Why British ponds love a water lily

Few sights say summer pond quite like a water lily opening its petals to the sun. Beyond their beauty, these floating favourites earn their place in any British wetland garden. Their broad leaves shade the water, which helps keep blanketweed and green algae in check. That shade also gives frogs, newts and small fish a place to hide, while the flowers offer nectar and pollen to bees, hoverflies and other pollinators. Dragonflies and damselflies often use the leaves as resting platforms, and the underwater stems provide cover for tadpoles and aquatic invertebrates.

Hardy water lilies are the mainstay for UK ponds. They die back in autumn and return reliably each spring, unlike tropical types that need lifting and frost-free winter storage. If you have a small container pond, a half-barrel or even a generous sink, there is a lily to suit. The trick is choosing one that matches your water depth and giving it the right start.

Match the lily to your pond depth

Water depth is the single most important factor. Measure the distance from the surface to the top of the planting basket, not to the bottom of the pond. A lily planted too deep will sulk and may never flower. One planted too shallow can push leaves above the water, where they scorch and curl. As a rough guide, hardy lilies fall into three practical groups.

• Pygmy and small lilies: happiest in 15–30cm of water. Ideal for tubs, half-barrels and shallow wildlife ponds. Look for compact cultivars with small leaves and frequent, modest flowers.
• Medium lilies: suit 30–60cm of water. This is the classic garden pond range and offers the widest choice of colours, from white and yellow to pink, red and copper.
• Large lilies: need 60–120cm or more. These include the native white water lily, Nymphaea alba, and the vigorous yellow water lily, Nuphar lutea. They are magnificent in big ponds and lakes but will overwhelm a small garden pond.

If you are unsure, choose a smaller lily rather than a larger one. Water lilies actually flower best when slightly pot-bound, and a modest plant in a small pond looks far better than a monster crowding every inch of surface. Aim to cover no more than a third to a half of the water with leaves, leaving open water for wildlife and for viewing.

Planting a water lily correctly

Late spring to early summer is the best time to plant, when the water has warmed and new growth is underway. Use a purpose-made aquatic basket, which has open sides for roots but holds the compost together. Line it with hessian if the mesh is large, then fill with aquatic compost or a heavy, loam-based soil. Do not use ordinary multipurpose compost, which is too light and will float away, and avoid anything rich in peat or bark.

• Trim any damaged or excessively long roots, but keep healthy white roots intact.
• Position the rhizome so the crown sits just at the surface of the compost, not buried.
• Firm the soil gently around the roots, then top with a 2–3cm layer of pea gravel or washed stones.
• Soak the basket in a bucket of pond water until bubbles stop rising.
• Lower it into the pond on bricks or blocks to the correct depth for the cultivar.
• Remove the bricks gradually as the leaves grow and reach the surface.

Choose a spot in full sun for at least six hours a day. Still water is fine, but avoid placing the basket directly under a fountain or in a strong current. If your pond has koi or other large fish, protect the young plant with a temporary cage of netting until it establishes.

Feeding and summer care

Water lilies are hungry plants, but they need the right kind of food. From late spring to late summer, push specialist aquatic fertiliser tablets into the compost around the roots, following the packet rate. A typical schedule is every four to six weeks. Never use general garden fertiliser, which dissolves into the water and feeds algae instead of your lily.

Keep the pond tidy by removing yellowing leaves and faded flowers. Deadheading encourages more blooms, though leaving a few seed heads can benefit wildlife. If aphids cluster on stems or buds, a sharp spray of water from a hose will dislodge them without harming pond life. Thin overcrowded leaves if they cover more than half the surface. In a warm summer, you may need to lift the basket slightly if leaves start to push above the water line.

Dividing and repotting overgrown lilies

Every three to five years, or when flowers become small and sparse, it is time to divide. Lift the basket in early spring, just as new shoots appear. Use a sharp knife or secateurs to cut the thick rhizome into sections, making sure each piece has at least one growing point and a good set of roots. Discard the old, woody centre.

Repot the divisions into fresh aquatic compost and top with gravel as before. Replant at the correct depth for the cultivar. Dividing not only rejuvenates the lily but also gives you spare plants for another pond or to swap with a gardening friend. Any surplus can be left in a shallow tray of water in the shade until you find a home for it.

Wildlife, pests and winter

A well-grown water lily is a wildlife hub. Frogs bask on the leaves, newts shelter beneath them, and emerging adults of damselflies and dragonflies climb the stems to dry their wings. Leave a few leaves and seed heads in place over autumn for insects and birds. The main pests are aphids and the larvae of the china mark moth, which cut small pieces from leaves. Pick off affected foliage and encourage birds and frogs to patrol the pond naturally.

Hardy water lilies need little winter care in most of the UK. As foliage dies back, cut it away and leave the basket in place at the bottom of the pond. In a severe winter, avoid smashing ice, which can shock fish and damage pond liners; instead, place a pan of hot water on the surface to melt a hole. Tropical lilies must be lifted before the first frost and kept in wet compost in a frost-free place. In spring, clear debris, check the basket depth, and start feeding when the first new leaves appear. With that simple rhythm, your water lilies will reward you with flowers for years to come.