Water violet

Water violet: how do you recognise it?

Habit

Submerged, partly floating stems rooted in the mud; the flower stems rise 20–30 cm above the water. A clump grows to about 50 cm across.

Leaves

Comb-like, finely divided into narrow segments, light green, spaced along the stems and entirely underwater.

Flowers

Whorls of three to eight flowers about 2 cm across, in tiers along a sturdy, leafless stem, in May and June.

Colour

Pale pink to lilac, sometimes almost white, with a yellow eye.

Roots

Fine roots, partly in the pond bottom and partly hanging free in the water.

Flowering: May–June · Plants: April–June · Pruning: July

Why grow it?

• One of the loveliest flowering oxygenators: in May and June a field of pale pink flower spikes above the water.
• The fine underwater foliage takes up nutrients and releases oxygen, which holds back algae.
• Native: perfect for a wildlife pond with clear water.
• Bees and hoverflies visit the flowers; tadpoles, water beetles and young fish shelter in the foliage.
• Also grows in light shade, where many other aquatic plants struggle.

Water violet: where does it grow best?

• Sun or partial shade; it tolerates more shade than most aquatic plants.
• Clear, still, low-nutrient water, acid to neutral: rainwater is ideal, hard tap water is not.
• Planting depth 20–50 cm below the water surface, in the shallow to deeper water zone.
• A basket or the pond floor with a thin layer of poor soil: loam, clay or peat, without fertiliser.
• Allow about 50 cm per bunch and keep vigorous spreaders away, as they will crowd it out.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Acid or neutral

Moisture

Wet

Size

0.3 m tall, 0.5 m wide

Hardiness

Hardy (to -25 °C)

Goes well with

• Bogbean: Fringed white flowers at the edge, in the same poor, acid to neutral water.
• Frogbit: A small floating plant that gives the water a little shade in summer.
• Water forget-me-not: Blue flowers at the margin while the water violet blooms further out.
• Pygmy water lily: White flowers in summer, once the water violet has finished.

Water violet: when and how to plant it?

Plant in April–June.

1. Plant from April to June, in clear water that is starting to warm up.
2. Fill an aquatic basket with low-nutrient aquatic compost or sandy loam, with no potting compost or fertiliser.
3. Push the stems and their roots 3–5 cm into the soil and firm them in; a few pebbles will hold loose stems in place.
4. Top with a little gravel and lower the basket slowly to 20–50 cm deep.
5. Leave about 50 cm between bunches or baskets.
6. Be patient: in the first year it often grows slowly and flowers little.

Care

Water

Top up with rainwater, not hard tap water, which often contains nutrients too.

Feeding

Never: in nutrient-rich water it disappears under algae and fast growers.

Algae

Remove blanketweed promptly, as it can smother the fine leaves.

Spent flowers

Cut off the faded flower stems in July, or leave a few to set seed.

Peace and quiet

Do not keep lifting it out of the water: it does best when left undisturbed.

Tip: Top up your pond only with rainwater and never feed it: in clear, low-nutrient water the water violet will thrive for years.

Water violet: when to prune it?

Pruning months: July.

When: Hardly any pruning is needed. In July, cut off the faded flower stems and thin out if it becomes too dense.

How:

• Cut faded flower stems off just above the water.
• Pull out overcrowded stems by hand; always leave at least half the plant.
• Leave cut material on the bank for a day so small creatures can return to the pond.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Stem cuttings

From May to August, break off 10–15 cm pieces of stem and push them into a basket of poor soil or weight them to the bottom with a pebble. In clear water they root readily.

Division

In April–May, split a rooted clump and plant the pieces in a new basket.

Water violet: how does it get through the winter?

Hardy to −25 °C.

• Hardy to about −25 °C: the plant overwinters underwater.
• No protection needed as long as there is water left under the ice; in a pond at least 50 cm deep that is no problem in a Belgian winter.
• In a small tub everything can freeze: move the tub to a cool, frost-free place for the winter and keep the water topped up.

Diseases and pests

• Disappears after a year: Often a sign of water that is too rich or too hard. Top up with rainwater, use poor soil and do not feed.
• Blanketweed: Smothers the fine leaves. Gently twist the strands away with a stick.
• Few flowers: Too much shade or a young plant. In a lighter spot and after a year or two it flowers more freely.
• Fish: Goldfish and carp eat the fine leaves and churn up the soil. In a heavily stocked pond it struggles to survive.

Through the year

• April: Plant or divide in clear water.
• May: Flowering begins. Take cuttings.
• June: Full flower. Last month for planting.
• July: Cut off faded flower stems. Thin out if too dense.
• August: Remove blanketweed. Top up with rainwater.
• October: Net fallen leaves out of the pond.
• December: Resting underwater.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• As in primroses, there are two kinds of flower, with a long or a short style; this way plants pollinate each other rather than themselves.
• It is one of the few true aquatic plants in the primrose family.
• The name Hottonia honours the Dutch botanist Petrus Hotton, who worked in Leiden around 1700.