Aquatic plants, often called hydrophytes, are uniquely adapted to live in water or in soil that is permanently saturated with moisture. They contribute significantly to the health and aesthetics of a water feature, transforming it into a balanced ecosystem. These plants absorb excess nutrients like nitrates and phosphates, which helps limit the growth of nuisance algae. They also provide essential oxygen for fish and other aquatic life during daylight hours. Plant life offers shelter and shade for pond inhabitants, while also stabilizing the pond’s edge to prevent erosion.
Understanding Aquatic Plant Types
Aquatic plants are grouped into categories based on their growing habit and placement within the water column. This classification determines the specific planting method required for their establishment. The three main types are marginal and bog plants, submerged and oxygenating species, and free-floating varieties.
Marginal and bog plants root in wet soil along the pond’s edge, with foliage growing out of the water. Species like cattails and irises thrive in shallow water or moist soil found on pond shelves. Submerged plants, also known as oxygenators, live entirely beneath the water surface. They maintain water quality and clarity by drawing nutrients directly from the water through their leaves. Floating plants rest on the water’s surface, with roots dangling freely without needing any substrate.
Planting Marginal and Bog Species
Planting marginal and bog plants requires securing the roots in a container designed for aquatic use, such as a slotted aquatic basket or fabric planting bag. These containers allow water circulation while keeping the planting media contained. Use a heavy clay garden soil or a proprietary aquatic planting mix. Standard potting soil must be avoided because its light, organic composition causes it to float and decompose, fouling the pond water.
Before planting, tangled roots should be gently trimmed back. The plant’s crown—where the stem meets the roots—must be positioned at or just below the soil surface. After firming the soil, cover the container media surface with a layer of clean pea gravel or small pebbles. This layer prevents the soil from washing out and deters fish from disturbing the roots. The container is then placed on a shallow ledge or shelf, with the water level positioned just above the container rim to keep the soil saturated.
Anchoring Submerged and Oxygenating Species
Submerged plants, such as anacharis or hornwort, are often sold as unrooted stem cuttings bundled together. These bundles can be anchored directly to the pond bottom using a weighted material, such as a lead plant weight or non-toxic stones secured with a rubber band. This method allows the plant to remain submerged, where the stems will naturally form roots and anchor themselves into the substrate or gravel over time. This approach is simple for quickly introducing oxygenators.
Alternatively, rooted varieties or stem cuttings can be planted in small, deep containers. Fill these containers with heavy clay-based soil, similar to marginal plants, and top with a layer of gravel to prevent dislodging. Once potted, submerge the plants deep enough to ensure they are entirely underwater, but not so deep that light penetration is limited. A depth of 1 to 3 feet is often sufficient to allow access to sunlight while protecting them from strong surface currents.
Placement and Care of Floating Species
Floating aquatic plants, including water hyacinth and water lettuce, do not require planting into a substrate. Introduce them by placing them gently onto the water’s surface. If the plants appear dry upon arrival, they benefit from a brief acclimation period in a shaded area for two to three days to allow them to re-hydrate before moving to full sun. These plants absorb necessary nutrients directly from the water through their dangling root systems.
The primary management concern for floating plants is their prolific growth rate, which can quickly cover the pond surface. Thin them out regularly, aiming to maintain 30 to 50 percent surface coverage. This controlled coverage provides beneficial shade and nutrient absorption without blocking light to submerged plants or hindering gas exchange. Floating plants should be positioned away from strong currents created by waterfalls or skimmers, which can cause them to congregate and clog filtration systems.