Geography and distribution
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.
Threats and conservation
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.
It is said that the complex 'architectural' pattern of the vein structure below the leaves provided the inspiration for Joseph Paxton's Crystal Palace design in 1851, for the Great Exhibition in London. However,
Victoria amazonica is most valued as an ornamental plant, for which it has been highly prized ever since its discovery. The seeds of this species can be roasted and eaten.
In the wild the giant waterlily is a short-lived perennial, but at Kew it is raised as an annual from seed planted each January.
In summer the flowers are hand-pollinated and then placed in a bag. This enables easy collection of the resulting seed, in the autumn. The seeds must be kept moist, preferably in water, all the time. To prevent premature germination, or death, they are kept at a constant temperature of 15 °C. In order to begin germination it is sometimes necessary to nick the seed with a scalpel, after which germination occurs in ten days. In January the newly germinated seed is pricked out into a tiny pot which is kept in water. As the plant grows, potting on into larger pots is carried out until the plant occupies a one ton pot. Loam is used as a substrate, the key factors for this choice being that it does not float, it is rich in nutrients and it has the capacity to enclose the fertiliser that is contained in the ‘feed bombs’ given to the plant.
Carlos Magdalena, who cultivates this species at Kew, notes that temperature and light are crucial. The seedlings are raised at 32 °C and the juvenile and adult plants are grown on at 26 to 32 °C. In the winter, supplementary lighting must be provided for the seedlings. A 400 watt horticultural supplementary bulb is used to give bright light for 12 hours. The brighter and longer the exposure to light, the better and faster the plant grows. Eventually, in autumn, it is the lack of light that finally causes the plant to die.
Pests and diseases are kept at bay with the provision of plenty of rich fertiliser, but aphids can be a problem.
If the plant becomes pot-bound, the crown tends to lift until it is raised out of the water. To counter this, the ‘chop and drop’ technique can be used whereby the crown is cut and planted in a new pot. Alternatively the pot can be placed deeper in the water. The general rule is: the larger the pot, the larger and healthier the plant.
General maintenance includes weekly feeding throughout the season using 'feed bombs' and prompt removal of decaying leaves. The pot in which the plant is growing is kept submerged in water at all times.
Giant waterlily at Kew
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.
The species normally grown at Kew are
Victoria amazonica and V.cruziana, and their hybrid, V.‘Longwood’. The giant waterlily that is seasonally on display in the Princess of Wales Conservatory is normally V.'Longwood'. In 1995 the leaves reached record-breaking dimensions when they grew to over 2.5 m in diameter and were registered in the Guinness Book of Records. V.cruziana is normally grown in the Waterlily House.
Kew also raises juvenile
Victoria plants to donate to other institutions that do not have facilities to raise them from seed.