Tropical Waterlilies. 23.07.12

In the last couple of weeks we have visited a couple of gardens that grow tropical waterlilies making a magnificent show. They are spectacular plants that require water temperatures above 20degC to grow and flower. In the UK they can really only be grown in heated greenhouses and they need quite large ponds so they are only grown well in a few collections. One advantage of plants grown in a greenhouse is that it is usually possible to get close to the flowers. The day blooming cultivars will open in mid-morning and close again in late afternoon, for three or four days. The night blooming cultivars are often more strongly scented and open from late afternoon until the middle of the next morning. The leaves are more variable than the hardy waterlilies and may be smooth edged or fluted and mottled or striped in purple and green.

This is 'August Siebert' growing at Wisley. Raised by F.Henkel in 1902, a seedling from N.gracilis pollinated by N. 'Laydeckeri' (an old hybrid of uncertain parentage, described by Vilmorin in 1891). A fragrant day flowering hybrid with rose pink flowers on tall stems. It grows rather large and needs a lot of space eventually - which is the key word - many of these plants are grown as annuals, planted out in areas with reliable summer heat and allowed to die with the first frosts.

'Carlos Magdalena' was raised by Kit Knotts in Florida in 1999. The parents are the white N.ampla and N. 'Pink Perfection'. The lavender blue flowers have a yellow centre. One of the newer varieties grown in the waterlily house at Kew. Kew make full advantage of the limited space available to grow them, and replace the cultivars on show quite frequently so they usually have the best of new varieties on display. They have limited space behind the scenes so there is no room for second rate plants!

This is 'Foxfire', one of my favourite recent hybrids. The leaves are strikingly marked with purple and toothed at the edges. The large pale blue flowers are very striking especially when seen as they are here at Kew, growing in a black pool to enhance the contrast. Raised by J.Craig Presnell in Florida in 2003, the parents were an unnamed seedling pollinated with N.ampla. In this picture the centre of the flower looks white but it is usually pink which gives a great richness to the colour. It was awarded Best Waterlily for 2005, it opens very early in the morning and closes late.

'Midnight' is one of the older purple varieties. It is very floriferous and the stamens are petaloid, enhancing the 'double' effect of the flower. The leaves have irregular corrugations at the margin and are pure green. Raised by George H Pring in 1941, it was one of his later introductions. Pring was born in Devon in 1885 and apprenticed at Kew. When he was 20 he took up a post at Missouri Botanic Gardens where he remained for 63 years. He started crossing tropical waterlilies in 1912.specialising in day blooming cultivars and doing a lot of work with yellows. His hybrids are still the cornerstone of modern waterlily breeding.

This is 'Piyalarp' raised by Dr. Slearmlarp Wasuwat in Thailand, a deep pink cultivar with bronze leaves, introduced in 2007. Photographed at Kew.

'Rhonda Kay' was raised by Ken Landon in Texas and photographed at Kew. This purple blue struck me bacause of the orange yellow centre. A hybrid between N. capensis var zanzibarensis 'Purpurea' and N.flavovirens raised in 1984 and named after his two sisters.

Zanzibar features heavily in the minds of tropical watelily breeders. It was the original source of N.capensis var zanzibarensis which has (in some forms) much darker and richer purple-blue colours than the type. 'Purple Zanzibar' is one of those forms, and provided the pollen for this hybrid, 'Star of Zanzibar'. The seed parent was 'Morning Star'. Raised by Rich Sacher in New Orleans, in 2000 it won Best in Show at the Banksian Trials held by the International Waterlily Society at Chicago Botanic Gardens. Photographed in the RHS gardens, Wisley.

'Texas Shell Pink' is a very beautiful pale cultivar that holds its flowers well above the surface, photographed at Kew. Raised by Rolf Nelson in Texas.

N. x daubenyana photographed in Oxford Botanic Garden. A vigorous hybrid between N.caerulea, the Blue Waterlily of the Nile, and N.micrantha from tropical west Africa. The origin of the hybrid is unknown but N.caerulea has been widely grown in tropical climates for centuries. The hybrid was first described in 1864 in now occasionally found naturalised in the southern states of the USA.

Nymphaea thermarum was discovered by Eberhard Fischer in 1987 growing in the overflow of a hot spring in Rwanda. It was later discovered that this single spring was its only location. It became extinct in the wild in 2008 when local farmers diverted water from the spring for their use. Two plants survived in Bonn Botanic Gardens but they were not able to propagate the species. The problems were solved by Carlos Magdalena working at Kew who managed to germinate seedlings in pots of loam at the water surface, rather than submerged as would be usual for waterlilies. This picture was taken at Kew, where the species is now sufficiently secure to be put on public display. It is a tiny species that may give rise to hybrids that could be cultivated in very small containers, and possibly make tropical waterlilies a more practical proposition even in the UK.