Common cottongrass

How to recognise it

Habit

Upright sedge of 20–60 cm that forms loose patches from creeping rhizomes, not dense tussocks.

Leaf

Narrow, 2–6 mm wide, channelled, ending in a long, three-angled tip; red to purplish brown in autumn.

Flower

In April–May, 3–7 nodding spikelets at the top of the stem on smooth stalks of unequal length; inconspicuous, brownish green, with yellow anthers.

Fruit/Seed

After flowering, the bristles around each flower grow into white hairs of 3–5 cm: the cotton. Among them sit small brown nutlets, which blow away with the cotton in June–July.

Stem

Round, bluntly three-angled near the top, smooth and without nodes.

Confusion with

Hare’s-tail cottongrass forms dense tussocks and carries only one upright tuft per stem. Broad-leaved cottongrass has wider, flat leaves and rough flower stalks and grows on more calcareous soil; it is very rare in Belgium.

Flowering: April–May · Pruning: March

Why grow it?

• From May to July, spectacular white tufts that light up a wet corner or pond edge.
• Cottongrasses, especially hare’s-tail cottongrass, are the foodplants of the large heath, a rare butterfly of raised bogs.
• A pioneer on bare, wet peat: it helps restore bogs and heathland pools.
• The narrow leaves turn red to purplish brown in autumn.
• A piece of real bog in your garden: in a small bog garden or at the edge of a rainwater pond.
• In the past the cotton was used locally to stuff pillows and as lamp wicks.

Common cottongrass: where does it grow best?

• In the wild: raised bogs, wet heath, the edges of heathland pools, peaty fens and wet, acid grassland.
• Full sun; in shade it hardly flowers.
• Wet to very wet, acidic, nutrient-poor soil, ideally peat or humus-rich sand; tolerates shallow water up to about 5–10 cm.
• In the garden: in a small bog garden or at the shallow edge of a rainwater pond, never on limy or fertilised soil.

Goes well with

• Cross-leaved heath: Pink bells in July–August on the same wet, acid soil.
• Round-leaved sundew: A small carnivorous plant that grows in bog moss among the cottongrass; only from a nursery.
• Marsh cinquefoil: Dark red flowers in June–July at the edge of acid pools.
• Sphagnum moss: Holds water like a sponge and is the basis of a real bog garden; never take it from the wild.
• Marsh violet: Small lilac violets in April–May on wet, acid soil.

Common cottongrass: when and how to plant it?

1. Buy plants from a nursery for aquatic or native plants. Never dig up plants or pick the cotton in the wild.
2. Plant in April–June in wet soil or in shallow water of 0–5 cm.
3. For a small bog garden, dig a hole 30–40 cm deep, line it with pond liner pierced with a few small holes and fill it with a poor, acid mix of sand and peat-free ericaceous compost or leaf mould. Do not use peat: peat cutting destroys the bogs where cottongrass grows.
4. Plant 30–40 cm apart, or 6–9 plants per m²; they soon join up.
5. Always keep the soil wet with rainwater, never with tap water: it is too limy.
6. You can also sow: sow fresh seed in summer or autumn on wet, acid soil, do not cover it, and leave the tray outdoors over winter.

Care

Watering

Keep it wet at all times with rainwater; top up from the water butt in dry summers.

Feeding

Never: cottongrass only grows on poor soil, and fertiliser makes room for grasses and soft rush.

Weeding

Pull out seedlings of soft rush, birch, willow and grasses in good time, before they overgrow the cottongrass.

Sun

Keep the spot open and sunny: cut back overhanging branches.

Spreading

In a small bog garden it can spread quite a bit. In spring, cut off pieces of rhizome if it becomes too much.

Tip: Give cottongrass only rainwater and not a single grain of fertiliser: poor, acid and always wet is the secret of a garden full of white cotton.

Pruning and mowing

Pruning months: March.

When: In March, before the new shoots appear; it is optional.

How:

• Cut the dead, brown leaves back to a few centimetres above the ground, or simply leave them.
• Remove the cut leaves so that the soil is not enriched.
• Leave the cotton tufts in June–July: the seed blows away and you enjoy them for longer.

Caution: Do not cut from April onwards: the flower spikelets are already appearing then.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In April–May, cut off pieces of rhizome with a few shoots and replant them elsewhere in wet, acid soil.

Seed

Collect ripe seed with its cotton from your own plants in June–July. Sow on wet, acid soil without covering, and leave outdoors over winter; germination is slow.

Common cottongrass: how does it get through the winter?

Hardy to −35 °C.

• In autumn the leaves turn red to purplish brown and die back; the rhizomes overwinter in the wet soil.
• Very hardy: it grows as far north as the Arctic.
• New shoots appear early in spring, and the first flowers in April.
• Leave the dead leaves over winter: insects and spiders shelter in them.

Diseases and pests

• No cotton: Too much shade or soil that is too rich. Grow it in full sun on poor, wet soil.
• Drying out: If the soil dries out, it withers. Always keep a bog garden wet with rainwater.
• Lime and fertiliser: Tap water, lime and fertiliser make the soil too rich: it fades away and gets overgrown. Use only rainwater and never fertiliser.
• Overgrowing: Soft rush, grasses and young trees outgrow it. Weed them out by hand in good time.

Through the year

• March: Cut away dead leaves (or leave them).
• April: New shoots and the first flower spikelets. Plant.
• May: In flower; the first white tufts appear. Plant or divide.
• June: White cotton tufts at their best.
• July: The seed blows away. Collect seed from your own plants.
• August: Top up with rainwater in dry spells.
• October: Leaves turn red to purplish brown.
• December: Dormant; the rhizomes overwinter in the wet soil.

Did you know?

• Eriophorum comes from the Greek erion, wool, and phoros, bearing: ‘wool-bearer’. Angustifolium means ‘narrow-leaved’.
• The white cotton consists of the lengthened bristles around each flower; it lets the seed float on the wind, far across the bog.
• Despite its name, cottongrass is not a grass but a sedge, a relative of the true sedges in the genus Carex.