Persicaria amphibia, known as amphibious bistort, is a UK native that grows either in water, with glossy leaves floating on the surface, or on wet ground. From June to September it holds short spikes of pink flowers just above the water.

Amphibious bistort at a glance

Botanical name Persicaria amphibia
Common name Amphibious bistort, water knotweed
Plant type Floating-leaved or creeping perennial; dies back in winter
Height and spread Flowers 10–50 cm above water; spreads up to 1 m
Flowers Pink, in short dense spikes, June to September
Position Full sun or part shade (flowers best in sun)
Soil Water or wet soil
Pond depth 15–90 cm of water (about 45 cm is ideal); also grows in wet soil
Hardiness RHS H7 – very hardy (below -20°C)
Native to UK and Ireland (native wild flower)

How deep should amphibious bistort be planted?

In water it does best at about 45 cm, and will grow anywhere from 15 cm to 90 cm deep. Lower deeper plants in stages so the leaves can reach the surface. It also grows on wet ground, but flowers far less there.

Is it good for wildlife?

Yes. It is on the RHS Plants for Pollinators list, and the floating leaves give surface cover in native ponds.

Does it spread?

Yes. The RHS notes it can become a nuisance if not managed. Grow it in a basket and divide it regularly.

Which size should I buy?

Bare-root plants (7 cm, 9 cm, 1 litre and 3 litre) arrive without a pot or compost and are the most economical way to plant a group. Potted plants (9 cm, 1 litre and 3 litre) arrive growing in our peat-free compost and give a faster display. Packs of 3 cost less per plant. The 2x Pot & Compost option is two plants supplied with pots and compost.

Pond depth: 0 - 100cm

Light: Full sun or part shade

Hardiness: Hardy

Height and spread: 20 - 40cm tall, 50 - 100cm wide

Planting and flowering months are shown in the calendar under the photos.

Bare root (7 cm, 9 cm, 1 litre, 3 litre): plants sent without a pot or compost, ready to plant straight away. The most economical way to plant a group.

Potted (9 cm, 1 litre, 3 litre): plants growing in our recycled, peat-free compost made in Lincolnshire. Larger sizes give a faster display.

Pack of 3 (7 cm bare-root, 9 cm bare-root, 1 litre bare-root, 3 litre bare-root): three plants of the chosen size at a lower price per plant.

2x Pot & Compost: two plants supplied with pots and compost.

Sizes shown with a line through them are currently unavailable.

At Lincs Plants, we strive to provide fast and reliable shipping to ensure your plants arrive in perfect condition. We offer 1-3 day shipping through a variety of dispatch methods to suit your needs.

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