Pond Plant Care

For a small to medium pond there is no need to add fertilizer to the planting compost as a matter of course. It may have a detrimental affect on the pond as it will dissolve quickly and cloud the water as it will feed the algae with mineral salts.
For large waterlilies in large areas of water nutrients can be added, but in small areas of water you should wait at least a year before using any. The best option then is to add a low release fertilizer in the form of a sachet that can be pushed into the container. Only use this type of sachet, recommended for waterlilies as unlike normal fertilizer it will not dissolve rapidly and lessens the risk of speeding the algae growth.

Aquatic plants can grow very quickly and can soon become overgrown, even if you have tried to restrict them by placing them in a small container. Therefore, pruning will soon become a necessity, particularly of the oxygenators. If it is not done regularly the soft, sappy growth will die down in the winter and pollute and deoxygenate the water. To prune them, simply nip the growth off at the base, leaving short stems. Young growth can be used as cuttings, if you want to increase your stock, but the stems will soon regrow. Mid to late summer is the best time to do this.

All plants can be affected by pests, parasites and disease at some time or another and your aquatic plants are no exception. However, most of them tend to cause problems to the appearance of the plant rather than causing you to lose the plant altogether.
There are obviously going to be restrictions on the way you use chemicals if there are fish in the pond as they will be seriously affected by these and fatalities will be high. Therefore, a biological approach is needed when treating any problems, and in some cases the fish can actualy help with this. Pests such as insects occur above the pond on the leaves of the plants but if you spray them with water they will fall into the pond where the fish will readily feast on them for you. If chemical treatment is needed it is best to remove the plant from situ, immerse it in a bucket of the diluted treatment for up to an hour, remove and rinse thoroughly, and then rinse some more, before returning to the pond.

There are only a few diseases that affect aquatic plants, the main one being fungal leaf spot. One attacks waterlilies and causes spots on the leaves that sometimes develop into dark patches and dry, brown edges. The affected leaves should be removed by hand as this is the only alternative to spraying with fungcides, which is not an option if there are fish in the pond.
Irises can also get leaf spot, it shows itself as random brown spots that sometimes elongate into brown streaks following the direction of the veins. Leaves can be removed as before, however, if they are far enough from the water to prevent any drift a wide-spectrum fungicide can be used if the disease is caught early enough. Follow manufacturers instructions and used on a very still day.