If you have always purchased your pond plants ready-potted from a garden centre, you may feel uncertain what to do when your bare-root pond plant arrives, but it’s really not difficult. If you are planting a bog garden, or if you are lucky enough to have a natural pond, you can just dig a hole and plant your plant straight into the ground as you would any garden plant. Most pond plants appreciate plenty of room for their roots, and will perform very well when planted out like this. If you are planting deep-water plants such as waterlilies and you have an exceptionally large natural pond – too large and deep for you to reach the centre to dig a hole – you can wrap the roots of the plants, together with some soil and a medium-sized stone for weight, in a square of hessian. Pull this up around the roots and soil to make a ‘bag’ and tie some string loosely around the top of the bag to hold the hessian in place. You can then gently throw the plants out to where you want them to be and they will sink on to the pond bottom.
Otherwise you should pot your plant, and simply place the pot in the pond. You can use normal plastic garden pots (those with solid sides and just 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. If you use open-mesh baskets, note that you may need a hessian basket liner to hold the soil in, depending on how large the basket mesh is and how fine the soil is that you are using. 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 and miniature waterlilies can be started in pots of around 1 litre capacity, but most pond plants are best started in pots of 2 to 5 litre capacity. We would generally recommend that each variety of plant is potted individually, so that they are not competing for space in one pot.
Pot the plant in a heavy, loam-based soil. Special aquatic soil is available in most garden centres, or 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.
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 by pushing either something like a Pond Spike into the pot, or (if the soil is soft and you don’t mind getting dirty hands) by pushing something like a Fertiliser Ball down into the soil until it is around the plant’s roots. Other pond plants will also benefit from being re-potted or divided regularly, but it is less important in these cases, and they do not generally require any added fertiliser in spring.