Why Are My Indocalamus Leaves Curling?

Drought and water stress

The very large leaf surface area creates an exceptionally high transpiration rate; even a brief dry spell causes the enormous leaves to curl and droop limply, a visually very dramatic response. In containers, the leaves can show rolling and drooping within a few hours of the compost drying out in hot weather. The plant is naturally adapted to consistently moist, sheltered, forest-understorey conditions.

What to do

• Water deeply and thoroughly in dry spells throughout the growing season; check containers at least daily in summer (more often in hot weather); incorporate large quantities of well-rotted compost and leaf mould into the soil at planting to improve moisture retention; apply a deep mulch (10 to 15 cm) of composted bark or leaf mould around the base each autumn; a sheltered, partially shaded or dappled-shade position in moisture-retentive humus-rich soil is far more drought-resilient than full sun or an exposed position with thin, dry soil.

Wind desiccation

The very large, broad leaves present an enormous surface to the wind; persistent drying winds in summer or cold easterly winds in late winter and spring strip moisture faster than the root system can replace it; the result is similar to drought stress with rolling, drooping, and leaf tip and margin browning. Most severe in February and March when cold soil temperature further slows water uptake.

What to do

• Plant in a sheltered position away from prevailing winds; the natural forest-understorey habitat of indocalamus provides shelter from wind; a position on the sheltered side of a building, fence, hedge, or established planting reduces wind desiccation damage significantly; a permeable windbreak is more effective than a solid fence (which creates turbulence); cut back any dead or damaged culms from wind desiccation in spring after the risk of further frost has passed.

Cold and frost stress

Hardy to approximately -15 to -18°C in well-established, sheltered positions; in the coldest UK winters or very exposed positions, the large leaves may suffer frost damage beyond normal cold-triggered protective curling, browning and drying at the tips and margins. The culms and rhizomes are generally more frost-hardy than the leaves and the plant usually regenerates from the root system in spring even after severe leaf and culm die-back.

What to do

• Cut back old or frost-damaged canes to ground level in late winter to encourage vigorous new cane production in spring; this is the most effective single maintenance action for indocalamus and also the best recovery treatment after frost damage; apply a thick mulch over the root zone in cold positions to protect the rhizomes. Cut back annually even without frost damage to maintain the production of the largest, most spectacular new leaves on the newest, most vigorous canes.

Frequently asked questions

Why are my indocalamus leaves curling?

Indocalamus leaves curl most commonly because of drought and water stress (very large leaf surface creates exceptionally high transpiration rate; even brief dry spells cause dramatic rolling and drooping; container plants can droop within hours of compost drying; water deeply and frequently; daily container checks; incorporate compost and leaf mould for moisture retention; deep mulch each autumn; sheltered partially shaded moisture-retentive position far more resilient), wind desiccation (enormous leaf surface area vulnerable to drying winds; most severe in February to March with cold easterly winds and cold soil slowing water uptake; plant in sheltered position; permeable windbreak; cut back damaged culms in spring), or cold and frost stress (hardy to approximately -15 to -18°C in sheltered positions; large leaves suffer frost damage beyond normal protective curling in severe winters; culms and rhizomes more frost-hardy; cut back damaged canes to ground level in late winter for new vigorous spring growth). Annual cane cutback is the best single maintenance action.

How do I keep indocalamus looking its best in a UK garden?

Position: sheltered partially shaded or dappled-shade position; naturally grows in woodland understorey; full sun causes maximum evaporative stress and leaf curl; north or east facing or dappled shade under deciduous trees far better; sheltered from prevailing cold winds. Soil and moisture: moisture-retentive humus-rich deep soil; large quantities of well-rotted compost and leaf mould at planting; deep mulch (10 to 15 cm) of composted bark or leaf mould each autumn over the spread of rhizomes. Watering: deeply in dry spells; daily container checks in summer. Annual maintenance: cut back all old tatty or damaged canes to ground level in late winter; encourages production of fresh vigorous new canes with the largest most spectacular new leaves in spring; newest most vigorous canes bear the largest leaves.

Does indocalamus tessellatus spread and is it invasive?

Spread: intermediate between tight clumping fargesia and strongly running phyllostachys; more spreading than fargesia; much less aggressive than most vigorous phyllostachys; typically spreads outward 15 to 30 cm per year in UK conditions. Management: root barrier (40 to 60 cm depth adequate; less than the 70 to 80 cm required for vigorous phyllostachys) installed before planting; or annual spade cut around perimeter in autumn or spring; container growing also effective though drought stress more likely. UK law: not listed on Schedule 9 of the Wildlife and Countryside Act 1981; not a notifiable invasive species; not the same legal risk as Japanese knotweed. Best uses: dramatic low-growing ground-cover in large gardens or woodland gardens where spreading is acceptable; or root-barrier-contained planting in smaller gardens.

What is the difference between indocalamus and sasa?

Similarities: both low-growing (0.5 to 1.5 m in UK); both very broad large paddle-shaped leaves; both spread via rhizomes; both used as dramatic ground-cover; both prefer sheltered moist partially shaded position. Key differences: leaf size: I. tessellatus has the largest leaves of any commonly grown UK temperate bamboo, regularly 50 to 60 cm long and up to 10 cm wide; Sasa palmata up to 35 cm long and 8 cm wide. Branch number: Indocalamus typically single branch per node; Sasa multiple branches per node. Spread rate: Sasa palmata generally more vigorously spreading in UK conditions than I. tessellatus. S. veitchii winter effect: the characteristic pale straw-coloured papery dried leaf margins in autumn and winter in S. veitchii are unique and not seen in I. tessellatus.