Family: Nymphaceae
Common Name: Water Lily

Water lilies are without doubt the best known and most widely grown of all aquatic plants. Species occur naturally throughout the world, both in tropical and cold regions, but many more hybrids than species are in general cultivation. They are broadly classified as either hardy (cold tolerant) or tropical. The two groups do not cross pollinate so they cannot be interbred for colour. Most hardy varieties are day blooming, as are many tropicals, but some tropicals also flower at night.

Water lilies have a glorious colour range, including white, cream, yellow, orange, pink, rich crimson, blue and purple. Tropical varieties include blues and purples not found naturally amongst the cold-tolerant types. Many water lilies have plain, dark green leaves, but a great number have leaves that are heavily splashed or Notched in deep maroon or purple. In cool and cold climates, hardy water lilies flower in summer and sometimes into autumn. Tropical varieties will not come into bloom before summer, except in the true tropics. In cool regions, flowering usually commences in late spring or early summer and continues through summer. All water lily blooms make beautiful cut flowers.

Water lilies are grown worldwide, in small ponds and large ornamental lakes, from the tropics to the cool zones. Water lily pools have been enjoyed for centuries in Arabic and Moorish gardens, and also by the Chinese and Japanese, but they did not become popular in Europe until the late 19th century. At this time, wealthy collectors built heated glasshouses containing pools in which a range of tropical water lilies was grown. Prior to this, the only variety that could be grown outdoors in cool to cold climates was the white Nyanphaea alba. Water lilies were immortalized by the French Impres­sionist painter, Claude Monet, in a series of large-scale paintings done in his own garden at Giverny in France. Today, these gardens are visited by thousands of people every year.

Species

N. alba, zone 5, from Eurasia, has dark green leaves, crimson beneath, and slightly scented, white flowers.

N. caerulea, zone 10, the so-called blue lotus, from tropical and North Africa, has star-shaped, pale blue flowers.

N. capensis, the Cape water lily, zone 10, has very fragrant blue flowers.

N. gigantea, the Australian water lily, zone 10, which is native to tropical Australia and New Guinea, has very large leaves, up to 50 cm (20 in) across, and large, blue to purple flowers. It spreads up to 3 m (10 ft) in tropical waters.

N. odorata, zone 3, a fragrant American species with white flowers, is being used today in hybridizing work, as is the dwarf species, N. tetragona, which is suited to zone 2. Small forms are becoming increasingly popular because they are well suited to growing in small ponds with shallow water. Few straight species of water lily are grown today, except by specialist growers and collectors. This is due to the vast range of beautiful hybrids available. Home gardeners should visit specialist growers to see what is available and to seek advice on their culture.

Cultivation

Water lilies thrive and flower profusely only in full sun. Most will grow in water 30-50 cm (12-20 in) deep, although true miniatures prefer water of only 10-15 cm (4-6 in) depth. In the tropics, very vigorous types can be grown in water 1-2 m (3-6 ft) deep. In cool regions, there must be sufficient depth of water above the crown of the hardy water lilies to prevent them from freezing.

All water lilies like to be grown in still water, away from fountains, pumps and cascades. They are usually potted in a mix of three parts of good quality soil to one part of very well decayed cow manure. After potting, the top of the soil should be covered with a layer of gravel or pebbles.

Potted plants should be lowered into the pond very gently and slowly in order to avoid dislodging the plants or the mix. Propagate by lifting and dividing the rhizomes and removing offsets in late winter or early spring, depending on the district. In frost-prone climates, tropical water lilies need to be grown in a pool in a heated greenhouse or conservatory, with a minimum winter temperature of 10°C (50°F).

Climate

There is a water lily to suit every climatic zone, but advice should be sought from an expert grower to ensure that the right choice is made.