Oxygenating plants are vital for maintaining a healthy garden pond. They grow mainly underwater, producing oxygen and absorbing impurities, which help keep the pond clear and clean. They also limit the spread of unwanted algae by competing with them for nutrients.
Submerged plants produce oxygen during the day and provide cover for aquatic life, such as newts and frogs. Some oxygenators have dual functionality, being only partly submerged. This boosts oxygen levels in the water, while leaves and stems above the water level offer shade, protection and food for wildlife.
Choose native plants as they’ll withstand cold and ice through the winter months. They’re also unlikely to upset the balance of natural waterways, should they ‘escape’ your garden pond. It’s a good idea to have a mix of oxygenators if your pond is large enough. Plants can then be thinned out in spring, if necessary.
Check out some of the best plants to grow in garden ponds, below.
Spiked water milfoil (Myriophyllum spicatum)
This British native oxygenator has submerged olive green feathery foliage. Small yellow and red flowers appearing above the water surface between May and August. It suits all sizes of pond, as long as there is a minimum depth of 30cm and a max of 90cm. It’s easy to confuse with other non-native milfoils.
Fool’s watercress (Rorippa nasturtium-aquaticum)
This is a hardy British native that makes an excellent oxygenating plant. It produces foliage both above and below the water surface. In summer, the above-water stems bear small white flowers that are good for attracting bees, hoverflies and butterflies.
Hornwort (Ceratophyllum dermensum)
A common British native, this is a permanently submerged oxygenator. It’s best suited to a still water pond in sun or partial shade. The dark green feathery foliage floats in the water, growing loosely. Can be thinned out in summer. Leave the dark coloured stems and only take out the yellow or clear coloured ones.
Water crowfoot (Ranunculus aquatilis)
This is a British native oxygenator that is mostly submerged with some foliage appearing on the surface and white flowers in May. These will draw in the hoverflies, bees and butterflies. It will tolerate most water conditions including streams and rivers. It doesn’t generally require any maintenance.
Water moss (Fontinalis antipyretica)
This British native oxygenator grows deep under the surface of the water. The dark green branched stems and foliage will cope with still ponds or moving water and it will grow in sun or partial shade. It will spread, but can be easily managed by removing clumps by hand.
Slender club rush (Isolepis cernua)
Slender club rush, Isolepis cernua, is an evergreen annual or herbaceous perennial with a cosmopolitan distribution. It grows as a marginal aquatic plant, though can be grown in bog gardens and ponds in tubs, too. Creamy-white flowers dot the grassy foliage in summer.
Curled pondweed (Potamogeton crispus)
A very common choice, this submerged British native oxygenating plant has olive green, slightly seaweed-like foliage. It also produces small pinkish flowers above the surface in early summer. It grows equally well in sunny or partially shaded ponds and spreads easily. If it’s a new introduction to your pond, leave it to fill up to one third of the pond, then thin out older stems regularly to keep under control.
Water violet (Hottonia palustris)
This is a dual-pupose plant, functioning as a good oxygenator with pretty flowers above water. The foliage is attractive and feathery, with pinkish-violet primrose like flowers appearing above the water in May to June. It needs a minimum water depth of 60cm. Although it can be a little tricky to settle into a new pond at first, it will spread easily once it is happily established.
More oxygenators to grow
- Hair grass, Eleocharis acicularis
- British native mare’s tail, Hippuris vulgaris
- Goldfish weed, Lagarosiphon major