Ornamental · Poaceae
Japanese Forest Grass
Hakonechloa macra
Give it shade and steady moisture, and this grass spills over the edge of a bed like falling water.
Partial shade
Every 3–7 days
USDA 5–9
12–18 in · 30–46 cm
Overview
Japanese forest grass is the rare ornamental grass that wants shade, not sun. It comes from the wooded mountains of Japan, where it grows on damp, rocky slopes, and it brings that same soft, cascading mound to a shady corner of the garden. The blades arch in one direction, so a row of it looks like green water pouring downhill.
It grows slowly and stays low, reaching only 12 to 18 inches (30 to 46 cm) tall, which makes it easy to place along a path or at the front of a shade bed. The gold and variegated forms, like the well known Aureola, light up dim spots that most plants struggle in. Green types turn fiery shades of red and orange before they fade for winter.
Easy is the word for it once the spot is right. Keep the soil rich and evenly moist, give it shade from the harsh afternoon sun, and it asks for almost nothing else. The main test of patience is its pace, since a young clump takes a few years to settle in and spread.
Care
The short version: partial to dappled shade, soil kept rich and evenly moist, and a yearly cut back in late winter. Give it slightly acidic ground, shelter from hot afternoon sun, and the patience to let a slow clump fill in.
Light
This grass wants partial to dappled shade, which sets it apart from most ornamental grasses. It takes full shade and a bit of morning sun, but hot afternoon light scorches the blades. Gold and variegated forms keep their best color in bright shade, not deep gloom.
Water
Keep the soil consistently moist, since this is a moisture lover that scorches the moment the ground dries out. Heat and sun make it thirstier still. Water deeply through dry spells and mulch to hold that moisture around the roots.
Soil
Plant it in humus-rich, well-drained ground on the slightly acidic side, around a pH of 5.5 to 6.5. Plenty of compost worked in feeds the slow roots and helps the soil stay evenly damp without turning waterlogged.
Temperature
It's tough through cold, hardy down to about -20°F (-29°C), and handles summer warmth up to roughly 84°F (29°C). Heat alone is fine; it's heat paired with dry soil or strong sun that burns the leaves.
Humidity
Ordinary garden humidity suits it, so there's no number to hit. Steady soil moisture matters far more than the air, and that's what keeps the foliage from crisping at the tips.
Feeding
Feed once in spring with a balanced fertilizer, or simply top-dress the crown with compost or organic matter. That single seasonal feed is enough to keep a clump healthy and growing.
Pruning
Cut the old foliage right to the ground in late winter or early spring, before the new shoots push up. The plant dies back fully and gives nothing over winter, so the only real pruning is that one clean cut each year.
Repotting
Lift and divide a clump every 2 to 3 years, or when the center grows congested and starts to die out. Reduced vigor and roots heaving the crown are the other signs it's time to split and replant.
Size & spacing
Plants reach 12 to 18 inches (30 to 46 cm) tall and spread 18 to 24 inches (46 to 61 cm) wide. Give each clump that much room and let the slow grower fill the gap on its own over a few seasons.
When to plant
There's no harvest to chase with this grass, just a steady rhythm to follow. Plant it out in spring, cut the old foliage to the ground in late winter before the new shoots come up, and watch for its quiet yellow-green flower spikes in late summer.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring
- Harvest: late summer (July to August), inconspicuous yellow-green flower spikes
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Most trouble with Japanese forest grass comes down to the wrong amount of light or soil that runs too dry. Read the leaves and they'll tell you which it is. Match what you see below, then adjust the spot or the watering before the look of the clump suffers.
Clumps that barely spread from one year to the next
This is just slow growth, the normal pace for this grass, which establishes over several seasons rather than racing to fill a bed. Dry or poor soil slows it down even more. Be patient, keep the ground rich and evenly moist, top-dress with compost in spring, and mulch the crowns over winter so frost can't heave them.
