Yellow water lily

Yellow water lily: how do you recognise it?

Habit

Floating-leaved plant from a rhizome in the mud; a mature plant spreads to about 2 m or more.

Leaves

Oval to heart-shaped, 20–40 cm, leathery and glossy green, floating on the water; beneath them thin, wavy underwater leaves.

Flowers

Globe-shaped, 4–6 cm, on sturdy stalks up to 15 cm above the water, from June to August; the showy yellow parts are sepals.

Fruit

A green, flask-shaped fruit that ripens after flowering; the seeds are dispersed by water.

Rhizome

Thick, spongy and creeping; it can spread over several metres.

Flowering: June–August · Plants: May–June · Pruning: August–September

Why grow it?

• Robust and native: it grows where water lilies struggle, in partial shade and gently flowing water.
• Golden yellow globe-shaped flowers from June to August, with a sweet scent.
• The large floating leaves cast shade, keep the water cool and hold back algae.
• Frogs rest on the leaves, and damselflies such as the red-eyed damselfly use them as perches and for laying eggs.
• Fish shelter under the leaf cover from sun and herons.

Yellow water lily: where does it grow best?

• Sun or partial shade; it still flowers in partial shade, where a water lily does little.
• Deep water zone: plant at 50–200 cm, measured from the top of the soil to the water surface.
• Only for large ponds and wildlife ponds: allow at least 2 m² per plant.
• Heavy loam or clay; acid to lime-rich water, still or gently flowing.
• Do not let it cover more than half of the water, or the oxygenators will get too little light.

Light

Sun and partial shade

Soil type

Loam, clay or peat

Acidity

Not fussy

Moisture

Wet

Size

0.15 m tall, 2 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Spiked water-milfoil: An oxygenator under the leaf cover, for clear water.
• Yellow flag iris: Yellow flowers at the edge, in harmony with the yellow globes.
• Flowering rush: Pink flower heads in the shallow zone.
• Arrowhead: Arrow-shaped leaves and white flowers in shallow water.

Yellow water lily: when and how to plant it?

Plant in May–June.

1. Plant in May or June, once the water has warmed up.
2. Use a large, sturdy aquatic basket at least 40 cm across with heavy clay or loam, without potting compost or fertiliser.
3. Lay the rhizome at an angle or horizontally, about 5 cm deep, with the growing tip clear of the soil.
4. Top with a 2–3 cm layer of gravel so the soil does not wash out and fish do not dig.
5. Stand the basket at 20–30 cm deep at first, then lower it over a few weeks to 50–200 cm as the leaf stalks lengthen.
6. In a wildlife pond with a muddy bottom you can plant the rhizome directly into the bed, but it will then spread freely.

Care

Feeding

Not needed: it is vigorous enough already.

Yellow leaves

In August and September, cut yellow and dying leaves off as low as possible so they do not rot in the water.

Spent flowers

Remove them if you do not want seedlings.

Cover

Remove leaves or pieces of rhizome if it covers more than half of the surface.

Repotting

Every three to five years in May, lift the basket, trim or divide the rhizome and replant in fresh soil.

Tip: Do not sink the basket to full depth in one go: start at 20–30 cm and lower it once the leaves reach the surface.

Yellow water lily: when to prune it?

Pruning months: August–September.

When: It is not really pruned. In August and September, cut off yellow leaves and spent flowers.

How:

• Cut yellow leaves with long-handled shears or a pruning knife as close to the rhizome as possible.
• Remove spent flower stalks if you do not want seedlings.
• In August, cut off rhizomes growing over the rim of the basket.
• Leave cut leaves on the bank for a while so small creatures can return to the pond.

Caution: Never work alone in deep water, and use long-handled tools from the bank or a sturdy plank.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Division

In May, cut off a 15–20 cm piece of rhizome with a growing tip and a few leaves and plant it in a new basket.

Self-sown seedlings

Seedlings sometimes appear in a wildlife pond; lift them in spring with a little soil and plant them in a basket.

Yellow water lily: how does it get through the winter?

Hardy to −30 °C.

• Fully hardy, to about −30 °C: the rhizome overwinters deep in the mud.
• The floating leaves die back in autumn; the underwater leaves often last all winter.
• No protection needed as long as the basket sits below the ice; at 50 cm or deeper that is always the case in Belgium.

Diseases and pests

• Water lily beetle: Small brown beetles and black larvae eat the leaves, leaving grooves and holes. Hose them into the water, where fish eat them, and cut off badly affected leaves.
• Water lily aphid: Small dark aphids on leaves and flowers. Hose them into the water.
• Brown china-mark moth: Oval holes in the leaves from caterpillars that wrap themselves in pieces of leaf. Remove the loose leaf pieces with the caterpillars underneath.
• Spreading: In a pond that is too small it soon covers the whole surface. Choose a pygmy water lily there instead.

Through the year

• April: New leaves develop underwater.
• May: Plant, repot or divide. Lower the basket gradually.
• June: Flowering begins. Last month for planting.
• July: In flower. Watch for water lily beetle and aphids.
• August: Last flowers. Cut off yellow leaves and spent flowers. Trim rhizomes outside the basket.
• September: Cut off yellow leaves.
• October: Net fallen leaves out of the pond.
• December: Resting: the rhizome lies deep in the mud.

Did you know?

• The showy yellow ‘petals’ are actually sepals; the true petals are small and carry nectar.
• In English it is also called brandy-bottle, after its flask-shaped fruit and the scent of its flowers, which is reminiscent of alcohol.
• The water lily family is among the oldest groups of flowering plants still alive today.