How to Maintain a Garden Pond in Winter
Preparing for the winter
It is surprising how many gardeners neglect their pools once the last waterlily blossom has faded. The dull wet days of autumn descend and they take to their firesides thinking, that like on the vegetable patch, nothing is happening in the pool. This is regrettable, for more trouble can ensue from neglecting a pool in the autumn than at any other time of the year.
The first problem to be tackled is that of falling leaves from surrounding trees. Even a small accumulation in the bottom of the pool can be dangerous, particularly if like horse-chestnut, they are toxic as well. A fine mesh net placed across the pool is absolutely essential until the trees are bare.
Marginal plants must be cleaned up once the frost has turned the foliage brown. Reduce them by about two-thirds of their height. Never cut them below water level, for some aquatics have hollow stems and will actually die from drowning. However, it is important that they are all tidied up so that they do not become a winter refuge for insect pests.
Waterlilies need no winter preparation as they are perfectly hardy and die down naturally without fuss. We only need feel concern for pygmy varieties in a rock pool or sink, as these can be damaged by severe weather. The best method of protection is to drain the water off and then give the waterlilies a liberal covering of straw. They survive well like this and can easily be started into growth again in the spring by the addition of water.
Floating plants disappear one by one as the days shorten, retreating into winter buds or turions which fall to the pool floor where they remain until the spring sunshine warms the water again. As I mentioned when describing various floating plants, it is useful to collect some of the over-wintering buds and keep them in jars of water with a little in the bottom. If stood in a light frost-free place they start into growth much sooner and are an invaluable aid in the battle against algae. By being well advanced they provide surface shade during early spring, a good few weeks before those that are resting naturally on the pool floor appear.
Fish should be prepared for the winter by judicious feeding with daphnia, ant eggs and other delicacies on days when the weather is warm and bright and they are seen to be active. Precautions for their winter welfare should be taken at this time with the introduction of a pool heater.
The garden pool in winter
The pool in winter is an inhospitable place and often causes concern to the newcomer to. Worries about the safety of the are quite natural, but providing sensible precautions are taken the majority will come to no harm.
Most decorative coldwater fish are extremely hardy. During the winter their metabolism slows down much in the same way as a tree becomes dormant. Therefore, being inactive they feed less. So please refrain from feeding them at all during the winter. Uneaten fish food will just fall to the floor of the pool and decompose. This semi-dormant state is particularly valuable to fish, enabling them to be frozen more or less solid in ice for a few days without apparently coming to any harm. In fact, a prolonged period with a layer of ice over the surface of the pool is likely to cause more casualties owing to the build-up of noxious gases beneath.
In a well-maintained pool the problem of gases is not so acute as there is much less organic debris to decay. But once a layer of ice has formed there is no way of knowing exactly what is going on beneath and it is a wise precaution to keep at least a small area free from ice.
The simplest method of doing this is by installing a pool heater. This consists of a heated brass rod with a polystyrene float which can be connected to the electrical supply which operates the pump. Even in severe frosts this will create a small ice-free area. If electricity is not close at hand, the safest way of obtaining a similar effect is by standing a pan of boiling water on the ice and allowing it to melt through. Never strike the ice with a heavy instrument as this will concuss and often kill the fish.