Fix:
- Be patient; it is a slow grower that establishes over several years
- Maintain rich, evenly moist soil and a spring top-dress of compost
- Mulch crowns over winter to prevent frost heaving
Scorched, crisped leaf tips and bleached blades
This is sun scorch, and it shows up when the grass takes too much hot, direct sun or the soil dries out in the heat. Gold and variegated forms burn the worst, especially under harsh afternoon light. Move the clump into part to dappled shade, keep the soil steadily moist, and mulch to hold that moisture in.
Fix:
- Move or site in partial to dappled shade, giving only morning sun in hot climates
- Keep soil consistently moist and mulch to conserve moisture
- Water deeply during heat and drought
Gold color washing out to plain lime green
Too much shade is draining the color from gold and variegated forms, leaving them dull and flopping open instead of mounding tidily. The fix is more light, not less. Shift colored cultivars to bright dappled shade or a spot with morning sun, where the gold deepens and the clump holds its shape. Save the deep shade for green forms that don't depend on bright leaves.
Fix:
- Move gold and variegated forms to brighter dappled shade or morning sun for best color
- Accept that color is most vivid in part shade, not deep shade
Ragged holes chewed through the blades
Slugs are the likely culprit, turning up now and then in the damp, shady spots this grass loves. Look for irregular holes and slime trails, worse after wet weather. Hand-pick the slugs or set out controls, clear away debris where they hide, and open up the clumps for better airflow. Beyond the odd slug, the species has no serious pests.
Fix:
- Hand-pick slugs or use slug controls
- Reduce excess debris and improve air circulation around clumps
Toxicity
Good news for households with pets and children. Japanese forest grass is not toxic and doesn't appear on the ASPCA's poison lists, so a nibble of the blades won't harm anyone. The worst that might happen is a little mild vomiting, the same as with any grass, or some sneezing from grass pollen in people prone to allergies.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe to be around. A cat that nibbles the blades might bring up a little, the same as with any grass, but nothing in the plant is poisonous.
Dogs None
No toxins here, so a curious dog is fine. The most you'll see from a mouthful of leaves is the odd bout of mild vomiting, just as grass tends to do.
Horses None
This is an ordinary, non-toxic grass and poses no danger to grazing horses.
Rabbits None
Rabbits can be around it without worry; the foliage holds nothing harmful if they nibble.
Livestock None
Cattle, goats, and sheep face no risk from this grass, which carries no toxic compounds.
Birds None
Harmless to birds, whether they perch in it or peck at the seed heads.
People None
Safe around children and adults alike. The only catch is grass pollen, which can stir up allergies in people already sensitive to it.
Not poisonous, but pets that nibble grass foliage may occasionally vomit, and grass pollen can trigger allergies in sensitive individuals.
Varieties
A handful of cultivars carry this grass, sorted mostly by leaf color and how brightly they glow in shade. These are the ones worth knowing.
Aureola
Gold leaves striped with narrow green, this 2009 Perennial Plant of the Year holds its best color in part shade.
All Gold
Solid bright golden-yellow blades stand more upright and spiky than the arching Aureola.
Beni Kaze
Its green blades, whose name means red wind, turn red and gold once fall arrives.
Nicolas
A compact green selection that lights up with fiery orange and red in autumn.
How to propagate
You make more Japanese forest grass by splitting an established clump, a slow but dependable job best done in spring.
DivisionEasy
Spring, just as new foliage emerges · Slow; clumps need 2 to 3 years between divisions and are slow to fill in
Division is the easiest way to make more, and the surest way to keep a cultivar's color true. Split the clumps in spring as the new foliage emerges. Work slowly, since these grasses take 2 to 3 years to fill back in between divisions. The species can also come up from seed, but seedlings won't hold the parent's coloring.
Myths
All ornamental grasses need full sun.
Japanese forest grass is one of the few grasses that actually prefers shade, and a standout for shady beds. Hot, full sun scorches it, while partial to dappled shade brings out its best color and that graceful, cascading shape.