Most books about water gardening include the bit about pond ‘weed’ in the section about pond plants, along with the rather more decorative flowering plants. In reality, however, there is only one real reason to have pondweeds, or oxygenating plants, in your pond, and that is to provide oxygen, which in turn helps to keep the water stable and in good condition. Of all the plants we can add to our ponds, these are perhaps the least interesting, yet they are almost certainly the most important. Let’s start with the basics.
If there are too many fish, or not enough plants (particularly the oxygenating type) in your pond, the water becomes short of dissolved oxygen. This manifests itself in fish either gasping for air at the surface, or lurking at the bottom, utterly disinterested in their food. If you add outside influences such as lack of water movement, and a spell of still, sultry weather that warms up the water so it can hold even less dissolved oxygen, you can very readily end up with some extremely sick fish.
Increasing the oxygen level in the water is not difficult. You can turn on the fountain or waterfall (if you have one), which will add and mix oxygen into the water as it tumbles and turns. However, if you have a still pond, the simplest thing to do is to make sure you have a plentiful and permanent supply of cheap and easy-to-grow oxygenating plants.
These are usually green, they rarely flower and seem to spend their lives suspended in the water, growing rapidly when your back is turned and never when you want them to. By day they convert dissolved carbon dioxide, given off by the fish, into oxygen. They also consume minerals and nutrients that otherwise would be used by opportunist and troublesome algae. A good selection of oxygenating plants will also provide effective cover for all manner of water creatures; fish will be afforded some protection against marauding herons, and spawning grounds will be provided for fish, amphibious and insectivorous wildlife.
Most garden centres will offer oxygenating plants from outside tanks and they are usually sold as small bunches of stems linked by a heavy metal weight. You just have to drop these bunches into the pond – you don’t need planting baskets or compost. The weights will take the bases of the bunches down, and they will find their own level, depending on the amount of leaves, and start to grow.
Most oxygenators will grow rapidly, especially during warm summers, and can cause the pond to become congested. You should, therefore, hook out a few bucketsful of excess weed, perhaps two or three times during the summer period. This will, curiously, make the weed grow faster, and in turn make it more efficient at filtering and conditioning the water. Carefully check through the foliage as you’re removing it, spread it out by the side of the pond and leave it for a day so that any creatures caught up in it, and which can crawl back into the water, are given the best chance.
Add the semi-dried weed to the compost heap. On no account be inclined to take it to your local pond or stream to keep it alive. Many misguided aquarists and pond owners have done this in the past, thus introducing plants that have quickly crowded out our native pond plant species and upsetting the whole ecology of our natural waterways.
It’s a good idea to select several species of oxygenator so that a variety of wildlife will be attracted. All wild pond-inhabiting creatures have their particular likes and dislikes, and a variety of foliage shapes and growth habits will offer the most habitats. Some of the best oxygenators include:
Autumn starwort (Callitrkhe hermaphroditica) A delicate plant, with vivid green foliage and fragile stems, that grows all year. It is prone to damage by heavy-finned fish.
Canadian pondweed [Elodea canadensis) Probably the most commonly seen oxygenator, it is hardy, vigorous and ideal for new ponds.
Curled pondweed [Potamogeton erispus) The long, crinkled leaves can be slow to establish, but are very sturdy, making the plant particularly good for ponds with waterfalls or fountains.
Hornwort [Ceratophyllum demersum) This free-floating plant has dark green, feathery foliage, and may need securing by tying to a stone or weight.
Water milfoil (Myriophyllum aquaticum) There are about 40 different water milfoils worldwide, all making superb perennial oxygenating plants with attractive blue-green or brown fern-like leaves in artistic whorls. But there are only a small handful that are regularly found in our domestic outdoor ponds.
Myriophyllum aquaticum is the most commonly seen, with very dense ferny foliage that emerges stiffly from the water. It is a tropical species and tends to die back in winter to dormant crowns that rest well beneath the surface of the water. These crowns then re-emerge in spring.
Herbs could be beneficial for you and you can also learn how to design a formal herb garden and also how to build a beach in your garden. Enjoy beaching within your house.