A dwarf with a great story  

This dwarf species of water lily was known only from a single small location in southern Rwanda, near the borders with Burundi and the Democratic Republic of Congo. It grew in a small wetland (20 to 30 meters in diameter) next to the Bugarama hot springs, known by the indigenous name Amashyuza.  
The water lily was discovered in 1987 by the German botanist Eberhard Fischer from the University of Koblenz-Landau. On a subsequent visit to the site, he realized the delicate balance of the habitat and sent several specimens to the botanical garden in Bonn. The plants had been growing there for many years, but their reproduction was not successful.  

At the beginning of the new millennium, a number of factors led to the drying up of the thermal pond, and in 2008 the water lily was declared extinct. The last growing specimens in Bonn provided seedlings that were given as part of an exchange program to Carlos Magdalena Rodriguez at the Royal Botanic Gardens, Kew. He discovered that this water lily does not thrive underwater, but must be grown just below the surface. Subsequently, he managed to grow 30 young plants and the species was saved from total extinction. Over the last 10 years, this tiny water lily has spread to botanical gardens all over the world. In the Czech Republic, it was first grown in our botanical garden but now other Czech gardens participate as well (gardens in Liberec, Pilsen, and Třeboň).  

"Botanical gardens have a crucial role - the conservation of the plant gene pool. It is both the preservation of plants that are rare and endangered and also the gene pool maintenance of species that no longer occur in nature. An example is the Nymphaea thermarum culture in our garden. We have been growing it since October 2018 and it has since flowered regularly in the growing facilities. We have decided to show these specimens to visitors as well," says Vlastik Rybka, deputy of the science department. 

The world's smallest and rarest water lily  

Nymphaea thermarum belongs to the Nymphaeaceae (water lilies) family. The plant is miniature - a single plant is up to 25 centimeters in diameter and a single adult leaf usually measures three to four centimeters. In contrast, the leaf of the largest water lily in the world, Victoria amazonica, can reach up to three meters in diameter.

N. thermarum originally grew in a hot thermal spring, in wet mud. It has tiny white-yellow flowers that open in the morning and close during the afternoon. 

It can bloom at any time of the year.

Time-lapse video of a flowering Nymphaea thermarum water lily

Every leaf is different - an interesting fact, from the life of a dwarf  

Water lilies can have up to three types of leaves. The most famous ones - floating - probably don't need much introduction, because everyone has seen them at some point. These leaves that float on the surface are scientifically called "natant" leaves, but they are not the first leaves a water lily will produce. When a tiny water lily seedling germinates, the first to grow is the (false) natal leaf. It doesn't have a blade yet and actually looks like a kind of hair. The next leaves already look like leaves, but do not reach the water's surface. They are much finer than the floating leaves and are often larger. They differ from natant leaves in several ways and are scientifically referred to as submerged leaves. They do not contain aerenchyma in their blades - a spongy tissue that creates air channels and helps aquatic plants float their leaves. They do not have stomata (breathing pores) because gas exchange underwater takes place across the entire surface of the plant's body. These leaves are especially desired in aquarium water lilies, where the abundance of natant leaves would shade the aquarium and prevent light from reaching the other plants in it. 

When the young water lily has several submerged leaves and it has enough strength to reach the surface, the first natant leaf emerges on a long petiole. This leaf will develop near the surface and if the water lily does not lose it, it will start to produce more leaves. These are carried on by the aerenchyma, which is also present in the stem and is involved in the transport of gases through the plant. Natant leaves have slightly tougher skin and tissues to withstand the weather conditions that prevail on the surface, as well as stomata (breathing pores) on the upper side of the leaf, which facilitates gas exchange. 

Some water lilies form a third type of leaf that sticks out above the water surface and is called an emersion leaf. In the Czech Republic, this type of leaf is found only in the yellow water lily (Nuphar lutea). But it can also be found in the smallest water lily in the world, Nymphea thermarum. These leaves tend to be the smallest and they have a hard stem that can keep the leaf blade above the water. Breathing pores (stomata) are present on both sides of the blade, aerenchyma is present and the tissues are even harder and stiffer than in natant leaves. This type of leaf was mostly formed in plants that needed to get above the water surface for various reasons. For example, because there is more room for them, their surface leaves are destroyed by aquatic pests, or because of frequent surface movement. The formation of submerged leaves can also be observed in our native water lilies in spring when they start to sprout underwater leaves from their rhizomes. Only when they have enough of these do they extend their petioles, go to the water surface and start to cover it with natant leaves.  

Take a stroll through the tropical Fata Morgana Greenhouse and let yourself be carried away by the tenderness and beauty of this dwarf hero. We are looking forward to seeing you!