A member of the Araceae, Water Lettuce (Pistia stratiotes) is a problem floating plant of tropical waterways. The native origin and spread of the species is not known but it has been recorded in both the New and Old World tropics since at least the 18th century. The species is fast growing when in warm and well lit conditions and can completely cover stagnant and slow moving waterways blocking light and making navigation by small boats difficult.
The species is curious both for its fleshy leaves and the curious water repellent hairs that have a basal stem then branch out into four slender processes that rejoin at the tip to give a balloon whisk shape. The flowers are tiny, green and nested in the leaf axils where they can be overlooked very easily.
Like Water Hyacinth, the rapid growth of the species and reproduction by fragmentation, typical of many water plants, make this species a problem weed in some areas.
Holm LG, Plucknett DL, Pancho JV, Herberger JP. 1977. The world’s worst weeds: distribution and biology. (Honolulu: University Press of Hawaii).
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