For sure it is not necessary to introduce hardy waterlilies. Everybody knows them – from lakes and ponds or at least from pictures. In many cases the wish to keep waterlilies in the garden was the main reason to construct a pond in the garden.  But you need not necessarily have a pond to grow them. There are small varieties that do well in barrels or tubs. 

Today we can choose from a very large number of waterlily varieties the one that suits us best. There are big and small varieties in a large scale of colours. At the moment there are hardy waterlilies in all colours except blue and violet. In a few years there will be probably also blue and violet ones, for in 2008 a great break through in the hybridisation of waterlilies happened. 

Under the climatic conditions of Central Europe waterlilies are hardy if their roots are not completely enclosed in ice during winter. Even during cold winters the ice crust on lakes and ponds doesn’t become thicker than about 40 cms. It has to be extremely cold for a very long time to cause a solid frozen pond or shallow lake. The artic waterlily Nymphaea tetragona will survive even that, for it occurs naturaly circumpolar and prefers water just 10 – 20 cms deep. 

It is possible to keep waterlilies in half barrels or tubs, but they shouldn’t stay there during winter. Frost will attack those containers not only from above but also from the side and therefore the usualy freeze solid. It is not only the waterlily that will be killed by the ice, also the barrel or tub will be damaged. When water freezes, it extends its volume considerably. The rings of a barrel will burst ant the staves fall apart, with tubs the bottom is often pushed away or the sides simply burst. Therefore it is necessary to empty such containers in autumn and winterize them dry. The waterlily can be transfered into a bucket of water and may spend the winter in a cold almost frost free room (for example a unheated cellar). 

When you choose a waterlily please consider not only the colour but also the growing characteristic of the variety. There are strong growing varieties that can spread all over a pond in no time. Such varieties are easily propagated and hence they are cheap. It is a questionable saving of cost to choose such a cheap variety if the consequence is to jump into the pond every other year and fight the overgrown monster with spade and saw. This is not only really heavy labour it is also a thread to the pond liner. Working hard for hours in the pond just to earn a leaky pond will put you off even the most beautiful waterlily. There are also waterlilies that grow slower or even extremly slow. In most cases they are a better choice for an average pond. Of course these varieties are more expensive since it takes more time to propagate them. Some of them are so hard to propagate they are available only in small numbers. They are worth the money if you consider the damage a strong growing variety can cause. 

Whatever variety you choose, it is advisable to plant it into a planter and not directly into the bottom of the pond. Waterlilies need heavy soils and a lot of fertilizer – both you don’t want in your pond to keep growth of the algae at bay. If you use a planter you need fewer soil for the waterlily and it is possible to fertilize very targeted and exact. That way you feed the waterlily and not the pond water. For most varieties a planter that contains 5 to 10 liters is sufficient. An exception are all Nymphaea odorata hybrids. They need to form a small colony to become floriferous, so they need larger planters like 90 liter tubs. The rim of the tub is cut back so that the tub is just about 20 cms high. It is a wide planter the odoratas need, not a deep one. 

The trade offers plastic baskets that are made especially for waterlilies. In most cases they are too small for waterlilies and their holes cause more damage than benefit. If the holes are ment for better arification – it won’t work under water. Worse is the fact that soil leaks through the holes. Imagine you have just planted your newly aquired waterlily into a basket with holes. When you move the basket through the water to the bottom of the pond, water enters through the holes and a small amount of soil is leaked out. There are many reasons why it may be necessary to lift the basket and transfer it to another place – more often than not simply because you are not pleased with the impression the plant provides at this place. So the basket is moved a second time, perhaps lifted from the water and emerged at another one. Moving the basket up means leaking soil through the holes as well as moving the basket down does. That way you can easily loose about 50 % of the soil in the basket. Evidently the manufacturers of those baskets finally realized this problem for they offer now special liners for their baskets. My, what a clever idea! First we pay extra for holes and then we have to buy a liner to seal them again? 

There is yet one more objection:  plastic baskets break easily. After a few years under water the plastic becomes so brittle, it will break if you ever have to move the basket. 

Fill the planter for the waterlily with heavy soil. Very suitable is the soil that you find directly under the roots of your lawn. If you want to make it even better add some loam. Avoid organic fertilizers and organic components like peat, compost or bark. They will all cause rot and may kill the waterlily. Your waterlily needs fertiliser to produce lots of flowers. The best fertiliser in this case is a slow release mineral fertiliser. Organic fertilisers change the water into liquid fertiliser, cause algal bloom and may even kill the waterlily. The kind of fertiliser we use in the nursery is Osmocote tablets. It retains the nutrients and releases them little by little to the roots of the waterlilies. 

When you plant the waterlily add such slow release fertiliser to the soil (we use two to three tablets per planter and add one more every year) and fill the planter with so much water that the soil is completely soaked before you put the planter into the pond. If is not necessary to repot the waterlily every year but it needs fertiliser every spring. 

