Japanese forest grass

Japanese forest grass: how do you recognise it?

Habit

Low, flowing mound 30–40 cm tall and about 50 cm wide, spreading very slowly by short rhizomes.

Leaves

Narrow and lance-shaped, up to about 25 cm long, on thin, arching stems. All the leaves fall the same way.

Colour

Fresh green in the species, golden yellow with green stripes in ‘Aureola’. Orange, red or coppery brown in autumn.

Flowers

Airy, inconspicuous sprays above the foliage in August–September.

Roots

Short, creeping rhizomes. It forms a dense clump but does not run.

Flowering: August–September · Plants: March–May · Pruning: March

Why grow it?

• One of the few ornamental grasses that stays beautiful in partial and full shade.
• Its cascading leaves soften the edges of paths, steps and low walls.
• Interest all season: fresh green or golden yellow in summer, orange to reddish-brown in autumn.
• Not invasive: the clump spreads very slowly.
• Ideal in a pot or tall container, where the leaves spill over the rim.

Japanese forest grass: where does it grow best?

• Partial or light shade is ideal. Golden forms scorch in full sun and turn greener in deep shade.
• Humus-rich loam or peaty soil that does not dry out, acid to neutral. Improve sandy soil first with plenty of compost or leaf mould.
• Normally moist ground: avoid soil that dries out in summer or stays waterlogged in winter.
• Allow 40–50 cm between plants; for a continuous edging, plant 35–40 cm apart.

Light

Partial shade and shade

Soil type

Loam or peat

Acidity

Acid or neutral

Moisture

Normal

Size

0.35 m tall, 0.5 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Hosta: Large, rounded leaves as a calm contrast to the fine, cascading grass.
• Ferns: Together a fresh green shade border full of texture.
• Heuchera: Dark or variegated foliage next to the golden grass.
• Epimedium: An evergreen ground cover for the same partial shade.
• Japanese maple: A classic Japanese pairing, with fine autumn colour.

Japanese forest grass: when and how to plant it?

Plant in March–May.

1. Plant in March, April or May, as the soil warms up, so it has a whole season to root in.
2. Dig a hole twice as wide as the pot and mix in a few spadefuls of compost or leaf mould.
3. Set the clump at the same depth as it was in the pot, no deeper, or the crown may rot.
4. Space plants 40–50 cm apart and turn them so the leaves fall towards the path or the front of the border.
5. Water in well straight away and spread a mulch of leaf mould around the clump.

Care

Water

Keep the soil moist in the first year. After that, water only in long dry spells; water pots regularly.

Feeding

A thin layer of compost or organic fertiliser in April. It needs no more.

Mulching

A layer of leaf mould or compost in spring keeps the soil cool and moist and feeds the plant.

Patience

It grows slowly: it takes two or three years to form a nice full clump. Plant closer for a quicker continuous edge.

Pots

Use potting compost with some garden compost added. Repot or divide every few years, once the pot is full.

Tip: Plant it along a path, at the edge of steps or in a tall pot, so the cascading leaves can spill over the edge. Golden forms colour best with some morning sun and shade in the afternoon.

Japanese forest grass: when to prune it?

Pruning months: March.

When: In March, before the new shoots appear. Leave the coloured foliage standing all winter.

How:

• Cut the whole clump back to 2–5 cm above the ground.
• Use sharp secateurs or shears and remove the old leaves with a rake or by hand.
• Do not cut back in autumn: the dry foliage protects the crown from frost and cold wet.

Caution: Do not leave it too late: once the new shoots are up, it is easy to snip off their tips.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In April–May, as growth gets going: use a sharp spade to take a few pieces from the edge of the clump, each with roots and shoots, and replant them at once. As it grows slowly, take fairly large pieces.

Potting up

Pot small pieces up first in potting compost with some garden compost. Let them grow on for a season in partial shade and plant them out in autumn or the following spring.

Japanese forest grass: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy, to about −25 °C: no protection is needed in a Belgian winter.
• Leave the coloured foliage until March: it protects the crown and looks lovely with frost on it.
• Wet feet in winter do more harm than frost: make sure the soil drains well.
• In a pot: stand it against a wall or wrap the pot in hessian so the root ball does not freeze solid.

Diseases and pests

• Slugs: They eat the young shoots in April–May. Check in the evening and pick them off, or trap them under a board where they hide during the day.
• Brown leaf tips: A sign of too much sun or soil that is too dry. Water, mulch and if need be move it to a shadier spot.
• Green leaves on ‘Aureola’: In deep shade the golden foliage turns greener. Light shade or morning sun gives the best colour.
• Slow growth: Normal for this species. Give it humus-rich, moist soil and compost, and be patient: within a few years it fills its space.

Through the year

• March: Cut old foliage back to 2–5 cm. Spread compost.
• April: Plant or divide. Watch for slugs on the young shoots.
• May: Plant. Apply a mulch.
• June: Water in dry spells, especially pots.
• July: Water in dry spells. The foliage is at its best.
• August: Airy flower sprays appear. Water in dry spells.
• September: Flowering. Autumn colour begins.
• October: Autumn colour, orange to reddish-brown.
• November: Leave the foliage standing as winter protection.
• December: Rest. The dry foliage looks lovely in the frost.

Did you know?

• It is named after Hakone, a mountain region near Mount Fuji, combined with the Greek word chloa, grass.
• Hakonechloa macra is the only species in its genus.
• In Britain, ‘Aureola’ has received the Award of Garden Merit from the Royal Horticultural Society, a mark of a reliable garden plant.