Bulrush

Bulrush: how do you recognise it?

Habit

Upright clumps up to 2 m tall, spreading by rhizomes into dense stands 1 m across and much more.

Leaves

Long and strap-shaped, 1–2.5 cm wide, blue-green and flat.

Flowers

From June to August a straight spike: yellow male flowers at the top, the female head directly below. They are wind-pollinated.

Seed head

Thick, dark brown, cigar-shaped head of 10–20 cm that bursts in winter into white fluff full of seeds.

Roots

Thick, creeping rhizomes with sharp tips that can pierce a pond liner.

Pond zone

Marsh zone and shallow water: from 0 to 40 cm below the water surface.

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

Why grow it?

• Thick, dark brown heads from summer into winter: a classic for the wildlife pond.
• Lovely in dried arrangements if you cut the heads in time.
• Reed birds such as the reed warbler and reed bunting nest in large stands, and moorhens build their nests there.
• Dragonflies and damselflies climb out of the water up the stems, and insects overwinter in the stems.
• Grows fast and takes up plenty of nutrients: a help against algae in a large pond.
• Native and fully hardy.

Bulrush: where does it grow best?

• Full sun.
• A rich bottom of loam, clay or peat; acid, neutral or alkaline all suit it.
• Water depth 0–40 cm, in still or slow-moving water, or on a wet bank.
• Only for a large pond or a natural bank without liner; otherwise in a rigid container.
• Allow at least 1 m per plant.

Light

Sun

Soil type

Loam, clay or peat

Acidity

Not fussy

Moisture

Wet

Size

2 m tall, 1 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Yellow flag: Yellow flowers in May–June in the shallower zone in front.
• Water lily: Round floating leaves and flowers in the deeper open water.
• Yellow water lily: A vigorous native floating-leaved plant for the deep water of a large pond.
• Purple loosestrife: Purple spikes on the bank, excellent for bees and butterflies.

Bulrush: when and how to plant it?

Plant in April–June.

1. Plant from April to June, when the water warms up.
2. On a natural bank plant straight into the mud. In a lined pond use a rigid container of at least 30 litres without holes in the sides.
3. Fill it with heavy clay soil, without potting compost or fertiliser, lay the rhizome about 5 cm deep and top with 2–3 cm of gravel.
4. Stand the container at 10 cm depth first and lower it after a few weeks to no more than 40 cm below the water surface.
5. Keep at least 1 m from other plants.

Care

Water

Not needed in the pond. In dry summers top up the pond with rainwater.

Feeding

Do not feed: it is vigorous enough already and fertiliser feeds the algae.

Keeping in check

Check the rim of the container every summer and cut off rhizomes growing over it. On a natural bank dig out part of it every year.

Drying heads

Cut heads for arrangements in July–August, when they have just turned brown: riper heads burst into fluff indoors.

Dividing

Every 2–3 years, when the container is full, divide in April–May.

Tip: Only choose it for a large pond or a natural bank, or plant it in a rigid container without holes in the sides: that way your liner and the rest of the pond are spared.

Bulrush: when to prune it?

Pruning months: March.

When: In March, before the new shoots appear. Leave leaves and heads standing over winter.

How:

• Cut the old, brown stems and leaves off above the water surface, not below it.
• Remove leaves that fall into the water in autumn earlier, so they do not rot on the bottom.
• Cut off the heads in autumn if you want to avoid the fluff spreading seeds everywhere.
• On a natural bank cut a different section each year, so there is always shelter left for birds and insects.

Caution: Do not cut too late in March: the new shoots grow fast and break easily.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In April–May lift the plant from its container or the bank and cut the rhizome with a sharp spade into pieces with a few shoots each. Replant straight away.

Bulrush: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Belgium.
• Leave leaves and heads until March: insects overwinter in the stems and birds shelter among them.
• In late winter the heads burst open and the fluff carries the seeds away.

Diseases and pests

• Spreading too much: Within a few years it covers the whole bank. Dig out rhizomes, check the container and divide every few years.
• Leaking pond: The sharp rhizomes have pierced the liner. Always plant in a rigid container and do not choose it for a small lined pond.
• Fluff indoors: Dried heads burst open inside. Harvest them earlier, when they have just turned brown.
• Pond silting up: It takes over the open water and the pond fills in. Remove part of it every year, rhizomes and all.

Through the year

• March: Cut old stems and leaves off above the water surface.
• April: Plant or divide. New shoots appear.
• May: Plant. Set the container at the right depth.
• June: In flower. Cut off rhizomes outside the container.
• July: In flower. Cut heads for drying.
• August: Cut heads for drying. Top up the pond in dry spells.
• October: Take fallen leaves out of the water.
• December: Leave leaves and heads for birds and insects.

Good for wildlife

Birds

Berries, seeds or insects as food, or a place to nest.

Did you know?

• In bulrush the yellow male part of the spike sits directly on the brown head; in lesser bulrush there is a bare piece of stem between them.
• Coopers once used bulrush leaves to make the joints between the staves of barrels watertight.
• The caterpillars of some moths live inside bulrush stems and eat them from within.