Water lilies make a splash

RECENTLY I’ve spent quite a bit of time travelling in my boat on the Shannon and its tributary, the Suck. The pleasure of travelling our inland waterways in summer is added to by the fact that the water lilies are in flower.

There are two native species in Ireland — the yellow water lily and the white water lily. There are also some exotic species and cultivated varieties that have escaped and established themselves in the wild, mostly in ponds on old estates. One of these species, the fringed water lily, has been officially classified as an invasive alien plant.

The two native species are easy to tell apart when they’re in flower because, as you might expect, the yellow water lily has yellow flowers and the white water lily has white ones with yellow stamens and often a faint pink flush on the petals.

The yellow ones are commoner and the white ones, which prefer slightly deeper and more acid water, are largely confined to the west and south. The rivers I was travelling were in the middle of the country and, in a few places, I spotted the two species flowering together. The flowers of the white water lily float on the surface, in typical water lily fashion, and they open in the morning and close in the late afternoon.

Later in the summer the flower stem retracts and the seed capsule ripens under water and then bursts to distribute the seeds. The leaves, or lily pads, are rounder than in the yellow water lily. White water lilies are the ancestors of most temperate cultivated varieties. They prefer to grow in water over two metres deep, yellow ones will grow in a metre and a half.

In the late autumn the plant dies back and over-winters as a large root or rhizome in the muddy bed of the river, lake or canal. The severe winter of 2010 and 2011 killed a lot of these rhizomes, particularly those of the yellow water lily in the Midlands and east of the country, but they are making a good come-back thanks to milder winters since.

The yellow water lily has more heart-shaped leaves and the golf ball sized yellow flower is rounder and held on a stalk several centimetres above the water surface. The seed capsule ripens above water and is bottle shaped. The species is sometimes called the brandy bottle, which may be because the flowers have a strong alcoholic scent, different to that of the more fragrant white water lily, to attract pollinating insects.

There is some archaeological evidence to suggest that water lily seeds were an important component of the diet of our fisher-gatherer and crannóg dwelling ancestors in prehistoric times.