Pond work for June

Last updated March 2018
From a series written by Alec and Val Scaresbrook for Koi, Ponds and Gardens magazine.

Is your garden ready for summer? Have you settled into a good routine? If not, now’s the time to start on our list of what pond work to do in June.

Plant of the month
Project: trellis

Marginal plants and bog gardens

Seeds germinate readily in the moist soil of bog gardens and pond margins, so it is a good idea to check your planted areas regularly for unwanted seedlings and pull them out as soon as you identify them. This prevents them developing a good root system that makes them difficult to extract later from the wet soil. You’ll probably be surprised at how many seedlings there are – this is because marginal and bog garden plants often produce copious amounts of seed, and wind-borne weed seeds grow successfully too. For access to a bog garden without damaging the plants or compacting the soil, stand on a board, as this will spread your weight.

Every few years, you should also split up and replant some bog garden plants, such as primulas, to maximise growth and flowering. To make it easier to untangle the roots, dig up the clump (carefully to avoid damage to the liner if it also lines the pond), and put the rootball in a bucket of water for a while. The soaked rootball is easier to work with, as you can wash off the soil more readily and ease the clump apart with the roots still intact before replanting where required.

Plant pests
Be on the look-out for pests and diseases affecting waterlilies. You may notice leaves covered in spots, beginning as a reddish sphere with concentric zones before spreading irregularly and becoming black. If you see this, remove and dispose of affected leaves. Beetles also feed on waterlily leaves, with the larval stages making holes and channels in the leaves so they eventually rot and fall apart. To avoid using insecticides, use a blast from a hosepipe to dislodge the adults and larvae into the water, where Koi will eat them.

Aphids are another pest for buds and leaves of aquatic plants. Brown or dark green, these insects feed on sap in summer, distorting plant growth. If you can reach, squash the aphids with your finger and thumb, or knock them off with a jet of water.

Duckweed control
You need to keep on with controlling duckweed – see pond work for May for more information.

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Some irises are moisture-loving and commonly referred to as water irises (from Thompson & Morgan ), although this covers various species, including Iris ensata, I. laevigata and I. setosa, often referred to as Japanese iris. They are ideal for shallow planting in ponds or in the wet soil of a bog garden or pond margins, thriving in sun or partial shade. Iris was the name of the Greek’s goddess of the rainbow, and is a highly appropriate name for this summer-flowering plant because you’ll find a wide range of colours and shades available. The blue, blue-purple, or white Iris laevigata looks good in and around water, growing 60-90cm (2-3ft) tall, with 2-4 flowers per stem from May to July. Others include Iris sibirica and the slightly earlier flowering Iris setosa. You’ll also see Iris pseudocorus, our native yellow flag, along canals and other wet places but it seeds and spreads too readily for most gardens, so avoid this one. There are garden versions, but they are also good at spreading, so are only for larger ponds and plots.

Even if you don’t have bog garden, damp pond margins, or a suitable pond shelf, you can still enjoy irises by planting them in your garden alongside your pool. Just buy those that prefer normal soil.

To have irises to enjoy immediately, buy plants sold in pots (see the range at Thompson & Morgan). For a display next year, plan ahead and order the rhizomes now for delivery in autumn. Check the soil requirements as often when irises are described as suitable for the side of a pond, this does not mean for damp soil but for normal garden border conditions. Our ‘how-to’ bulbs article gives some general advice for success.

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Project: erect trellis for modern ornamental screening

It’s never been easier to screen off parts of your garden, including the more unsightly paraphernalia of Koi keeping, or perhaps the shed. There are trellis panels available in all shapes and sizes, and lots of outdoor paint colours to customise your construction. Ornamental in its own right, trellis is also ideal for supporting climbing plants. You can attach trellis to the front of existing fencing to disguise it, or to the top of a fence for extra height without claustrophobia. Trellis can be used to infill between pergola posts, makes good windbreaks and shading for your Koi, and freestanding panels are useful for partitioning. As trellis isn’t prone to wind damage, it doesn’t need the heavy posts that are used for panel fencing. Instead, 60mm x 60mm (2in x 2in) are adequate and available from local timberyards although if you use one of the big suppliers, you might have to choose their smallest which is usually 75mm x 75mm. Dig post holes and set the timber in concrete (bags of ready-mix are available) or use shorter posts inserted into metal sockets. These are available as bolt-down versions for existing hard surfaces, or as spikes for driving into the ground. Just be sure you select the correct ones since they’re made for a range of post sizes.

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Mind that pond

There’s a lot for fish keepers to do during the summer months: checking leaks, water quality, filters, the health of the fish and cleaning the pond equipment. So it’s easy to forget that some routine gardening jobs could affect water quality and fish health.

Using a lawnmower without a grassbox usually leaves clumps of clippings on the lawn that can blow into your pond. Similarly, using a nylon-line trimmer spreads grass trimmings far and wide. A few pieces of grass in your pond won’t cause a problem, but large amounts add unwanted nutrients that encourage algal growth. The decomposition of grass in the pond also uses up oxygen and produces noxious gases, to the detriment of the health of your fish, especially Koi.

In addition to grass clippings, careless spreading of dry fertiliser or spraying of liquid feed will add nutrients to the pond and encourage algal growth. Pesticides can also cause problems, whether designed to kill weeds, slugs, insects, or fungi. When using them, temporarily cover the pond to prevent problems. If your pond is lower than the surrounding garden be careful that no chemicals are washed into the water by heavy rain.

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