Also known as oxygenators, submerged pond plants live entirely underwater – almost. They do flower and the flowers will rise to the surface of the pond for pollination. However, most of these flowers are insignificant and don’t constitute the reason to purchase the plants. They act as a wonderful natural filter in your pond, consuming excess nutrients. Submerged plants for your pond include the familiar aquarium grasses such as elodea, anacharis, hornwort, foxtail, cabomba, and vallisneria.
For the most part, submerged plants take their nutrients directly from the water, which means they compete with algae for their dinner. Algae are nothing more than single-celled, green aquatic plants. Being bigger, more voracious, and better-looking than algae, submerged pond plants usually end up with most of the food, thereby starving the algae to death. So if algae control is top on your list for maintaining your pond, you’ll want to add a few oxygenators to the water garden.
Another great function that submerged aquatic plants serve is providing areas for fish to spawn and baby fish (fry) to hide.
Purchasing and Planting
When purchasing submerged plants, you’ll find they are usually sold in bunches of stem cuttings and are available weighted or unweighted. Weighted bunches have a weight tied to the bunch that helps keep the plant in place at the bottom of the pond. If you’re unable to find weighted plants, simply tuck their ends under a rock to keep them from traveling and floating into your skimmer.
Weighted bunches can be tossed into your pond. Unweighted plants can be planted in an aquatic plant pot with gravel, sand, or potting media. You can also plant them directly into the substrate of the pond. Most submerged pond plants prefer water that is 24 to 36 inches deep, except for hornwort which floats near the surface of the water. If you want to overwinter hornwort, simply place a stone on the floating mass to hold the plant below the ice layer of the pond.
Types of Submerged Pond Plants
Just like with marginals and waterlilies, some pond owners have their favorite submerged plants. Here are four of the more popular varieties that are all native to North America.
Anacharis – Egeria densa
Anacharis is the most popular of the submerged plants. It grows rooted in pond substrate or potted in sand or pond plant media. It has tiny white flowers that develop on the surface of the water in the summer. Each stem has short, thin leaves whorled around it, like a bottle brush, and can grow up to six feet in length. Hardy in Zones 5-11.
Hornwort – Ceratophyllum demersum
Hornwort grows as a dense, rootless mass that floats below the surface of the pond. It has very small white flowers in the summer that often look like pollen floating on the surface. Keep these wanderers in place by weighting them with a rock. Hardy in Zones 5-11.
Cabomba – Cabomba caroliniana
Cabomba lays completely flat when growing out of the water but produces a beautiful fan when submerged under water. The tops of the finely cut leaves are dark green and the underside is dark red. Cabomba bears small white flowers in summer. The fronds of cabomba are softer than hornwort, and therefore, more agreeable to pond fish. Hardy in Zones 5-11.
Eel Grass – Vallisneria americana
Eel grass has long, eel-like leaves that grow from a rooted runner planted in the pond substrate or in a pot with pond plant media. It grows 24 to 36 inches long and forms a thick mat across the bottom of the pond. There are many varieties of eel grass, each with different growing habits such as a corkscrew form and some that have red foliage. Hardy in Zones 4-11.
Maintenance and Care
Submerged pond plants can grow rapidly and will need to be thinned out from time to time. Simply toss the removed plants into your compost pile.
Submerged plants contribute to the overall health and beauty of the pond, acting as natural water purifiers. Be sure to add a few of these beneficial plants and enjoy their flowing appearance and algae-fighting qualities.