Dwarf bulrush

Dwarf bulrush: how do you recognise it?

Habit

Slender, upright clumps 30–60 cm tall and about 40 cm across, slowly spreading by short runners.

Leaves

Very narrow and grass-like, barely a few millimetres wide; they turn yellowish brown in autumn.

Flowers

At the top of the stem, a narrow, light brown male spike that withers soon after shedding its pollen; below it, a small round to oval female head a few centimetres long.

Fruit

The head turns dark brown and breaks up in autumn or winter into white fluff that carries tiny seeds on the wind.

Roots

A creeping rhizome just below the surface, less vigorous than that of the great bulrush.

Flowering: June–August · Plants: April–June · Pruning: March

Why grow it?

• The only bulrush small enough for a small pond, a tub or a mini pond on the patio.
• Charming round brown heads from June into autumn, a lovely alternative to the big cigar-shaped ones.
• Its fine, grass-like leaves add a light, vertical touch to the pond edge.
• The heads look lovely in dried arrangements.
• Spreads far less than the great bulrush and is easy to keep in check in a basket.
• Upright stems that dragonfly larvae can climb to leave the water.

Dwarf bulrush: where does it grow best?

• Full sun; in shade it produces few heads.
• Wet, fertile soil: loam, clay or peat; pH does not matter.
• At the pond edge or in shallow water, with 0–15 cm of water above the soil in the basket.
• Allow 30–40 cm per plant; in a tub or mini pond, one plant is enough.

Light

Sun

Soil type

Loam, clay or peat

Acidity

Not fussy

Moisture

Wet

Size

0.6 m tall, 0.4 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Dwarf water lily: Floating flowers on the open water, even in a small pond or tub.
• Bogbean: White flowers in May and creeping stems in the same shallow water.
• Water forget-me-not: Small blue flowers at the foot of the slender stems.
• Marsh marigold: Golden yellow flowers in spring, long before the heads appear.

Dwarf bulrush: when and how to plant it?

Plant in April–June.

1. Plant from April to June, once the water has warmed up a little.
2. Use a pond basket filled with heavy garden soil or clay-rich aquatic compost; no potting compost or fertiliser, as they feed algae.
3. Set the rhizome just below the surface, firm it in and top with a layer of gravel so the soil does not wash out.
4. Place the basket so there is 0–15 cm of water above the soil; stand it on a few stones if needed.
5. Leave 30–40 cm between plants. On the bank, make sure the soil always stays wet.

Care

Watering

It must always stand in water or in wet soil. Top up the pond in dry summers, preferably with rainwater.

Feeding

Not needed: it takes enough nutrients from the water. Fertiliser turns the water green.

Dividing

Every 3–4 years, when the basket is full, divide the clump in April–May and replant.

Seed heads

Cut heads for drying in August, when they are brown and firm.

Old foliage

Leave the dead foliage standing over winter and cut it back in March, above the water line.

Tip: Cut heads for dried arrangements in August, as soon as they are brown and firm: later on they break up into fluff indoors.

Dwarf bulrush: when to prune it?

Pruning months: March.

When: In March, before the new leaves appear. Otherwise it needs hardly any pruning.

How:

• Cut dead foliage and old stems back to just above the water line or the soil.
• Fish loose leaves and stems out of the water so they do not rot.
• If you want no seedlings or fluff in the pond, cut off the heads you are not drying before they break up.
• Remove runners growing over the edge of the basket.

Caution: Never cut the stems below the water line: the hollow stems fill with water and the rhizome may rot.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In April–May, lift the basket, cut the rhizome with a sharp knife or spade into pieces, each with a few shoots and roots, and plant each piece in its own basket.

Seed

In spring, scatter seed on wet, sandy compost and press it in lightly without covering it. Keep the compost wet, for instance by standing the pot in a saucer of water. Seedlings grow slowly.

Dwarf bulrush: how does it get through the winter?

Hardy to −25 °C.

• Fully hardy to about −25 °C: no protection needed in a pond.
• Leave the dead foliage until March: it protects the rhizome, and the heads decorate the pond in winter.
• In a small tub the water can freeze solid: move it against a sheltered wall or into an unheated shed, and never let the soil dry out.

Diseases and pests

• Aphids: Black or green aphids on the stems and leaves, mainly in summer. Hose them into the water, where fish eat them.
• Runners escaping the basket: The rhizomes grow over the edge into the pond. Cut them off or divide the plant when the basket is full.
• Fluff in the pond: Ripe heads break up into fluff in autumn or winter. Cut them off in time if you do not want that.
• Few heads: Too little sun or an overcrowded basket. Move it to a sunnier spot and divide the clump.

Through the year

• March: Cut dead foliage and old stems back to above the water line.
• April: Plant or divide. New leaves appear.
• May: Plant or divide. Watch for aphids.
• June: Plant. The first heads appear.
• July: Flowering. Top up the pond in dry spells.
• August: Cut brown heads for drying.
• September: The heads decorate the pond edge.
• October: The foliage turns yellowish brown. Leave it standing.
• December: Rest. Fish fallen leaves out of the water.

Did you know?

• In the wild it grows on bare sand and gravel banks along mountain rivers. Because rivers have been straightened and embanked, it has become rare in many places.
• Each stem carries two kinds of flower: at the top a narrow male spike that sheds pollen and withers, below it the brown female head.
• The seeds have fine hairs and drift away on the wind as fluff, just like those of the great bulrush.