Now's the time for your pond's yearly service
There's a garden job I have not been looking forward to, so I've put it off year after year. But now it can wait no longer. The thing is, if we leave the little garden pond as it is for another season, it will cease to be a little pond and become a little bog. The modest clump of native yellow flag iris (Iris pseudacorus) planted 12 or 15 years ago has swelled to cover the pool bottom with a thick, tightly knit, fibrous mat of rhizomes and roots, while the oxygenating weed (some kind of Myriophyllum) has clogged up the small interludes of water between the iris stems. Our pond contains more nonwater than water, including the years of leaves and other debris that have fallen into it and that have been processed by unknown aquatic creatures into a fine, black mud (the best growth booster, incidentally, for putting at the roots of newly planted things in the garden).
Did I say I wasn't looking forward to clearing it out? I know it sounds like a messy, sloppy, wet operation - and it is. But, as I have just discovered after a sample half-hour of iris ripping and silt collecting, there is a primeval pleasure in playing in very soggy mud, as well as the squirmy thrill of encountering annoyed frogs in loathsome colours hiding under rocks on the edge (the adult frogs are wonderfully ugly).
It is mainly for the frogs' sake that we are restraining the pond from turning into a bog. Last spring the mating amphibians managed to find enough water to shoot their spawn into, but only just. And the tadpoles would probably have preferred a less congested ambit. If we clean it out now, in early autumn, there will still be time for the water to settle before cold weather, and the depths will offer their customary place for the frogs to hibernate over winter.
We don't have the pond solely as a habitat for frogs - although, of all the creatures that use it, they are the most interesting, what with the satisfyingly mucilaginous stages of their lifecycle. A body of water, especially one with a well-vegetated margin, is the best magnet for wildlife that a gardener can have.
Birds will come to bathe and drink, and bees and butterflies will arrive also. If you're somewhat rural, dragonflies and damselflies will come swooping in, to air dance and mate, and the eggs - laid in the water or on aquatic plants - will hatch into nymphs (the larval stage), which live underwater, breathing through gills. Hedgehogs and foxes will visit, too, if they're in the area, to quench their thirst.
The waters of the pond, of course, are home to a multitude of invertebrates: water beetles, water boatmen, pond skaters, pond snails, flat worms, water worms and a swarm of other minute blobby and bristly things. Dip a clean jar into a healthy pond and its contents will keep you occupied for hours. (When you're finished, don't forget to put the water, and everyone in it, back.)
If you have a pond already, now is the time to give it its yearly service. Rotting and dying vegetation should be removed, and oxygenating weeds that multiply quickly can be brutally reduced in volume. Other aquatic plants that have spread too much can be split and smaller sections of them returned to the water. Garden centres sell plastic baskets for pond plants, which allow air and water to pass through the roots. If there are large holes in the mesh, line with hessian or a similar material. Use poor garden soil in the containers, not potting compost, as this is too rich and can cause algae to thrive. Top the pots with gravel to prevent the soil floating off. If your pond has a muddy bottom you can plant right into it, anchoring the roots with a stone or brick - but be aware that plants on the loose like this multiply more quickly and may overwhelm less vigorous species.
Autumn leaves - how we resent them: proof that the summer-that-never-was will never be - disturb the balance when they fall into ponds and rot down. Fish them out as soon as possible or cover the pond with a net to keep them out.
If you are considering building a new pond, any time between now and early spring, when the ground is workable, is a good time to start. Consult a gardening book, or look at the websites listed below, before you get down to business. Choose your site carefully: away from trees (and their falling leaves) and in a sunny position. Bear in mind that water looks most natural in the lowest part of the garden, so don't be tempted to put your wildlife pond on an elevation. If you have toddlers, either forgo the pond until they are bigger or make sure that it is in a secure part of the garden.
Owners of new ponds are sometimes discouraged when their lovely clear water turns to pea soup overnight. This is a natural part of its development, as algae, fed by the nutrients in the water, multiply quickly. In a few months it will settle down of its own accord. Covering a third to two-thirds of the pond surface with plants will keep algae at bay. Some gardeners don't like duckweed, but it does compete with algae (and win). It earns a place in our pool, being the smallest flowering plant in the world and, as such, a tiny aquatic miracle.
• To find out more about setting up a pond see www.garden organic.org.uk/factsheets/gg29.php; for maintenance see www.gardenorganic.org.uk/factsheets/gg34.php; and for making a wildlife pond see www.ipcc.ie/watergarden.html
POND PLANTS
OXYGENATING PLANTShelp maintain pond balance. Try water milfoil (Myriophyllum spicatum and M. verticillatum), water crowfoot (Ranunculus aquatilis) or curled pondweed (Potamogeton crispus).
FLOATERSprovide surface cover and help prevent algae. Try frogbit (Hydrocharis morsus-ranae) or yellow floating heart (Nymphoides peltata).
DEEP-WATER PLANTSinclude water lilies, some of which require different depths of water. Check the label to make sure a plant is suitable for your pond's dimensions.
MARGINAL AND BOG PLANTSgrow in the shallows and moist ground at the edge of the pond, providing shelter for creatures and shade for the water. Natives are yellow flag iris (Iris pseudacorus), marsh marigold (Caltha palustris) and bulrush (Typha species). Non-natives include skunk cabbage (Lysichiton species), Iris laevigata and I. versicolor, monkey flower (Mimulus species), primulas, arrowhead (Sagittaria species), pickerel weed (Pontederia cordata) and arum lily (Zantedeschia aethiopica).
Never release aquatic plants into the wild, as they may choke water courses, damage the natural habitat and threaten biodiversity. The following are especially invasive: fairy fern (Azolla filiculoides), New Zealand pygmy weed (Crassula helmsii), floating pennywort (Hydrocotyle ranunculoides) and parrot's feather (Myriophyllum aquaticum).