How to Manage a Wildlife Pond Through the Summer Months

The pond surface tells you a great deal about how summer is going. Right now, in early July, mine has developed that slightly glazed look that comes from a combination of warm water, full sun, and the quiet, relentless ambition of blanket weed. The irises have finished flowering and their foliage is starting to flop. A family of blackbirds has apparently decided that the shallow end is their personal bathing facility. And somewhere beneath the surface, the water is doing all the complex, invisible work that makes a wildlife pond worth having.

Managing a garden pond through summer is not dramatic. It does not require specialist equipment or a weekend of major intervention. But it does require attention, and a willingness to keep returning to it through the warmest months rather than assuming that because the pond was in good shape in May, it will look after itself until September. It will not.

Blanket Weed: Remove It Regularly, Not Occasionally

The single most pressing job through June, July, and August is managing blanket weed, the common name for the filamentous green algae that forms long, silky strands and can cover a small pond surface with startling speed in warm, sunny weather. It thrives in exactly the conditions a summer garden provides: warmth, light, and water that is often slightly nutrient-rich from decaying plant matter or, if you have topped up from the tap, a trace of minerals.

The most effective method is also the simplest. Twist a long stick or cane into the blanket weed as if you were winding spaghetti onto a fork, and lift it clear of the water in great sodden ropes. Do this little and often rather than waiting until it has established a serious hold. Once or twice a week through the height of summer is not excessive for a pond in a sunny position.

There is one important step that many people skip: leave the removed weed at the pond's edge for twenty-four hours before moving it to the compost heap. This allows any invertebrates, water snails, or small creatures tangled in it to find their way back to the water. It feels like a minor courtesy, but a productive pond is full of life you cannot easily see, and that life is worth keeping.

Barley straw can help suppress blanket weed growth over time. A small barley straw pad, the kind sold specifically for ponds, placed in the water as the season warms up, releases compounds that inhibit algal growth without harming the wider pond life. It works slowly and preventatively, not as an emergency cure, so it is better introduced in spring than as a panicked response to a July bloom.

Water Levels in Warm Weather

A hot, dry July can drop the water level in a small garden pond by several centimetres a week through evaporation alone. This matters more than it might appear. Shallower water warms more quickly, which stresses aquatic life and accelerates algal growth. Plants rooted in the marginal shelves may find themselves in water that is too shallow to support them properly. And a pond that drops significantly exposes liner edges or coping stones that can crack in sustained heat.

The instinct to grab a hosepipe and bring it back up quickly is understandable, but worth moderating. Topping up little and often is much less disruptive to pond life than a large, sudden volume of cold tap water introduced all at once. Tap water is also typically harder and slightly more alkaline than rainwater, and contains chlorine, all of which are tolerated in small amounts but accumulate if the pond is regularly topped up this way through a dry season.

If you have a water butt, use it. Rainwater is always preferable, and if supplies allow, a slow, gentle addition every few days is far kinder than an intermittent drench. If tap water is all you have, fill a watering can and leave it to stand for a few hours before adding it, which allows some of the chlorine to dissipate. Top up in the morning or evening rather than the hottest part of the day.

Marginal Plants: Which Are Earning Their Keep

Summer is the season when you can properly assess which marginal plants are doing useful work and which are simply taking over. The distinction matters, because an overgrown marginal shelf covered entirely in foliage is doing rather less for wildlife than a mix of planted edges and genuine open water.

Yellow flag iris (Iris pseudacorus) is one of the most commonly planted marginals in British gardens and, left unchecked, one of the most aggressive. By July it will be producing substantial new growth from its rhizomes. If yours is encroaching noticeably on open water, now is a reasonable time to lift a portion of the root mass and remove what you do not need. It divides easily and can go on a compost heap or be offered to a neighbour with a new pond. Keep some, certainly, the upright foliage provides structure and the spent flower stems are useful for emerging invertebrates, but not so much that it dominates the pond edge.

Brooklime (Veronica beccabunga), marsh marigold (Caltha palustris), and water mint (Mentha aquatica) are all excellent choices for British wildlife ponds and generally better behaved. Water mint in particular provides good late-season forage for bees and is tolerant of fluctuating water levels, which makes it a practical choice for ponds that experience the summer drops described above.

What you are aiming for, regardless of which species you grow, is a pond where roughly half the water surface remains open and accessible. Open water allows light to penetrate, supports submerged oxygenating plants, and gives amphibians, birds, and insects the access they need. A pond that is covered entirely in lily pads or choked with marginals may look lush, but it is functioning below its potential.

Submerged Plants and Oxygenation

Oxygenating plants do much of the real work in a healthy pond, and they are easy to overlook because you cannot see them doing it. Through summer, submerged plants like hornwort (Ceratophyllum demersum) and water starwort (Callitriche stagnalis) photosynthesise actively in warm water, releasing oxygen and competing with algae for the nutrients that drive algal blooms. They also provide shelter and spawning habitat for aquatic invertebrates.

If your oxygenators have become very dense, they can be thinned carefully by hand, removing roughly a third of the mass and composting it. If they are sparse or absent, summer is not the ideal time to introduce new plants since the water is warm and the competition from algae is strong, but a small addition of hornwort, weighted with a pebble and dropped into the deeper section of the pond, will generally establish itself well enough.

The balance to aim for is enough submerged plant matter to keep the water clear and oxygenated, without so much that it fills the mid-water column and prevents movement or light penetration. A reasonably clear pond in July, one where you can see the bottom in the shallower areas, is generally a pond in decent health.

Managing the Pond Margins on Land

The area immediately surrounding a wildlife pond is often given less thought than the water itself, which is a missed opportunity. A well-managed pond edge does a great deal to support the creatures that depend on the water.

Long grass left uncut within a metre or two of the pond provides shelter for frogs, newts, and toads moving between the water and the wider garden. Amphibians are far more vulnerable on land than most gardeners appreciate, and a strip of rough vegetation at the water's edge is not untidiness, it is habitat. If the thought of long grass conflicts with the general garden aesthetic, a narrow mown path between the pond and the rest of the garden satisfies both.

Avoid using any pesticides, slug pellets, or chemical treatments within several metres of the water. This applies to the surrounding beds and lawn as well as the pond edge itself. Frogs and toads, dear reader, are doing considerable work on your behalf with the slug population, and they move freely between the pond and the rest of the garden. Keeping that corridor clean matters.

A flat stone or two at the water's edge, partially in the water, partially out, gives birds and hedgehogs a place to drink safely. A pile of logs or stones near the margin provides overwintering and shelter habitat that will pay dividends from late summer onwards as amphibians begin looking for places to settle for the colder months.

In my own garden, the pond margins are where I have found the most wildlife by simply being still for a few minutes: common blue damselflies resting on the iris leaves, a slow worm making its way through the grass, a great tit taking an exploratory bath in the shallow end. None of it requires management so much as restraint: the willingness not to tidy everything, not to intervene at every opportunity, not to mistake productive wildness for neglect.

Return to the pond every week through July and August, remove the blanket weed before it establishes itself, check the water level, and keep the margins slightly rough. That is the sum of it, and it is more than enough.