A spring pond clean

Spring is when a pond looks its worst. The winter has left dead leaves on the bottom, collapsed stems at the edge and a film of debris on the surface. It is tempting to drain the whole thing and start again. For most garden ponds, and almost every wildlife pond, that is the wrong job at the wrong time of year.

A spring clean is a light tidy. The deep clean, if the pond ever needs one, is an autumn job.

Why spring is the wrong time for a big clear-out

By early spring, frogs, toads and newts are returning to ponds to breed. Spawn, then tadpoles and newt larvae, live in the water and among the plants for months. Emptying or heavily dredging the pond in that season removes the animals the pond exists for.

The RHS care advice says ponds rarely need a complete clear-out unless they have become extremely overgrown or silted up, and that when one is needed, the best time is early autumn, when many creatures are less active. The RHS wildlife pond guide says it is generally best to disturb a wildlife pond as little as possible. So the default in spring is: do not empty the pond. If you can avoid it, do not drain it at all during the amphibian breeding season.

If something forces your hand, such as a split liner, a pump failure that threatens fish, or a safety change, see the "If you really must drain it" section below and get the order right.

What a spring clean does include

Leaves on the surface and in the shallows.

Lift floating leaves with a net. Rake out what you can reach easily in the shallows, where it is clearly dead material. Go gently. Spawn and young animals sit in the same places. A few leaves left on the bottom are not a problem. The RHS wildlife guide says there is little evidence that a light fall of leaves harms pond life.

If a leaf net went on in the autumn, take it off now if it is still there. Pond winter care explains why the net is an autumn tool.

Dead and tatty growth.

The RHS care page says to remove dead, tatty or fading leaves so they do not decompose in the water. In spring that means last year's collapsed marginal stems and the brown leaves of waterlilies, cut or pulled where they meet the water.

Pumps and filters.

If you took a pump out for the winter, check it over and clean the strainer before it goes back. Rinse filter foams in pond water rather than under the tap, so you do not knock back the useful bacteria. Unplug or isolate anything electrical before you handle it, as the electrics page says.

Blanketweed.

Blanketweed often appears as the water warms. Twirl it out on a stick and leave it on the bank so animals can crawl back. Blanketweed has the full method.

When to leave plants alone

Many marginal plants look dead in early spring and are about to send up new shoots. Cut away clearly dead stems at the base, but do not pull up whole plants that are simply slow to start.

The RHS suggests leaving faded marginals until late winter, because they give invertebrates cover. By spring that cover has done its job, and tidying is reasonable. Leave some stems standing near the water for dragonfly and damselfly larvae to climb later in the season. The plants guide lists the jobs each plant group does.

If a plant has outgrown its basket, dividing it is usually better done once it is in active growth. Lift it gently, check it for spawn and larvae, and put back any animals you find.

Sludge can usually wait

Sludge, or silt, is the soft layer of rotted leaves and soil on the bottom. A thin layer is normal and is part of the habitat. The RHS wildlife guide says to avoid removing accumulated sediment if possible. If removal is essential, it says to tackle it in early autumn and to remove only half the excess sediment at a time.

So in spring, leave the sludge where it is. If the pond is shallowing up badly, note it and plan a partial clear-out for early autumn.

If you really must drain it

Sometimes there is no choice. The Freshwater Habitats Trust FAQ gives a sensible order:

• If you can avoid emptying the pond fully, they suggest leaving about an inch of water in the bottom.
• If you must drain it completely, do it slowly, so creatures that can fly away have time to do so.
• Small animals and plants can go into a temporary container. Adult amphibians can go to a damp, shaded spot.

Keep the removed water and the animals together, refill with rainwater where possible, and put the animals back as soon as the work is done. If there are fish, ask an aquatic specialist how to hold them safely.

A new pond in its first spring

A pond dug over the winter may be getting its first plants and visitors in spring. Starting a new pond covers that first season. Most of a spring clean does not apply yet. The job is to wait and plant.

The wildlife pond rule of thumb

For a pond built as described in how to build a wildlife pond, a spring clean is mostly a short walk round with a net and a pair of secateurs. Anything bigger can wait until autumn.

Can I clean my pond in March or April?

A light tidy, yes: floating leaves, dead stems and blanketweed. A full clear-out, no, if you can avoid it. That is breeding season for amphibians. The RHS points to early autumn for bigger jobs.

Should I remove the sludge every spring?

No. A thin layer of silt is normal. The RHS wildlife guide says to avoid removing sediment if possible, and if it must go, to do it in early autumn and take only half at a time.

There is frogspawn in the pond and the water is green. What should I do?

Leave it. Green water in spring is common and usually eases as plants grow. Do not drain the pond or add chemicals with spawn in it.