The giant water lily in the Botanical Garden of TU Braunschweig A crowd puller: Victoria nights on August 12 and 13

On August 12 and 13, the Botanical Garden of TU Braunschweig will be open until late at night for a special occasion: the flowering of the giant water lily (Victoria cruziana). The exact flowering dates can only be estimated and announced approximately five days in advance. The Botanical Garden of TU Braunschweig is one of the most beautiful botanical gardens in Germany. It is the ‘green jewel’ of the university and, with over 4,000 plant species, is also a research laboratory, educational, cultural and recreational space.

The giant water lily blooms for only two evenings. On the first evening, it blooms with large, fragrant white flowers, and on the second evening, it blooms with delicate pink flowers. After that, the flower sinks below the water. Image credit: Michael Kraft/TU Braunschweig

One of the biggest attractions for the public is undoubtedly the Victoria greenhouse, where the biggest attraction of our Botanical Garden – the tropical giant water lily (Victoria cruziana) – is cultivated.On 12 and 13 August, the Botanical Garden will be open until 10 p.m. on two consecutive evenings. The reason for this is the night-time flowering of what is probably the most impressive plant in the garden, the tropical giant water lily.

Botanical mythical creature

Until late in the evening, visitors crowded around the water basin in the Victoria greenhouse to see the giant water lily bloom. Image credit: Marisol Glasserman/TU Braunschweig

The Victoria, named in honour of the young Queen of England, was discovered in 1801 by the German botanist Thaddaeus Haenke in the lagoons of a tributary of the Amazon. His reports about this giant ‘botanical mythical creature’ were long doubted.

It was not until decades later that they were confirmed by other researchers. In 1846, the first seeds germinated in London’s Kew Gardens. Three years later, in November 1849, the first flower of this giant water lily opened on European soil.

Giant leaves with extraordinary load-bearing capacity

This perennial plant is grown from seed in the Botanical Garden of TU Braunschweig. In the tropical water plant house, it reaches enormous dimensions in a vegetation period of seven months. The species Victoria cruziana is native to the Paraná River basin and Paraguay. During the summer months, the plant develops shield-shaped giant leaves with a cake tin-like curved edge and a diameter of up to two metres. The large leaf surface has a plastic, air-filled skeleton on the underside, which can be compared to struts and gives the leaf its load-bearing capacity. When evenly loaded, a single leaf can support a child weighing up to 35 kilograms.

Fully developed, the large, fragrant, white flowers with multiple rays open on July and August evenings and close the following morning. The process repeats itself in the late afternoon of the second day. Now the flowers open with a pinkish-red colour. Only then do they finally submerge under water, where the seeds ripen.

Insects for pollination under water

In terms of pollination biology, this is a highly exciting process. In the natural environment, insects bring pollen from outside and pollinate the female parts of the flowers. To do this, they are enclosed in the flowers – in other words, they submerge with the flower for a day. During this time, the pollen matures and is transferred to the enclosed insects. On the second night, when the now coloured flowers open, the insects are released and quickly rush to the next – white – flower. The colour of the flower is therefore a clear signal for the insects.

The pea-like, dark brown seeds are collected by the indigenous population in their homeland as ‘water corn’ and processed into flour.

The Victoria can be seen in the Botanical Garden of TU Braunschweig until mid-September, as after this time the natural length of the day is no longer sufficient for the growth of this ‘botanical mythical creature’.

Author: Michael Kraft, Director of the Botanical Garden