Two years ago, the world's smallest water lily, a plant known as Nymphaea thermarum whose pads reach only one centimeter in diameter, disappeared from its only habitat, a few square meters near a hot spring in Mashyuza, Rwanda. Local agriculture had drained the spring of most of its water, and as a result, the water lily became extinct in the wild.

Luckily, a few samples had been collected 10 years earlier by the man who discovered the species in 1985, botanist Eberhard Fischer of Koblenz-Landau University in Germany. But unfortunately, the tiny plant proved almost impossible to propagate.

Although Fischer managed to keep the original samples alive at the Bonn Botanical Gardens for more than a decade, seedlings barely grew at all and never reached adulthood.

Last July, Fischer transferred a few seeds and seedlings to the Royal Botanical Gardens, Kew, in London. There, after much trial and error, horticulturist Carlos Magdalena made a startling discovery: Nymphaea thermarum does not behave like any other known water lily. All other water-lily species start life as submerged plants until they become large enough to send pads to the surface. That was how Fischer and Magdalena originally tried to grow them.

Magdalena had tried quite a few variations in habitat to try to get the plants to grow. Trials varied the water temperature, the water hardness, pH and depth. No luck.

Then he looked at the original description of the species from when it was discovered. There was the secret: in its natural habitat, Nymphaea thermarum grew in damp mud at a very specific temperature range. Magdalena took that information, planted seeds and seedlings in pots of loam and maintained the water at a consistent level, and kept it all at 25 degrees Celsius. This exposed the plants to greater levels of carbon dioxide and oxygen from the air, and the plants began to flourish. In November, they flowered for the first time.

"Now we have over 30 healthy baby plants growing here at Kew and some are producing seeds," Magdalena said in a prepared statement, "Soon we may have an army of these tiny waterlilies here at Kew. Its future in botanical collections seems secured for the long term."

The plants will be unveiled to the public at a ceremony on Saturday, May 22.

Meanwhile, Fischer has hopes the plant can be reintroduced to its native habitat. According to a Kew spokesperson, the Rwanda Development Board's conservation and tourism office would like to see Nymphaea thermarum back in the wild, and if different waters are tapped for agriculture, the area where it once grew is fully restorable with little investment.

"When I visited Kew earlier this year I couldn't believe that Nymphaea thermarum, which we thought had gone extinct about two years ago, was thriving," said Fischer in a prepared statement. "These 30 plants were the last viable population of this species on the planet and thanks to the work done at Kew we have an opportunity to secure the future of this fascinating, little waterlily."

Photo: Nymphaea thermarum, courtesy of Kew Gardens