in a graceful rounded fountain shape somewhat reminiscent of Pennisetum (fountain grass) but with the actual leaves resembling Chasmanthium. The species tends to be between 45 cm and 60 cm (18″ to 24″) in height.

The leaves are thin and papery and resemble many forms of bamboo. They are very flexible and have a distinctive rustling sound when the wind blows that adds to their appeal. The foliage rises from the roots on thin wiry stalks. The leaf blades are green but many color variations exist. The papery texture keeps the foliage cool to the touch and often the surface is slightly puckered or rippled.

The flowers bloom in midsummer from leaf nodes near the ends of the stalks. The flowers are light purple fading to tan then dropping off over the course of several weeks.

II. How to Grow and Care

Sunlight

Japanese forest grass prefers partial shade, such as that found in woodland areas. In cooler climates, it can tolerate more sun, while in warmer regions it can tolerate near full shade. Part-shade conditions typically produce the brightest yellow in the leaf color; full shade may make the leaves more green than variegated, and full sun can scorch the leaf tips.

Temperature and Humidity

Hakone grass is winter-hardy down to zone 5. Unlike other ornamental grasses, the foliage dies back so it does not provide winter interest. It benefits from a thick layer of mulch to protect the roots.

The grass does well in humid conditions but does not like extreme dry heat.

Watering

This grass requires regular water during the growing season and should not be allowed to dry out. Water it more frequently during hot, dry periods, and keep it protected from hot afternoon sun. Drip irrigation or soaker hoses are great options for applying water in a slow, targeted fashion with minimal evaporation. Containers dry out faster than plants in the ground, and thus potted Japanese forest grass should be watered whenever the top inch of soil feels dry. 

Soil

Japanese forest grass does well when planted in any 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.

Fertilizing

This ornamental grass may benefit from annual fertilizing depending on your soil content. Always test your soil first to determine if it is deficient in any critical nutrients. If nitrogen levels are low, you can apply a well-balanced (10-10-10 NPK), water-soluble formula at half strength in the spring. In addition, consider applying organic mulch around the base of the grass each spring to condition the soil. 

Planting Instructions

Japanese forest grass performs best in partial to full shade and will bleach or burn in overly sunny sites. This grass can tolerate more sun in northern climates if kept consistently moist. It prefers rich, well-drained, moist soil. Dig a hole just wide enough for the root ball, and set the crown slightly above the soil surface to allow the soil to settle over time. Backfill the hole with native soil and water thoroughly to fill in any air gaps around the roots.  Apply a thick layer of compost to keep the root zone cool and conserve moisture.

Pruning

This herbaceous perennial will die back in the winter except in the warmest parts of its growing range. Leave the spent foliage in the winter to protect the crown from freezing temperatures. In the spring, cut back the spent foliage using a pair of sharp, sterilized pruning shears. Trim any sun-burnt leaves during the summer to keep this grass looking tidy. 

Propagation

Division

Named cultivars do not produce viable seeds, so most forms of Japanese forest grass are propagated by division. Here’s how to do it:

  • In spring as active new growth is just beginning, dig up the entire clump, using a shovel.
  • 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.
  • Immediately replant the clumps in well-prepared soil. If using it as a ground cover, plant the pieces 18 to 24 inches apart.

Seed

While named cultivars generally do not produce viable seeds, the pure species form of H. macra can sometimes be propagated by harvesting seeds from the dried flowers and planting them in small containers filled with potting mix. Seeds will take a year or two to develop into viable plants, so it is much more common to propagate by division.

Potting and Repotting 

This ornamental grass can also be grown in containers, where it cascades down over the edge for a nice softening effect. Choose a large pot (any material) that has drainage holes to prevent the soil from becoming boggy, and place the pot in a shady spot that receives some dappled light. Other than that, growing the forest grass in a container is quite easy. Like any potted plant, it will need more frequent watering—daily, in hot conditions. And potted specimens may benefit from a monthly feeding with diluted fertilizer, as frequent watering tends to leach out soil nutrients.

This slow-growing plant will not outgrow its container for many years, if ever. In colder regions, the pots should be moved to a sheltered location (a garage, porch, or cold frame) to go dormant for the winter. Or, the pots can be buried in the garden up to the rim to spend the winter.

Caring in Pots

This grass looks fantastic in containers. Choose a weather-proof container with large drainage holes for plants grown outdoors. The container should be big enough to allow the roots to expand over the next year or two. Use potting soil that retains moisture but drains well to prevent root rot. Cover the roots with soil only to the depth that the grass was originally planted, and leave a couple inches at the top of the container for watering. Water regularly during the summer when the top inch of soil is dry to the touch, approximately 2 times per week.

Overwintering

Japanese forest grass does not need any special winter care. During the winter, the foliage will turn yellow and eventually die back. You can leave the spent foliage for winter protection. At the northern end of its hardiness range, consider adding a thick layer of mulch to protect the roots from winter kill. In the spring, cut this grass back to a few inches above the ground. This is a long-lived perennial that should slowly expand each year.

Pests and Diseases

This plant is nearly immune to serious pest and disease problems, but you may find that winter frost causes the plant crowns to heave up from the ground. Applying a thick layer of mulch over the crowns as winter sets in can help prevent this. If it does occur, it is an easy matter to replant the clumps at the proper depth as new growth begins in spring.

Japanese forest grass can develop scorched, brown leaves if the plant is growing in sunny conditions or in an especially hot climate. This is rarely a serious problem; keep the plant well-watered and prune off dead leaves.

III. Types of Japanese Forest Grass

The pure species form of H. macra has bright green leaves that form a mounding cascade 12 to 18 inches high. A number of good cultivars are also available that offer some variety in leaf color and size:

  • Hakonechloa 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’: With a name translated as “red wind,” this cultivar is green through the summer but takes on varying shades of red as the weather cools off.
  • H. macra ‘Alboaurea’: This cultivar has leaves with long stripes of creamy white, yellow, and bright green.
  • H. macra ‘Naomi’: This yellow and green variegated cultivar turns a striking purplish-red in fall.
  • 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.

IV. Uses and Benefits 

Hakonechloa macra is grown as an ornamental plant, for use in gardens and as a potted plant. The various cultivars of Hakonechloa macra are used as foliage plants in gardens in temperate climates. The species and the cultivars ‘Alboaurea’ and ‘Aureola’ have gained the Royal Horticultural Society’s Award of Garden Merit.

It is mainly used as an ornamental grass in Japanese style gardens, or to brighten shady areas of the garden. The graceful form tends to soften formal shady areas as well. Solid green leaves are the hallmark of the species.

Japanese Forest Grass (Hakonechloa macra) Details

Common name Forest Grass, Hakonechloa, Hakone Grass, Japanese Forest Grass
Botanical name Hakonechloa macra
Plant type Ground Cover
Hardiness zone 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b
Growth rate Slow
Height 1 ft. 0 in. - 1 ft. 6 in.
Width 1 ft. 0 in. - 1 ft. 6 in.
Sunlight Dappled Sunlight (Shade through upper canopy all day)
Soil condition High Organic Matter
Flower color Gold/Yellow
Leaf color Gold/Yellow