Japanese forest grass

Sun

Partial shade is best. It tolerates deeper shade, but growth may be sparse; morning sun is suitable in cool climates if the soil stays moist. Avoid strong afternoon sun in hot regions.

Water

Keep the root zone evenly moist, especially during establishment and in containers. Water deeply during dry spells; prolonged drought causes browning and early dormancy.

Soil

Humus-rich, moisture-retentive but well-drained soil. Tolerates a range of soil pH levels; avoid waterlogged ground and dry soil crowded with tree roots.

Height

1-2 ft (0.3-0.6 m)

Spread

1-3 ft (0.3-0.9 m)

Flowers

Small, airy greenish flower sprays in late summer, sometimes tinged purple; not a main ornamental feature.

Foliage

Narrow, arching green leaves arranged along slender stems give a layered, bamboo-like appearance. The species is green; named cultivars may be gold or variegated. Leaves often develop bronze or russet tones in autumn before dying back.

Growth

Slow to moderate; allow several years for a substantial clump.

Care needed

Low

• Water when the surface soil begins to dry, keeping the root zone moist without leaving it saturated.
• Apply a thin layer of compost in spring; avoid heavy nitrogen feeding.
• Mulch with leaf mould or fine bark to conserve moisture, keeping mulch clear of the crown.
• Divide established clumps in spring only when you need more plants or the centre becomes weak.
• Check containers frequently in warm weather and keep their drainage holes clear.

Pruning. Cut dead foliage back to a few inches above the crown in late winter or early spring, before new shoots lengthen. Avoid cutting into emerging green growth.

Late winter

Remove collapsed dead foliage before new shoots emerge; leave standing foliage longer if it still looks attractive.

Spring

Plant or divide as growth starts, then water thoroughly.

Mid-spring

Top-dress with compost and renew the moisture-conserving mulch.

Summer

Water during dry spells and check container plants frequently for drying out.

Autumn

Leave bronze foliage standing for seasonal colour unless it becomes untidy.

Winter

Check that containers drain freely and shelter pots from severe freezing in colder regions.

• Edge a shaded path with repeated clumps so the arching leaves soften paving and stone.
• Plant beneath open-canopied trees with ferns and hostas for contrasting leaf shapes, provided tree roots do not dry the soil.
• Use in a wide container where the foliage can spill over the rim.
• Mass on a moist, shaded bank to create a low, flowing ground layer.

Garden styles it suits: Japanese, Woodland, Japandi, Modern courtyard, Sensory garden and Pacific Northwest woodland.

Plant it with: Hostas, Japanese painted ferns, Epimediums, Hellebores, Astilbes and Brunnera.

Wildlife: Clumps provide some shelter for small invertebrates. Flowers are wind-pollinated and are not a significant nectar source for bees or butterflies.

• Brown leaf tips or scorched patches: check soil moisture, water deeply and provide protection from hot afternoon sun and drying wind.
• Yellowing and crown decline in wet soil: improve drainage or move the plant; do not leave containers standing in water.
• Weak growth beneath trees: reduce competition where practical, add compost and provide reliable irrigation, or move to a less crowded site.
• Slug or snail damage to young shoots: inspect new growth and use hand-picking, barriers or a locally approved control if needed.

Not known to be toxic to cats, dogs, horses or people, and no part is recognised as poisonous. Species-specific information, particularly for horses, is limited; it should not be treated as food or livestock forage.

• Japanese sedge (Carex morrowii)

  Usually retains its leaves through winter and forms a more upright, basal fountain. Japanese forest grass has leaves spaced along slender, arching stems and dies back in winter.

• Northern sea oats (Chasmanthium latifolium)

  Has broader leaves, taller upright stems and conspicuous dangling, flattened seedheads. Japanese forest grass stays lower and has fine, airy flower sprays.

Hakonechloa combines Hakone, a mountainous area of Japan, with the Greek word for grass, while macra means large or long.

Propagation. Divide established clumps in spring as growth begins, keeping several shoots and a good portion of roots in each piece. Replant promptly and keep moist. Division preserves the colouring of named cultivars; seedlings may differ.

Accepted botanical name

Hakonechloa macra

In the US and Canada

Introduced in the lower 48 states.

Native range

Japan.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.