Spring Tasks for a Healthy Wildlife Pond

Wake-Up Call: Reading the Signs in Early Spring

By mid-March, most British ponds are stirring back to life. Water temperatures creep past 8°C in the shallows, frogs and toads begin their migration back to breeding water, and the first midge and damselfly larvae start moving about in the silt. If you have kept an eye on your pond through the winter, you will already have noticed the water clearing as algae die back and submerged plants tick over slowly in the cold.

Early spring is arguably the most important few weeks of the pond-keeping year. Get a few jobs done now, while plants are still dormant and creatures are fewer and slower, and you will spend the rest of the season enjoying a balanced, healthy pond rather than fighting it. Late March to mid-April is the sweet spot for most of the UK, though in northern Scotland and upland areas you may be a fortnight or more behind.

Clearing Blanket Weed Without Harming Wildlife

Filamentous algae, usually lumped together as blanket weed, begins to lengthen as light levels rise and nutrients become available. A little is completely natural and provides cover for tadpoles and small invertebrates. The trouble starts when it forms long, smothering mats across the surface.

Twist it out rather than trying to net everything at once. A rough stick or a dedicated rake works well: catch a strand and twirl it gently, and the weed lifts away in satisfying ropes. Whatever you remove, leave it on the pond edge for a day so that any trapped insects, newts or tadpoles can crawl back into the water.

• Never strip it all. Clear no more than about half of what is there at any one time.
• Tackle the cause. Algae thrive on nutrients, so reduce run-off from fertilised borders, leaf litter and overfeeding.
• Add competition. Oxygenators such as hornwort and water starwort take up nutrients and shade the water, making blanket weed far less vigorous.
• Consider barley straw in a mesh bag, weighed down near the surface, as a slow-acting suppressant rather than a quick fix.

Dividing and Reinvigorating Overcrowded Plants

After three or four years, most marginal plants have filled their baskets and started to push out of them. Crowded roots reduce flowering, leave less open water, and make it harder for amphibians to move around. Early spring is the ideal moment to divide them, before fresh growth makes the job messy.

Lift the basket, lay it on a tarpaulin and use a hand fork or an old bread knife to split the clump. Keep the firm, healthy outer pieces and throw the tired, woody centre onto the compost heap. Replant in aquatic baskets using a heavy loam-based compost rather than multipurpose potting compost, which is too light and far too rich. Top the surface with a layer of pea gravel to stop the compost floating away and to deter birds from scattering it.

As a rough guide, aim for about a third to a half of the surface to be covered by floating-leaved plants, with open water left clear for birds to bathe and amphibians to swim. If the pond has filled with duckweed or floating pennywort, remove what you can by hand, though be aware that pennywort is an invasive non-native species and any fragments must be bagged and binned, never returned to a waterway.

Frogspawn, Newts and Other Arrivals

Frogspawn usually appears first, in clumps of jelly with black embryos at the centre, often in the shallowest, sunniest corner. Toadspawn follows as strings wound around plant stems, and smooth newts lay eggs singly, wrapping each one in a folded leaf. Each is a good sign that your pond is functioning as a habitat rather than simply as a water feature.

Resist the urge to move spawn between ponds. Disease, including ranavirus and chytrid fungus, spreads easily on wet hands and equipment. If your pond dries out or the weather turns hard, do not panic. Frogs can cope with a cold snap, and the jelly insulates the eggs surprisingly well. Do check, though, that pond levels are topped up.

• Leave the edges messy. Long grass, log piles and stone crevices give amphibians somewhere cool and damp to retreat to.
• Build a shallow beach. A gently sloping, pebble edge lets hedgehogs and birds drink and climb out safely.
• Watch for cats and herons. Dense planting at the margins is the simplest, most effective deterrent.

Water Levels, Rainwater and the Spring Clean-Up

Winter rain often leaves ponds full, but a dry, breezy March can drop levels quickly. Top up with rainwater from a butt wherever possible. Tap water contains chlorine, phosphates and nitrate, all of which feed algae and can upset the delicate balance of a wildlife pond. If you must use tap water, let it stand for a day or two first and add it in small quantities.

Remove fallen leaves and debris from the bottom with a net, working from the shallow end and checking the contents carefully before emptying. Do not be tempted to empty and scrub the pond. That layer of silt and algae is the engine room of the whole ecosystem, home to dragonfly nymphs, water boatmen and countless microscopic creatures. A gentle tidy is all that is needed.

Finally, check any pump or filter, remove the protective netting you may have put over the pond in autumn, and give yourself a moment to simply sit and watch. The best ponds are the ones left largely to their own devices, nudged along gently each spring rather than managed to within an inch of their life. Do the groundwork now, and by June you will have a pond humming with life with barely any effort at all.