Pond plants are the engine room of a healthy wildlife pond. They oxygenate the water, shelter tadpoles and newts, and give dragonflies somewhere to climb out and dry their wings. A little seasonal care keeps them vigorous, stops the thugs taking over, and leaves room for frogs, insects and brookside creatures.

Spring: Waking the Pond Gently

As light levels rise and the water warms, pond plants start into growth. Look, but do not launch a major clear-out. Frogs, toads and newts may still be spawning, and tadpoles graze on algae and soft plant tissue. Wait until late spring, once tadpoles have legs, before pulling out great handfuls of weed.

Do tidy obvious debris, but check it first. Newt eggs are often wrapped in folded leaves, and frogs shelter in damp margin debris. If you have baskets of marginals, lift them carefully and check roots are not escaping. Begin a gentle spring feed with specialist aquatic fertiliser tablets once you see fresh green growth. Hold off if the water is below about 10°C, as plants will not take up nutrients well.

Dividing and Replanting Overgrown Clumps

By late spring or early summer, many pond plants become congested. The signs are clear: smaller leaves, fewer flowers, roots matted around the basket, water pushing over the rim. Dividing rejuvenates the plant, keeps it in bounds, and gives you free plants to spread along a brookside.

• Marginals such as flag iris, water mint and flowering rush: lift the basket, split the rootball with a sharp knife or two forks, discard the tired centre. Replant a healthy outer piece in aquatic compost, top with grit, and water well.
• Water lilies: divide rhizomes in late spring, keeping one growing point and a good set of roots per piece. Plant horizontally in a large basket, growing tip just above the compost.
• Oxygenators such as hornwort and water starwort: trim long stems and replant cuttings in small bunches weighted with a stone. Never release non-native oxygenators into a brook or wild pond.

Work in sections rather than clearing the whole pond. Leaving half the plants undisturbed protects the tiny invertebrates that fish, newts and birds rely on.

Feeding Pond Plants Without Feeding Algae

Aquatic plants in baskets have a limited larder. Over a season they can exhaust the compost, especially if flowering freely. Use a slow-release aquatic fertiliser tablet pushed into the compost at the base of the plant, not scattered into the water. Follow the packet rate, and use less rather than more.

General garden fertiliser is a false friend. It dissolves into the water and feeds blanketweed and green water instead of your lilies. If you garden on a brookside, keep fertiliser well away from the bank; runoff travels further than you think. Feed only during active growth, from mid-spring to late summer. After August, stop. Marginals in open soil at the pond edge usually need no extra feeding.

Controlling Strong Growers and Blanketweed

Some pond plants are beautiful but boisterous. Reedmace, greater pond sedge and water mint can double their patch in a season. Control them by hand, pulling or cutting before they set seed, and dividing regularly. Duckweed is best netted out little and often; a small amount is useful, but a complete carpet blocks light and starves oxygenators.

Blanketweed thrives on sunlight and excess nutrients. Twirl it out with a rough stick, then leave the bundle on the pond edge for a day so water fleas, snails and newt larvae can crawl back in. Long-term, aim for shade: water lilies or floating heart covering a third to a half of the surface will cool the water and slow algal growth. Never use algicides, as they harm the whole food web.

Along a brookside, plant banks with moisture-loving natives such as meadowsweet, purple loosestrife and sedges. Their roots bind soil and filter runoff, while flowers feed bees and hoverflies.

Summer Care and Wildlife Watch

Through summer, keep the water level steady with rainwater from a butt. Tap water contains nutrients that encourage algae, so use it only as a last resort. Top up little and often. Check oxygenators after heavy rain; they can be pushed to the surface or buried under silt. Thin them if they cover more than about half the water, as fish and amphibians need open water to surface.

Deadhead faded lilies and marginals, but leave some seedheads for goldfinches and insects. If aphids cluster on lily leaves, spray them with a jet of water rather than insecticide. Watch for frogs sitting on leaves and dragonflies emerging from stems. Their presence is the best sign your planting is working. A gentle trim now prevents a bigger job in autumn.

Autumn and Winter: Leaving Structure for Wildlife

As growth slows, resist the urge to cut everything down. Hollow stems of reed and iris make winter homes for insects, and seedheads feed birds. Remove only collapsing or slimy foliage, and net out excess fallen leaves before they sink and deoxygenate the water. Leave a few leaves at the margin as cover for frogs and newts.

Stop feeding aquatic plants by early autumn. If you need to divide or replant, wait until spring. In cold spells, do not smash ice; the shock can harm fish and amphibians. Instead, melt a hole by resting a pan of hot water on the surface. Through winter the pond may look quiet, but beneath the surface roots, buds and hidden creatures are waiting. Your seasonal care will bring them back stronger, and your brookside landscape richer.