Last updated Nov 2020
Updated from a series written by Alec and Val Scaresbrook for Koi, Ponds and Gardens magazine.
The imminent cold weather dictates the pond work for September as the shorter autumn nights begin to draw in.
Planting in September
Plant of the month: Japanese maple
Pond equipment: pumps and cold weather
Project: pond lighting
Fish: provision for cold snaps
Plant now
Many plants now begin to shut down for the winter, eventually shedding their leaves. But although they slow down, you need to plan now for maximum effect in spring. Plant early-flowering pondside plants now for them to establish well by next spring. (Try Thompson & Morgan ). Bog primulas (Primula spp) and marsh marigolds (Caltha palustris) both give a bold display.
Now is also a time to think about early-flowering bulbs. Whether for containers or to go in the ground, you need to plant them at this time of year because they need time to develop their roots before bursting into flower next year. If you’re not sure exactly where you want to plant them in the ground yet, or the ground isn’t ready, don’t be deterred. You can plant the bulbs in ordinary plant pots (preferably large ones) and plunge these into the ground. Next year you can lift out these pots and re-plunge them in a better position. You could even sink them into a much larger ornamental pot. After flowering has finished and the leaves have died down, you can plant them in their final position.
For ideas and further information, see our guide to bulbs.
Plant of the month: Japanese maple
Japanese maples (Acer palmatum; A. japonicum) are beautifully shaped shrubs that can grow into small trees. Their delicate leaves have five or seven lobes or thread-like divisions, with most having glorious autumnal colours, usually green, yellow or purple, before they drop. Now is the time to search out the plant and colour for you, so look at our detailed guide to choosing and growing these ornamental shrubs.
Whichever of these beautiful plants you choose, ensure you provide your maple with neutral soil or potting compost, site it carefully so it’s sheltered from strong winds and late frosts, and be aware that too much direct sunlight scorches its beautiful leaves and makes them look burnt.
Pump care – prepare for winter
Water feature pumps are vulnerable to frost damage so should be removed, drained, serviced and stored in a dry place until they are needed next year. The water feature itself should also be drained and stored indoors if it’s vulnerable to frost damage. Any other pumps that can be switched off for a short time without causing problems with your filters can be serviced now too. With most pumps all that’s required is for the pump housing, impeller and any pre-strainer to be cleaned. The wiring should also be checked over for any damage.
When refitting pumps, check all fittings and joints in the pipework and check the pipes for damage. Any damage or deterioration indicates that it’s time to renew them before disaster strikes. If you haven’t already got a spare pump in reserve and you keep Koi or other fish, you should act now and buy one as insurance. Then if your main pump fails, or has to be sent away to be repaired, you can keep your filters going and your fish in good health.
Water features, pumps and spares are available from Bradshaws Direct and Pondkeeper.
Project: install pond lighting
Even if you’re at home during daylight hours and don’t need outside lights for chores, you can still appreciate ornamental lights for their overall effect in the garden. Underwater lights, along with spotlights trained on favourite plants or ornaments, transform the night scene and enable you to enjoy your garden in the evening.
DIY kits for functional outdoor lights are readily available, some of which are solar-powered lighting so need no nearby electric socket or disguised cables. Similarly, it’s also easy to find low-voltage or solar-powered pond lights and garden spotlights. You may wonder if a solar-powered light will work during the winter, but ordinary daylight is enough to operate them. Some models also have battery back-ups. Take a look at the range from Bradshaws Direct and Pondkeeper.
Fit low voltage lights by connecting them to a transformer at or near your mains socket. Both the transformer and the socket must be housed somewhere that will be dry. Always remember to be safe; electricity and the outside elements do not make a good combination. Make sure you follow the installation instructions included with all of these lights.
Fish: provision for cold snaps
Feeding your Koi
Stock up with fresh supplies of high-carbohydrate winter feed (such as wheatgerm and other feed from Bradshaws Direct) ready to change with the weather. Switch to winter Koi food when the temperature drops below 12°C. As the demand for food falls, reduce the amount but continue to feed frequently.
Preventing ice
Some fish-keepers are content with keeping part of their pond ice free, but some Koi keepers heat the water to maintain year-round growth. Water is densest at 4°C, so in still ponds this water sinks to the bottom, which is therefore where fish and other creatures can survive the frost and snow in relative warmth. To prevent submersible pumps mixing the layers and disturbing the warmer water that’s collected at the bottom of the pond, raise them on a support of some sort.
Switch off all pumps to waterfalls and fountains because they will chill the water; if your filter outlet feeds a waterfall then avoid mixing the water by bypassing the waterfall with a temporary pipe.
To keep a small part of an unheated pond ice free, you can install a pond heating element, or if there’s no convenient electrical supply you can always float a polystyrene device on the surface. This will keep that area of the pond from freezing over. You can find various heaters and ice preventers for sale online, including from Bradshaws Direct and Pondkeeper.