Ornamental · Poaceae
Japanese Forest Grass
Hakonechloa macra
Give it shade and steady moisture, and this forgiving grass spills over a bed's edge like softly falling water.
Partial shade
Every 3–7 days
USDA 5–9
12–18 in · 30–46 cm
Overview
If most grasses have scared you off with their hunger for full sun, this one is on your side, because Japanese forest grass wants shade instead. It hails from the wooded mountains of Japan, growing on damp, rocky slopes, and it brings that same soft, cascading mound to a shady corner you may have struggled to fill. The blades all lean one way, so a run of it looks like green water pouring gently downhill.
You'll find it stays low and grows at a calm pace, topping out at just 12 to 18 inches (30 to 46 cm), which makes it forgiving to place along a path or at the front of a shade bed. The gold and variegated forms, like the much loved Aureola, brighten dim spots where other plants sulk. Green types reward you with fiery reds and oranges before they rest for winter.
Once you get the spot right, this really is an easy plant to keep happy. Keep the soil rich and evenly moist, shelter it from the harsh afternoon sun, and it asks almost nothing more of you. The only patience it tests is its speed, since a young clump takes a few seasons to settle and spread, and that is completely normal.
Care
The short version: partial to dappled shade, soil kept rich and evenly moist, and one gentle cut back in late winter is all it asks. Give it slightly acidic ground, shelter from hot afternoon sun, and a little patience while a slow clump finds its feet.
Light
This grass is happy in partial to dappled shade, which sets it gently apart from most ornamental grasses. It'll take full shade and a little morning sun, but hot afternoon light scorches the blades, so spare it that. 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 only make it thirstier. Water deeply through dry spells and lay down mulch to hold that moisture around the roots, and it will thank you.
Soil
Give it 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 ever turning soggy.
Temperature
It's wonderfully tough in the cold, hardy down to about -20°F (-29°C), and it takes summer warmth up to roughly 84°F (29°C) in stride. Heat on its own is fine; it's heat paired with dry soil or strong sun that burns the leaves.
Humidity
Ordinary garden humidity suits it beautifully, so there's no number you need to chase. Steady soil moisture matters far more than the air, and that's what keeps the tips of the foliage from crisping.
Feeding
Feed it just once in spring with a balanced fertilizer, or simply top-dress the crown with compost or organic matter. That single seasonal feed is plenty to keep a clump healthy and quietly growing.
Pruning
Cut the old foliage right to the ground in late winter or early spring, before the new shoots push through. It dies back fully and gives nothing over winter, so that one clean cut a year really is the only pruning you'll do.
Repotting
Lift and divide a clump every 2 to 3 years, or when the center gets congested and begins to die out. Reduced vigor and roots heaving the crown are the other quiet signs that 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 simply let the slow grower fill the gap on its own over a few seasons.
When to plant
There's no harvest to worry about with this grass, just a gentle rhythm to keep. Set it out in spring, cut the old foliage to the ground in late winter before the new shoots appear, and enjoy 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
Almost every hiccup with Japanese forest grass traces back to the wrong amount of light or soil that has gone too dry, and the plant will tell you which. Read the leaves, match what you see below, and a small tweak to the spot or the watering usually sets it right before the clump looks any worse.
A young clump that barely widens each year
Take heart, this is nothing more than slow growth, the honest pace of this grass, which settles in over several seasons instead of rushing to fill a bed. Dry or thin soil holds it back further still. Give it time and it will get there: keep the ground rich and evenly moist, top-dress with compost in spring, and tuck mulch over the crowns through winter so frost can't lift 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 leaf tips and pale, crisped blades
Don't worry, those crisped edges are simply sun scorch, and they turn up when the grass gets too much hot, direct sun or the soil goes dry in the heat. Gold and variegated forms feel the harsh afternoon light most, so they burn first. You can turn this around: slide the clump into part to dappled shade, keep the soil steadily moist, and lay down mulch to lock 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 fading toward flat lime green
When too much shade drains the color from gold and variegated forms, they turn dull and flop open rather than mounding neatly, and the good news is the cure is more light, not less. Ease colored cultivars into bright dappled shade or a corner with morning sun, and the gold warms back up while the clump holds its rounded shape. Let the deep shade go to the green forms, which don't lean on bright leaves at all.
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 nibbled through the blades
The likely visitors are slugs, which wander into the damp, shady spots this grass is so happy in. Watch for irregular holes and shiny slime trails, worse after a wet stretch. You can handle it easily: pick the slugs off by hand or set out a control, sweep away the debris where they hide, and loosen the clumps so air moves through. Apart from the odd slug, this grass gives you no serious pests to fret over.
Fix:
- Hand-pick slugs or use slug controls
- Reduce excess debris and improve air circulation around clumps
Toxicity
Here's some reassuring news for homes with pets and children. Japanese forest grass is not toxic and never turns up on the ASPCA's poison lists, so a nibble of the blades won't harm a soul. At worst you might see a little mild vomiting, the same as with any grass, or a few sneezes from grass pollen in someone prone to allergies.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can relax around your cat. If one chews a few blades it might bring a little back up, just as any grass can cause, but nothing in this plant is poisonous.
Dogs None
There's nothing toxic here, so a curious dog is perfectly fine. The most a mouthful of leaves might bring is a touch of mild vomiting, the ordinary grass reaction.
Horses None
Rest easy with grazing horses nearby; this is a plain, non-toxic grass that poses them no danger at all.
Rabbits None
Rabbits are welcome to it without any worry, since the foliage holds nothing harmful should they nibble.
Livestock None
Cattle, goats, and sheep are safe around this grass, which carries no toxic compounds to trouble them.
Birds None
Birds come to no harm here, whether they settle in the blades or peck at the seed heads.
People None
Children and adults are safe around it. The one small thing to note is grass pollen, which can stir allergies in anyone 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 small, welcoming group of cultivars carries this grass, told apart mostly by leaf color and how brightly they glow in the shade. These are the ones worth getting to know.
Aureola
This 2009 Perennial Plant of the Year wears gold leaves striped with narrow green, and it holds that color best when you give it part shade.
All Gold
Its solid bright golden-yellow blades stand more upright and spiky than the gently arching Aureola.
Beni Kaze
Named red wind, its green blades warm to red and gold once fall arrives.
Nicolas
A compact green selection that lights up with fiery orange and red as autumn comes on.
How to propagate
You make more Japanese forest grass by splitting an established clump, a slow but dependable task that's easier than it sounds and 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
Making more of this grass is easier than you might fear, and dividing a clump is also the surest way to keep a cultivar's color true. Split the clumps in spring as the new foliage emerges, and take your time with it. These grasses need 2 to 3 years to fill back in between divisions, so patience is part of the job. You can raise it from seed too, though seedlings won't carry the parent's coloring.
Myths
All ornamental grasses need full sun.
Take comfort here, because Japanese forest grass is one of the few grasses that truly prefers shade, and it shines in a shady bed where little else will. Hot, full sun scorches it, while partial to dappled shade coaxes out its finest color and that soft, cascading shape.