Detectives have launched an appeal for information in a bid to help them retrieve the Nymphaea thermarum.
It was stolen from a pond in the Princess of Wales Conservatory after thieves struck between 8.30am and 2.55pm on January 9.
The plant – the leaves of which can be as small as 0.4 inches in diameter, making it the world’s smallest waterlily – was first discovered near a hot spring in Rwanda in 1987.
It is thought its disappearance from the area a couple of years ago was due to the spring, which kept the plants moist and at a constant temperature, being over-exploited.
Kew has more than 50 of the waterlilies and is the only place in the world where they are regularly propagated in large numbers.
Anyone with information about the theft should call Scotland Yard on 020 8721 5934.
Richard Barley, director of horticulture at Kew Gardens, said: “Our staff are dedicated to the conservation of plants and when incidents of this nature occur, it is a blow to morale.
“We take theft of our invaluable scientific collection of plants very seriously and this matter is with the Metropolitan Police.”
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