Kew Gardens Waterlily House

This small, elegant glasshouse is another of Kew’s classic listed buildings. Located opposite the northern entrance of thePalm House, its square glazed structure encloses a circular pond spanning 36 feet. It was completed in 1852 specifically to showcase the giant Amazon waterlily (now called Victoria amazonica), which had first been encountered by European botanists in South America at the beginning of the 19th century. Victoria amazonica is well known for its huge circular leaves, which are often pictured with a small child sitting supported in the centre as a demonstration of their size and strength. The species is highly prized as an ornamental, despite having somewhat particular requirements for successful cultivation. Native to tropical South America, Victoria amazonica was first discovered in Bolivia in 1801 and named Eurgale amazonica. It was subsequently moved to a new genus named in honour of Queen Victoria (originally as Victoria regia). In South America it grows in the backwaters of rivers in the Amazon basin, the Guianas and the Pantanal. The enormous circular leaves, which grow to over 2.5 m across, have upturned rims and are anchored by long stalks arising from an underground stem buried in the mud of the river bottom. The leaves first appear as spiny heads but expand rapidly up to half a square metre per day. The upper surface has a rather quilted appearance and a waxy layer that repels water. The purplish red undersurface has a network of ribs clad in abundant sharp spines, possibly a defence against herbivorous fishes and manatees. Air trapped in the spaces between the ribs enables the leaves to float. They are so buoyant that they can easily support the weight of a small child, and a mature leaf can support 45 kg if the load is evenly distributed. In a single season, each plant produces some 40 to 50 leaves, which cover the water surface and exclude light, thus restricting the growth of most other plants. The spectacular flowers are relatively short-lived, lasting only 48 hours or so. The flower is white the first evening it opens, attracting beetles with a sweet pineapple-like scent and with heat from a thermochemical reaction. At this stage the flower is female, and is open to receiving pollen picked up by the beetles on other plants. As they bumble around inside the flower they transfer pollen to the stigmas and fertilization takes place. Meanwhile the flower shuts, trapping them until the next evening. During the following day the plant changes from female to male: the anthers mature and start producing pollen. When the flower reopens on the second evening it has changed colour to purplish red and no longer emits attractive scent or heat. The beetles, dusted with their pollen, fly off to find another white flower on a different plant (each plant only ever has one white flower at a time), where the process is repeated. The flower then closes up and sinks below the surface of the water, its mission accomplished. Although not currently thought to be threatened, this plant lives in a highly specialised habitat. Climate change predictions for the Amazon basin are severe, and rainforest destruction, with consequent impacts on water quality and flow, may pose a significant threat in the future. Plants are grown in the Tropical Nursery, which is one of the behind-the-scenes areas of Kew. In March or April, when the plants have 5 or 6 leaves, the best specimens are moved out, so during the summer months you may be fortunate to see them growing in the Princess of Wales Conservatory and/or the Waterlily House.