The best time to plant waterlilies is in May and June. At that time waterlilies are often sold bare rooted. What you get then is a socalled rhizome. The rhizome is that part of the waterlily that grows horizontally in the soil. To the bottom it sends down roots and to the top it sends up leaves and flowers. It is necessary to plant it horizontally into the soil (there is only one exception: a few waterlilies develope socalled ‘pineapple rhizomes’. The really look like a small pineapple and have to be planted vertically). The point of the rhizome where leaves and flowers come from is called ‘growing tip’ or ‘crown’. It is very important not to cover the crown with earth when planting the waterlily. If the crown is covered, it may start to rot away. 

Waterlily rhizomes do contain air chambers and float in water. Therefore it is necessary to anchor the rhizome well in the soil. The more clay or loam soil contains the more it will be able to hold the rhizome. If this is not sufficient you can lay a flat stone on top of the rhizome to keep it down. After planting is done the surface of the planter is covered with a layer of gravel. It keeps fish from unearthing the rhizome and also works to hold the rhizome down. 

Waterlily nursery usualy grow all varieties in very shallow water (about 30 cms deep). If you put the planter considerably deeper into the pond you cause your waterlily trouble. It is advisable to slowly accustom it to deeper water. You can do it easily with a few bricks. Choose the place where you want the waterlily to be. Pile up there in the pond as many bricks as are necessary that the leaves of the waterlily are barely covered with water when you put the planter onto the pile of bricks. As soon as the waterlily has grown enough to allow the leaves to float on the surface remove one brick. Now the leaves are again under when. As soon as they reach the surface you remove the next brick and so on until the planter stands on the bottom of the pond. This may sound pedestrian, but it pays off. Sadly our summers are short. If the waterlily is planted in deep water at once it may relapse and not recover for several weeks. Weeks the waterlily needs to develope flowers and that are lost without need. 

Waterlilies start blooming around mid May and they end blooming around early September. Yellow varieties start about two weeks later but won’t stop till their buds are killed by the first frost. Each flower has a life span of three days, at most four days. Afterwards it decays and sinks to the bottom of the pond where it either sets seed or simply disolves. In Autum the waterlily stops growth and restricts itself to some submerged leaves. If your pond is very small you can cut back the waterlily at that time. If the leaves disolve in the pond they set free nutrients that are not welcome in the pond at that time of the year. 

Waterlilies are quite sturdy plants. Aphids may apear on the buds but it is a rare case and the aphids can be washed down with a garden hose. China Mark Moth (Elophila nymphaeata) and Waterlily Leaf Beetle (Galerucella nymphaeae) are more serious pests and more difficult to fight. Both won’t kill the waterlily but they cause damage and make it look shabby. Since both pests are able to fly they may appear at your pond if there is an infected pond within a radius of 3 km. 

The China Mark Moth is a small white butterfly (a moth) that lays ist eggs onto the leafs of waterlilies and irises. The caterpillars that develope from the eggs are small but quite voracious. First thing after hatching it cuts off a piece of waterlily leaf and wraps itself into it. The result looks like a tiny cigar and in the protection of this cigar the caterpillar floats along the pond. Where ever it comes in reach of waterlily leaves it will nibble at them. Affected leaves are always damaged from the leaf edge. The best way to fight the China Mark Moth is collect the caterpillars by hand – it takes a sharp eye to do that successfully. The butterfly arrives at the pond in two to three waves during summer. Theoretically it can be controlled by the use of Bacillus thuringensis, but the use of all kinds of pesticides and insecticides in water bodies is not permited – with good reason. 

The Waterlily Leaf Beetle is a small brown beetle and again it is its caterpillar that causes the trouble. The beetle lays its egg case (yellowish-brown squares) on top waterlily leaves and from there the hatched caterpillars start to eat up the leaf. Accefted leaves are often completely perforated by the burrows of the caterpillars. Again the only way to fight the larvae is collecting them by hand. The beetle itself is attracted by white surfaces, so it is possible to catch it with white glue-boards. The beetle appears two times during the season, first time already in May. If all leaves of the waterlily are cut and destroyed at that time, the population of the beetle is remarkably reduced. 

Crown Rot is the most severe disease waterlilies can get. The rhizome of affected plants rots away from the crown (the tip) and is turned into a stinking mass. The waterliy is killed by this disease. It is a fungal infection that traveled from potatoes to waterlilies that were kept semi-aquatic for mass production. So far there exists no cure for it and water from ponds with infected waterlilies carries the fungus and may infect other lilies in other ponds. The disease shows in the second or third year after the infection has taken place. There is only one protection: buy waterlilies from sources that are free of crown rot. Waterlily nurseries in Europe usualy take great care to keep their stock plants free from crown rot. New purchased waterlilies are kept under quarantaine and are planted into the propagation ponds after a long time of observation. Since tradespeople have to sell their purchased waterlilies after just a few weeks they do not have the oppurtunity to observe the plants long enough in quarantaine. Purchasing waterlilies from private vendors in the internet bears also the risk to introduce the disease unintenionally. Since it takes up to three years before the disease becomes obvious the vendor may believe to offer healthy plants although they already carry the infection. Unfortunatelly it is a waterborne disease and can travel to your pond with any kind of plant from an infected pond.