Choosing Pots, Soil and Fertilisers for Pond Plants
When potting a pond plant, you can use normal plastic garden pots (those with solid sides and the holes in the bottom) like any other potted plant if you wish. However, if possible, opt for open-mesh aquatic baskets; these allow greater contact between the plant’s roots and the pond water, and plants generally grow better in them. Most modern open-mesh baskets have quite fine mesh and do not usually require a hessian liner to hold the soil in, but if you are using very fine powdery soil or a basket with a very open mesh, you may still need a liner. Newspaper will do as a liner if you have nothing else, but bear in mind that it is not long-lasting in the way that hessian liners are and may disintegrate if the pot is disturbed later. An alternative to pots is to use aquatic planting bags – these are flexible, permeable, mesh bags which will not leach soil out and which can be fitted into awkward places.
Do ensure that whatever pot you choose gives your plants enough room. Many aquatic plants, and waterlilies in particular, need the space for a large root area. Do not place these in small or cramped pots if you want them to perform and flower well. Small marginal plants, oxygenators, and miniature waterlilies can be started in pots of around 1 litre capacity, while larger marginal plants and other waterlilies are best started in pots of 2 to 5 litre capacity. We generally recommend that each variety of plant is potted individually, so that they are not competing for space in one pot. You can find more specific information on each plant's page on our website.
Pot the plant in a heavy, loamy soil. This is a soil which is composed of sand, silt and clay, rather than being a peat-based soil (which will tend to float). If you are potting waterlilies or deep-water plants such as Orontiums you can even use a heavy clay soil. Special aquatic soil is available in most garden centres and this works well. Alternatively, normal garden soil from somewhere like a flowerbed, that has been raked or sieved to make it workable, can be used. Do not use standard potting compost or any garden soil that has recently been fertilised, as this can cause excessive algae and/or green water in the pond.
When growing pond plants in pots, we would advise that waterlilies and water irises are re-potted or divided every two to three years, for best results. We would also advise that waterlilies are fertilised once a year, ideally in spring, if you are not re-potting them that year. It is best to use special aquatic plant fertiliser, as standard plant fertilisers can dissolve and leach out into pond water. You can fertilise a plant without re-potting it, if you don't mind getting dirty hands, by pushing a slow-release fertiliser tablet down into the soil until it is around the plant's roots. All other pond plants will also benefit from being re-potted or divided every two to three years, but it is less important in these cases, and they do not generally require any added fertiliser in spring.