Waterlilies

Instantly recognisable, waterlilies are possibly the most sought after of all waterplants. Choose from many elegant flower shapes and colours with attractive, lush foliage. With dwarf and large forms available, they are an excellent choice for a half wooden barrel, informal pond or the largest formal pool.

Waterlilies (Nymphaea)

Quick facts

Common name Waterlily
Botanical name Nymphaea
Group Aquatic perennial
Flowering time Summer
Planting time Later spring to summer
Spread Dwarf species 30-60cm (1-2ft); small/medium 60cm-1.5m (2-5ft); vigorous 1.5-2.4m (5-8ft)
Aspect Full sun
Hardiness Fully hardy to frost tender
Difficulty Moderate to difficult

Cultivation notes

Choosing waterlilies to buy

  • Look for a healthy crown and make certain that there is no damage to the buds or leaves
  • Ensure the nursery display tanks are not weed-infested as you could transmit problems to your pond
  • Waterlilies vary widely in vigour. Make sure the ultimate plant size is suited to the pond and depth of water available
  • Small cultivars can be accommodated in large ponds by using bricks to raise them up to the correct level but overly vigorous plants may take over smaller ponds

Planting waterlilies

To grow successfully they need calm, still water away from disturbance by waterfalls, fountains or pumps. They are best planted between late spring and late summer in an open position with full sun.

  • Waterlilies are best grown in aquatic baskets. Choose a suitable size for the plant’s vigour
  • Line the basket with hessian and fill with loamy soil or aquatic plant compost, planting the crown at soil level
  • Trim back any long roots and cut off old or damaged leaves and flower buds
  • Water well before placing in the pond, then submerge the plant so that 15-25cm (6-10in) of water covers the crown and young leaves float on the surface
  • To ensure the correct depth place the basket on bricks or other raised platform. In a new pond the basket may be positioned on the bottom before the pond is filled
  • As plants grow, gradually lower the container in stages until it finally rests on the bottom of the pond
  • Tropical waterlilies can be planted at their permanent depth immediately as they grow quickly

Feeding

Waterlilies are heavy feeders and benefit from a proprietary aquatic slow release fertilizer added into the compost or soil during the growing season, following the manufacturer’s instructions.

Maintenance

Flowers last three or four days and should be cut off below the water line along with any old leaves before they sink and rot.

Propagation

Division: Rhizomatous waterlilies can be divided every four to five years depending on the vigour of the plant. To maintain vigour, divide waterlilies when they are overgrown and congested, with few flowers or when the roots have outgrown the container. Leaves pushed out of the water rather than laying flat on surface can be another sign that it is time to divide.

  1. Lift the plant in late spring or early summer
  2. Remove small rhizomes (about 15cm (6in) in size and each with a young shoot) from the thick main crown using a sharp knife
  3. Pot up the rhizomes into a loamy soil (mixes are sold at aquatic centres) and firm well
  4. Insert the new offshoot into aquatic baskets just under the soil surface with the fibrous roots spread out below and top the soil with a layer of washed pea shingle

Bud cuttings: Some tuberous waterlilies can be propagated by bud cuttings. They produce sideshoots or eyes which can be cut from the roots. Press each cutting into a prepared container, top-dress and immerse in water in a greenhouse at 15-18°C (59-64°F). As plants grow, pot them on, increasing the water depth until they are ready to plant out in the pond the following spring.

Separating root buds or plantlets in spring or early summer: Some tropical waterlilies produce young plants that may form and bloom while still attached to the parent leaf. Transplant into shallow pans in water and grown on at 15-18°C (59-64°F). Gradually increase the water level then pot up into aquatic containers.

Seed: Some hardy waterlilies do not readily set seed but tender or tropical species set large quantities and may be grown from seed. Sow hardy seed immediately, if available, before it dries out. Tropical waterlily seed is best sown in spring.

  1. Sow seed evenly in pans of seed compost
  2. Sprinkle with compost, water, and then place pans in a container and cover with 2.5-5cm (1-2in) of water
  3. Hardy waterlily seed requires a minimum temperature of 13°C (55°F) to germinate; tropical seed 23-27°C (73-81°F)
  4. When seedlings are large enough to handle, plant in pans submerged in 5-7.5cm (2-3in) of water
  5. Pot on later into 6cm (2.5in) containers in 8-10cm (3-4in) of water

Cultivar Selection

Hardy cultivar selection

The smaller cultivars and dwarf waterlilies, suit half barrel or mini pond and water 30-45cm (1ft-18in) deep:

N. ‘Pygmaea Helvola’ AGM: Tiny olive-green leaves marked purple-brown spreading 30-45cm (1ft-18in). Free flowering star-shaped blooms of canary-yellow, flowering through summer.

Small to medium waterlilies need a water depth of 45-75cm (18-30in):

N.’James Brydon’ AGM: Good in part shade with purplish leaves spreading 90cm-1.2m (3-4ft) and fragrant free-flowering vivid rose-red flowers, June to September.
N. ‘Paul Hariot’: Has purple mottled leaves spreading to 1.2m (4ft). Sometimes known as a ‘changeable’ waterlily because the free flowering blooms change colour over the season. This particular one changes from creamy-apricot to deep pinkish-orange with age.

The largest waterlilies suit a large pond or lake, with a water depth of 75cm-1.2m (2.5-4ft):

N. ‘Escarboucle’ AGM: This is possibly the best red waterlily. A leaf spread of 1.2-2.5m (4-8ft) and fragrant, free-flowering, rich-red blooms, 30cm (1ft) across produced through summer.
N. ‘Gladstoniana’ AGM: Spreads vigorously with distinctive wavy-edged leaves and white flowers that are up to 30cm (1ft) across.

Links

RHS Plant Finder
RHS Plant Selector
AGM's

Problems

Leaves may protrude above the surface if the water is too shallow or if the plant is congested and needs repotting in a larger basket.

Promptly remove and destroy any leaves with waterlily leaf spot. It appears as reddish or grey-brown concentrically marked spots on both leaf surfaces.

Reduce infestations of the following pests by hosing down foliage with a jet of water, remove the pests by hand or cut out heavily infested leaves. Pesticides must not be used because of the danger to fish, amphibians and other pond wildlife:

  • Waterlily beetle and larvae damage the upper surface of leaves by eating extensive elongated holes
  • Waterlily aphid can infest the foliage and buds, soiling them with cast skins and sooty moulds
  • Larvae of leaf-mining midge can cause extensive damage to waterlily leaves in new or refilled ponds
  • Brown china-mark moth caterpillars make regular rounded-shaped holes in the leaf margins

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