That is certainly the case with the Nymphaea thermarum.

The Nymphaea thermarum was the garden's pin-up for International Day for Biodiversity, in May 2010.

As well as being hard to get at, the Nymphaea thermarum were not flowering in January.

We encamped at a fine Nymphaea lagoon, in the rich shade of a white drooping gum tree.

What you cannot have. The first batch of Nymphaea thermarum seeds arrived at Kew in July 2009.