Once established, water plants usually grow very well, blooming and increasing in size with little need for much in the way of encouragement or assistance – which can make a pleasant change from the more demanding varieties in the rest of the garden. However, this vigour can prove a bit of a problem if aquatic plants are left entirely to their own devices, since they may well eventually prove a bit too successful and end up choking the pond. Getting the right balance between a good show of vegetation and the right amount of open water calls for a little management and keeping plant growth – and overgrowth – under control.
Thinning Out Your Pond
Once the water has been warmed up by the spring sun and the plants have been actively growing for a while, it is a good idea to thin out those which have started to get too big or are beginning to crowd out other plants in the pond. This is usually a good job for the early summer, before things get too out of hand and while there will still be enough time for the plants to recover and put on another burst of growth. It is also a good opportunity to divide plants either to increase their numbers in your own pond or alternatively exchange with fellow water gardeners for other plants that you want to grow. Any container grown water plants which have become root-bound should be divided – prising them apart by hand or between two garden forks held back-to-back, or cut with a knife if the root mass is too resistant to being separated in this way. The resulting clumps can then be re-potted individually.
Some forms of water weed – notably Canadian Pondweed (Elodea canadensis) – can be very vigorous indeed and their fast growing underwater fronds can quickly overgrow and entangle other submerged plants. It is often worth checking to see how much weed growth there has been at the same time as lifting your containers for division. Thinning out water weed is a relatively simple job and can be done by hand in small pools, and using a garden rake if the pond is bigger and the water deeper. If you intend discarding or composting it, leaving it beside the pond for a few hours first gives any small creatures that may be hiding amongst the leaves the chance to make their way back to the water.
Although thinning out is an important part of routine pond maintenance, it shouldn’t be done too drastically; if you thin out all the plants in one go, changing the conditions so suddenly may not suit the pond-life – and the additional light filtering through may encourage algae. It is a job best spread over two or three sessions, to avoid making the changes too extreme.
Trimming and Cutting Back
Keeping plants trimmed as they need it is one of the best ways to keep on top things, but it is not simply about keeping them looking at their best. Excess vegetable matter is one of the major contributors to silt in ponds – and this is a particular problem towards the autumn as the plants begin to die back for winter. Removing dead or damaged foliage on a regular basis, helps reduce the formation of sludge on the bottom and makes the need to clean the pond much less frequent. For the same reason, once the growing season has pretty much come to a halt, prune the plants around the pond as well as the ones in it; cutting back any overhanging vegetation which may otherwise fall into the pond during the winter can make a big difference.
So much of keeping a healthy water garden comes down to maintenance in one form or another – and managing the vegetation is no exception. Keeping the plants under control is not particularly difficult and brings a number of benefits. Even in these days of the near-universal use of UV clarifiers and bio-filters, for example, which have effectively done away with the traditional twin algal scourges of green water and blanket weed, plant management can still play its part. For all of these advances in technology, clearing out decaying plant matter and keeping your pond’s surface half or two-thirds covered with vegetation both remain sound tips for keeping down algae.
From a practical standpoint, routine thinning out, trimming and cutting back ensures that the pond stays at its best and provides the right conditions for fish, pond-life and the plants themselves. A well-managed pond is clearly a much healthier place than one choked by rampant weed-growth – and it looks a whole lot better too!