Nymphaea thermarum, also known as the Pygmy Rwandan water lily, is the smallest species of water lily in the world. These tiny water lilies are one of the rarest plants in our Conservatory’s collection. Its pads, which can be as small as 1 cm in diameter, grow in small clusters. Its flowers are also petite, with white blooms that only grow up to 2 cm. Opening in the morning and closing in the afternoon, these flowers have the ability to self-pollinate. Once the plant bears fruit, its stalk bends over to touch the ground, thus releasing its seeds to reproduce.
This water lily species is a critically endangered plant native to southwest Rwanda, where it was discovered growing in the mud along the banks of a hot spring. As farmers started to use the hot spring as a water source, the water lily’s habitat dried up, causing people to believe the species had gone extinct in the wild forever.
In hopes of preserving the species, horticulturalists in Europe rushed to find a way to propagate the plant from seed samples, especially after a rat ate the last remaining Nymphaea thermarum plant growing in Germany. Thankfully, the Royal Botanic Gardens, Kew in England were successful in nurturing their Nymphaea thermarum seeds by growing them in warm, carbon dioxide-rich conditions similar to the plant’s natural environment. Now, the UC Davis Botanical Conservatory is also home to its very own Nymphaea thermarum plant. We were able to obtain this unique water lily from the Missouri Botanical Garden after it was requested by a student. Funnily enough, rats have also tried taking a bite out of our Nymphaea thermarum, which is why you’ll find the plant in a cage if you visit our Conservatory.