A pond is a very beneficial feature to incorporate into a permaculture property. Water ecosystems are very productive and ponds provide an opportunity to increase both biodiversity and harvest species on your property. Ponds also store water and attract a variety of wildlife. To ensure a good variety of plant life, there are five main categories of plants for ponds to consider.
Rooted floating plants grow vertically, with their roots in the bed of the pond and their leaves and flowers growing towards the surface, and their leaves and flowers floating on it. Their primary stems don’t necessarily have to breach the surface of the pond, but they will rarely grow without being within 10 centimeters or so of the surface. This is because they love the sun and need lots of direct sunlight in order to grow and thrive. The leaves that do reach the surface can provide beneficial shade and protection for fish, while species that flower help attract insects to your pond, which, in turn, provide food for amphibians and fish. If you plant species that flower, you should ensure that you remove the flower heads when they die, as a large in crease in organic matter when the heads rot can cause problems with algal blooms. Chief among the rooted floating species commonly used in garden ponds are lilies and lotuses, although water poppies and water hawthorn may also be suitable.
As the name suggests, floating plants exist by floating on the surface of the pond. They do not need soil or any other material in which to anchor their roots. All of their nutritional needs are met by extracting nutrients from the water. (Ensuring your floating species of plants are healthy and thriving is another reason to ensure a bio-diverse pond, so they can access sufficient nutrients.) This extraction of nutrients not only helps the plants to grow (in conjunction to the large amount of direct sunlight they absorb by being entirely on the surface of the water), it also means that there are fewer excess nutrients in the water, which can encourage algae to grow. Algae in small concentrations can have a role to play in garden ponds, providing food for some species of wildlife, but its rapid rate of growth means that it can quickly become a problem, deoxygenating the water, meaning plants and animals can die from lack of this essential gas. By absorbing nutrients from the water, floating plants help keep algae under control and ensure the ecosystem of the pond works for all the inhabitants. Duckweed and water hyacinth are popular choices for floating plant species in a pond.
Submerged plants have all of their parts below the surface of the water. Their roots are anchored at the bottom of the pond, usually by planting in pots that are then submerged. Their leaves float in the water above but rarely breach the surface. The leaves of submerged plants are usually fern-like with lots of tendrils to increase their surface area. This is because they get the carbon dioxide they need from the water, rather than from the air. Like all plants, submerged species absorb carbon dioxide and release oxygen. They are, therefore, great additions to a pond to ensure that the water remains oxygenated, and thus making oxygen available for fish and other aquatic wildlife. They also absorb nutrients from the water as well, so that, like their floating cousins, they can aid in the control of algae. Controlling algae is a benefit for the fish that inhabit the pond, but the submerged plants also provide the fish with food, either from consumption of their leaves directly, or of the microscopic aquatic creatures that make their home in the leaves. Pondweed and hornwort are examples of submerged species of plant suitable for a pond.
Marginal plants can be planted directly into the soil around the margins of the pond, but will also grow if planted in pots that are then submerged at the borders of the pond. The roots remain underwater but the majority of the plant – its leaves and flowers – typically grows above the surface. These species prefer sedate water conditions and provide important shelter for fish and amphibians, protecting them from land predators that may stalk the banks of the pond. Rushes and certain species of iris fall into this category, while Vietnamese and aquatic mint offer marginal plants that can be harvested for the kitchen.
In any water feature, including ponds, one must always consider the edge. While marginal plants work within the water of the pond, you need to ensure that the ground surrounding the pond is planted as well. Some permaculturists say that all watercourses should be planted with vegetation along their banks (as opposed to the cleared riversides typical of much modern industrial agriculture. There are good reasons for this.
First of all, having plants along the edge of a watercourse increases the biodiversity of the location. Using indigenous plants suited to the conditions can initiate a more diverse ecosystem. This, I turn, will attract a greater variety of wildlife and insects, so ensuring a more stable ecosystem – as we know ecosystems gain strength from numbers of different species. Secondly, planting the edge of your pond will, as with larger bodies of water, help maintain the integrity of the banks. The plant roots help bind the soil, decreasing erosion by the water. Furthermore, plants on the edge of a pond provide shade and ground cover, reducing wind erosion and water evaporation from the soil, as well as providing a pleasingly soft and aesthetic border to the pond. Ideally you want a variety of species around the ponds edge, with differing heights and ground cover, to enact all these benefits.
By ensuring that you have a good range of plant species in your pond, providing a variety of functions to the ecosystem, you can ensure that your water feature remains healthy, diverse and, importantly, a pleasure to sit beside and watch.