Photo: Christian Fischer, CC BY-SA 3.0 · source
Water or marginal plant · Alismataceae
Water plantain
Alisma plantago-aquatica
In other languages: Grote waterweegbree (Nederlands) · Plantain d’eau (Français)
Water plantain is a native marginal plant of ditches, ponds and pond edges throughout Europe and much of Asia. A short, bulb-like rootstock produces a rosette of long-stalked, oval leaves with curved veins that recall those of plantain, which gives the plant its name. From June to September an airy, candelabra-like flower spray up to 80 cm tall rises above them, carrying dozens of small white to pale pink flowers that only open in the afternoon. Gardeners value it as an easy native plant for the marsh zone that flowers for months and attracts bees and hoverflies. It does self-seed readily.
Caution: The fresh plant, especially the rootstock, is poisonous if eaten. Children, dogs, cats and grazing animals such as cattle and horses are at risk: do not plant it by a drinking pond for livestock and do not eat any part of it. It also self-seeds strongly; never put plants or seed into natural waters.
Light
Sun or partial shade
preferably some sun
Moisture
Moist to wet
must not dry out
Legal basis
Loam, clay or peat
any pH
Hardiness
Fully hardy
down to -30 °C
Size
0.8 m
tall, 0.4 m wide
Flowering
June–September
| Pruning months | March and August–September |
|---|---|
| Height | 0.8 m |
| Native to Belgium | Yes |
| Good for bees, butterflies and birds | Yes, for bees |
| Poisonous to people and pets | Yes, take care with children and pets |
| Flowering | June–September |
Identify
Water plantain: how do you recognise it?
- Habit
- A leaf rosette 30–50 cm tall topped by a branched flower stem up to 80 cm.
- Leaves
- Long-stalked, oval to lance-shaped, with curved, parallel veins; under water it sometimes forms narrow, ribbon-like leaves.
- Flower
- Flowers about 1 cm across with three white to pale pink petals, in whorls on an airy spray, from June to September.
- Fruit
- A small ring of flat nutlets, which float and spread with the water.
- Roots
- A short, bulb-like rootstock with many fine roots in the mud.
Flowering: June–September · Plants: April–June · Pruning: March and August–September
In your garden
Why grow it?
- Flowers from June to September with airy, graceful sprays above the water.
- An easy native plant for the marsh zone of a wildlife pond.
- The small flowers attract bees, hoverflies and other small insects.
- The sturdy flower stems serve as a lookout for dragonflies and a ladder for dragonfly larvae climbing out of the water.
- The leaf rosette shelters tadpoles and other aquatic creatures in the shallows.
- Fully hardy and undemanding: grows in sun and partial shade, on loam, clay and peat.
Water plantain: where does it grow best?
- Sun or partial shade; it flowers best in full sun.
- In the marsh zone or in shallow water up to 15 cm deep.
- Loam, clay or peat, acid to chalky: it is not fussy.
- Allow 30–40 cm per plant; in a small pond, one plant is often enough.
- Light
- Sun and partial shade
- Soil type
- Loam, clay or peat
- Acidity
- Not fussy
- Moisture
- Wet
- Size
- 0.8 m tall, 0.4 m wide
- Hardiness
- Hardy (to -30 °C)
Goes well with
- Flowering rush: Pink flower umbels in the same summer, in the same shallow water.
- Arrowhead: A related native water plant with arrow-shaped leaves and white flowers.
- Marsh marigold: Flowers yellow in spring, long before the water plantain.
- Purple loosestrife: Purple-pink spikes on the wet bank, also loved by bees.
- Water forget-me-not: Small pale blue flowers at its feet, in the marsh zone.
Maintenance
Water plantain: when and how to plant it?
Plant in April–June.
- Plant from April to June, as the water warms up.
- Use an aquatic basket about 20 cm wide filled with heavy, low-nutrient aquatic soil; no potting compost or garden compost.
- Set the rootstock upright, with the centre of the rosette just above the soil, and firm in well.
- Top with a layer of gravel so the soil does not wash out.
- Lower the basket to 0–15 cm below the water surface, or plant into the wet soil of the marsh zone.
- Keep 30–40 cm between plants.
Care
- Water
- Must never dry out. In dry summers, top up the pond with rainwater.
- Feeding
- Not needed: fertiliser in the pond encourages algae.
- Deadheading
- Cut off the flower sprays after flowering to limit self-seeding. Leave one if you want to collect seed.
- Seedlings
- Pull unwanted seedlings from the bank while they are young and come out easily.
- Repotting
- Every 3–4 years, lift it from the basket, divide it and replant in fresh aquatic soil.
Tip: Plant it in the marsh zone up to 15 cm deep and cut off the flower sprays after flowering: that keeps self-seeding under control and the plant looks good for years.
Water plantain: when to prune it?
Pruning months: March and August–September.
When: Cut off the faded flower sprays in August–September, before the seed ripens. Cut away the dead foliage in March.
How:
- Cut the flower stems off at the base as soon as most of the flowers have faded.
- Leave dead foliage until March as shelter for insects, but fish out any leaves that fall into the water.
- In March, cut the remains of the old leaves back to just above the water.
Caution: Do not wait too long to remove the flower sprays: ripe seed drops, floats away and germinates all along the bank.
Propagation
- Seed
- Sow fresh seed in late summer in a pot of wet aquatic soil standing in a saucer of water, or in spring move a seedling that has come up by itself.
- Division
- In April–May, lift an old clump from its basket and divide it into pieces, each with its own leaf rosette and roots.
Water plantain: how does it get through the winter?
Hardy to −30 °C.
- Fully hardy, to about −30 °C: no protection needed.
- The foliage dies back in autumn; the rootstock overwinters in the mud.
- A basket in shallow water may freeze solid without harm.
Diseases and pests
- Self-seeding: Seedlings all along the bank and in other baskets. Cut off the flower sprays after flowering and pull seedlings while young.
- Aphids: Aphids on flower stems and leaves in summer. Hose them off with pond water; natural predators do the rest.
- No flowers: Planted too deep or in too much shade: it may then make only ribbon-like leaves under water. Raise the basket and give it more sun.
- Yellow leaves: In late summer the foliage dies back naturally: that is normal.
Through the year
- March: Cut away old leaf remains.
- April: Plant or divide.
- May: Plant. The new leaf rosette develops.
- June: First flowers. Plant.
- July: Full flower. Top up the water in dry spells.
- August: In flower. Cut off faded flower sprays.
- September: Last flowers. Cut off faded flower sprays. Sow fresh seed.
- October: Fish dead leaves out of the water.
- December: Rest.
Use
Edible and useful
Not edible. Fresh water plantain is poisonous, especially the rhizome: its acrid sap causes a burning mouth, vomiting and diarrhoea if swallowed, and can irritate the skin. Drying removes most of the acridity, but do not eat any of it all the same. Grazing animals such as cattle and horses are at risk if it grows by a drinking pond or ditch in their field: do not plant it there, and do not throw pulled-out plants into the field. Keep children, dogs and cats away too, and wear gloves when you take it out of the pond. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.
Good for wildlife
- Bees
- Nectar and pollen for honeybees and wild bees.
You and this species
Did you know?
- The small flowers only open in the afternoon and close again towards evening.
- Plantago-aquatica literally means ‘water plantain’, because the leaves look like those of plantain. The two are not related.
- The floating nutlets are spread by water and by waterbirds, which is how it turns up by itself in new ponds.