Common bistort

Common bistort: how do you recognise it?

Habit

Dense, slowly spreading mat of broad leaves, with flower stems up to about 60 cm.

Leaves

Large, oval to oblong, up to about 20 cm long, with a pale midrib; the underside is bluish green.

Flower

Dense, cylindrical spikes on unbranched stems, from May to July.

Colour

Soft pink; ‘Superba’ has slightly brighter pink spikes.

Roots

Thick, S-shaped twisted rhizomes, which gave the plant its name.

Flowering: May–July · Plants: March–May and September–October · Pruning: March and July

Why grow it?

• A native plant for moist soil, a pond edge or a natural border.
• Pink spikes from May to July, and often a second flush if you cut back after the first.
• A dense ground cover that gives weeds little chance.
• Bees, bumblebees and hoverflies visit the flower spikes.
• Also grows in heavy clay and wet soil.
• Tough and long-lived, with few disease problems.

Common bistort: where does it grow best?

• Sun to partial shade; in full sun the soil must stay moist.
• Moisture-retentive, humus-rich soil: loam, clay or peat, acid to neutral.
• Moist to wet: ideal at a pond edge, in a river valley or in a damp border.
• Plant 40–50 cm apart; 4–5 plants per m² knit together into a dense mat.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Acid or neutral

Moisture

Normal or wet

Size

0.6 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Siberian iris: Narrow leaves and blue flowers in the same moist soil, in May–June.
• Astilbe: White and pink plumes in summer, also for moist soil in partial shade.
• Hosta: Large leaves as a calm contrast.
• Meadowsweet: Creamy, fragrant plumes in June–July, also native.
• Purple loosestrife: Purple-pink spikes in summer, when the bistort has finished flowering.

Common bistort: when and how to plant it?

Plant in March–May and September–October.

1. Plant from March to May or in September–October, when the soil is not frozen.
2. Dig a hole twice as wide as the root ball and mix in compost or leaf mould.
3. Set the plant at the same depth as it was in the pot and firm the soil well.
4. Leave 40–50 cm between plants.
5. Water in well straight away and keep the soil moist during the first year.
6. Spread leaf mould as a mulch around the plants.

Care

Water

Never let the soil dry out; water generously in dry summers. In drought the leaves get brown edges.

Feeding

A layer of compost in spring.

Mulching

Leaf mould or compost in March keeps the soil moist.

Cutting back

After the first flush, cut back the spent spikes and tired leaves: you get fresh leaves and often a second flush.

Dividing

Every 4–5 years, or when the mat gets too big.

Tip: In July, cut back the spent spikes and tired leaves and water: you get fresh leaves and often a smaller second flush in late summer.

Common bistort: when to prune it?

Pruning months: March and July.

When: After the first flush, in July, cut away the spent stems for a second flush. In March, tidy away the old, dead leaves.

How:

• In July, cut the spent flower stems off at the base.
• If the leaves look tired or brown, cut them back too, then water and give a little compost.
• In March, cut away last year’s dead leaves, just above the new shoots.

Caution: In a dry summer, only cut back if you can water afterwards.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In March–April or in September–October: chop a piece of the mat with rhizome and shoots and replant it elsewhere straight away.

Seed

Possible for the species, but division is much quicker. Propagate cultivars such as ‘Superba’ by division so they stay true.

Common bistort: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: no protection is needed in Belgium.
• The leaves die back in late autumn; it regrows in spring.
• It copes well with wet soil in winter.

Diseases and pests

• Drying out: Brown, scorched leaf edges in a dry summer. Water and mulch, or move it to a damper spot.
• Slugs: They eat the young leaves in spring. Pick them off in the evening.
• Powdery mildew: White powder on the leaves in late summer, especially in dry weather. Water and cut back.
• Spreading: In wet, rich soil the mat spreads considerably. Chop off the edges in spring.

Through the year

• March: Cut away old leaves. Add compost. Plant and divide.
• April: Plant. Watch for slugs.
• May: Flowering begins. Plant.
• June: Full flower. Water in dry spells.
• July: Cut back spent stems and tired leaves. Water and add compost.
• August: Fresh leaves, sometimes a second flush. Water in dry spells.
• September: Plant and divide.
• October: Plant and divide.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The name bistorta means ‘twice twisted’ and refers to the S-shaped rhizome; the Dutch name adderwortel, ‘adder root’, also refers to this snake-like shape.
• In the north of England the young leaves were traditionally used in a spring pudding.
• Persicaria means ‘peach-like’: the leaves of many species resemble those of the peach.