Common bistort

How to recognise it

Growth habit

Perennial, 30–80 cm, forming wide clumps from thick rhizomes.

Leaves

Oblong-oval, 10–20 cm, with a squared or heart-shaped base and a winged stalk; green above, bluish grey beneath.

Flowers

A dense, cylindrical spike of 3–7 cm made up of tiny pale pink flowers, on an unbranched, almost leafless stem; May to July.

Fruit

A small, shiny brown, three-sided nut.

Roots

A thick, S-shaped twisted rootstock, reddish inside.

Look-alikes

Amphibious bistort grows in or beside water and has shorter, thicker spikes on a leafy stem. Redshank and pale persicaria are annuals with branched stems and smaller spikes. Common bistort has a single fat spike on a long, bare stem.

Flowering: May–July · Pruning: March, July and September

Why grow it?

• Food plant of the violet copper, a rare butterfly that in Belgium lives almost only in wet Ardennes hay meadows with bistort.
• The pink spikes are full of nectar and busy with bees, bumblebees and hoverflies.
• Its rhizomes form a dense mat that smothers weeds: ideal for wet ground where few other plants thrive.
• A long flowering season from May to July, with fresh green leaves into autumn.
• The young leaves were once eaten, for example in a traditional herb pudding in northern England.

Common bistort: where does it grow best?

• In the wild: moist to wet hay meadows, stream banks, tall-herb vegetation and wet woodland edges, especially in cool, rainy regions.
• In the garden: sun or half shade; the sunnier the spot, the wetter the soil must be.
• Humus-rich, moist to wet soil, preferably slightly acid: clay, loam or peaty soil.
• Lovely beside a pond, in a damp corner or as ground cover between light shrubs.

Goes well with

• Meadowsweet: Creamy plumes on the same wet soil, flowering just after bistort.
• Ragged-robin: Frilly pink flowers in May–June in the same damp meadow.
• Great burnet: Dark red heads in summer; a classic partner in wet hay meadows.
• Cuckooflower: Flowers pale lilac in April, before bistort starts.
• Water forget-me-not: Sky-blue flowers at the water’s edge.

Common bistort: when and how to plant it?

1. Buy plants from a native plant nursery. Never dig up bistort from the wild.
2. Plant in March–April or September–October, 40–50 cm apart; four to six plants per m² soon form a closed carpet.
3. Work some compost or leaf mould into the planting spot if the soil is poor and dry.
4. Plant at the same depth as in the pot and water generously.
5. Keep the soil moist in the first year; a mulch of leaf mould helps.

Care

Watering

Never let it dry out: on dry soil the leaves turn brown. Water during dry summers.

Feeding

A thin layer of compost in spring is enough.

Mowing

In a hay meadow, mow once in September, after flowering, and remove the cuttings. Always leave part unmown for butterflies.

Spreading

It spreads steadily by rhizomes. Slice off the edges with a spade in spring if it gets too big.

Faded spikes

Cut them off in July; the clump stays tidier and sometimes produces a few late flowers.

Tip: Plant bistort where the soil stays moist in summer, such as the low end of the garden or next to an overflowing water butt: there it becomes a beautiful pink carpet.

Pruning and mowing

Pruning months: March, July and September.

When: Clear old leaves in March, cut faded spikes in July, mow meadows in September.

How:

• Cut faded flower stems off at the base in July.
• Leave the dead leaves lying over winter: they protect the rhizomes.
• Remove the old leaves in March before the new ones emerge.
• In a hay meadow: mow at 5–10 cm in September and remove the cuttings.

Caution: To help butterflies, never mow everything at once: always leave part standing.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or September, slice off a piece of rhizome with a few buds and replant it elsewhere. This is very easy.

Seed

Sow fresh seed outdoors in autumn in a pot of moist compost; it germinates in spring. Slower than division.

Common bistort: how does it get through the winter?

Hardy to −30 °C.

• The leaves die back and turn brown; the rhizome survives the winter underground.
• Very hardy, to about −30 °C: no problem at all, even in the high Ardennes.
• Leave the dead leaves to protect the buds and to shelter small creatures.

Diseases and pests

• Spreading: On moist soil it spreads quickly. Slicing around it with a spade keeps it in check.
• Brown leaves: A sign of drought or too much sun. Water, or move it to a damper spot.
• Slugs: They eat young leaves in spring; the plant usually grows away quickly.
• Few flowers: Too much shade or too dry. A lighter, moist spot helps.

Through the year

• March: Clear old leaves. Plant or divide.
• April: New leaves; add compost.
• May: First pink spikes.
• June: Full flower; lots of bees and bumblebees.
• July: End of flowering; cut off faded spikes.
• August: Water during dry spells.
• September: Mow the meadow and remove the cuttings. Plant, divide or sow.
• October: Planting time.
• November: The leaves die back; leave them lying.
• December: Dormant.

Did you know?

• Bistorta means ‘twice twisted’ and refers to the contorted rootstock; the Dutch name ‘adderwortel’ (adder root) and the old English name snakeweed refer to the same snake-like shape.
• In northern England a herb pudding was made in spring with the young leaves: Easter-ledge pudding.
• In Belgium the violet copper depends entirely on bistort: without well-managed wet hay meadows the butterfly disappears.