Gardening: How to grow and care for water lilies

Expert Gemma Neech offers a guide to growing water lilies and types to look out for

Water lilies like to grow in relatively still water in full sun

ASK many gardeners who have ponds which plant they enjoy most, and they are likely to extol the virtues of the water lily, with its stunning flowers and huge palmate leaves.

What's more, there are so many types for virtually every size of water feature, from an old wooden barrel to a huge pond. The beautiful flowers bloom from early summer until September, and many of them have a light fragrance. What they all need, though, is sun.

Gemma Neech, formal ornamental team leader at RHS Garden Wisley, offers a guide to these glorious water-loving plants...

Conditions they need: Water lilies are rhizomatous aquatic perennials that like to grow in relatively still water in full sun, flowering in summer. In the wild, water lilies can be found growing in both tropical and temperate climates. They have leaves varying in size, from small to gigantic, up to 3m in diameter – these giants (Victoria Amazonica) grow in the tropics and are not hardy in the UK, but they are very impressive.

Choosing and buying: If growing water lilies in the UK, it is best to choose a hardy cultivar from a specialist aquatic supplier, and choose a cultivar suited to the size of your pond or lake, as some are more vigorous than others. The best time to buy and plant is late winter or early spring, around February or March. As with buying any plant, make sure water lilies have a healthy crown and there are signs of new shoots and leaves emerging.

Maintenance and care: They can be grown in pots or planted. If grown in pots they will require dividing and feeding to boost growth and flowering, and it is good to do this every two to three years. The ideal time to divide water lilies is in February or March whilst they are dormant. A sharp old bread knife is a good tool for cutting through the rhizomes when dividing water lilies, but no specialist tools are required. When dividing, look out for healthy white roots – if you see black roots, they will be dead. Select firm rhizomes, not soft ones, which are likely to have rotted.

Pests, diseases and other problems: The main pest we find on water lilies at Wisley is the water lily beetle. Its larvae are small and black, eating through the leaves in the summer. The result is a patchwork of elongated holes in the leaves. The only thing that can be done is to hose them off with a jet of water.

Hardy types to consider: Nymphaea 'Gladstoniana': A vigorous aquatic perennial with large, rounded, dark bronze-tinged leaves and star-shaped creamy-white flowers 17-20cm wide, with prominent yellow stamens.

Nymphaea 'James Brydon': Rounded, dark purple-blotched, bronze-green leaves and cupped, carmine-red flowers 12cm in width, with orange stamens.

Nymphaea 'Escarboucle': Round, floating leaves 20-25cm in width, and fragrant, cupped orange-red flowers to 20cm across, with orange stamens.

Nymphaea 'Gonnere': A compact aquatic perennial with bronze-tinged young leaves and globose, scented white flowers 15cm in width, with light yellow stamens.

Nymphaea 'Pygmaea Helvola': A miniature water lily with dark, purple-blotched, rounded floating leaves to 12cm in length, and cupped, fragrant, sulphur-yellow flowers 5cm across, with orange stamens.

Nymphaea 'Marliacea Chromatella': Purple-marbled floating leaves 15-20cm wide, and cupped light yellow flowers 15cm across, with orange stamens.

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