A pond adds new dimension to the backyard and new challenges for many inexperienced with aquatic plants. A pond creates a ecosystem that requires more than topping it off with a hose and plunking in a couple of goldfish to avoid an algae-covered litter that needs constant maintenance. Pond plants create your water feature look more appealing and natural while they provide a habitat for fish and frogs and naturally filter the water. While you don’t need to be worried about watering pond plants, there are a couple of things to bear in mind when planting a pond that differ from planting a traditional garden.
Kinds of Aquatic Plants
There are 3 chief types of aquatic plants you can combine for a healthy pond: floaters, emergent and submergent plants. Floaters don’t require planting; they develop on the surface, drawing nutrients in the water. Pacific fairy fern (Azolla filiculoides) and cape pondweed (Aponogeton distachyon) are just two non-invasive floaters. Emergent plants may be “marginals,” meaning they develop around the edge of this pond from its border in around 6 inches of water — like clumping bamboo (Bambusa multiplex), Japanese iris (Iris ensata) and pickerel weed (Pontedaria cordata) — or floating emergents like waterlilies (Nymphaea spp.) And lotuses (Nulumbo lutea) that have their origins in the soil and foliage and blossoms around the surface. As their name suggests, submerged plants develop totally beneath the surface and help to oxygenate the water, especially important when your pond contains fish. Non-invasive submerged plants comprise waterweed (Elodea canadensis) and coontail (Ceratophyllum demersum). Many water plants are dangerous. Select plants carefully to avoid the ones that can spread outside your little pond to shake local waterways.
Pond Size
The size of your pond can limit planting choices. A shallow pond heats up easily — encouraging algae growth — also does not provide the depth some plants or fish need. A waterlily, for example, needs 18 to 24 inches of water to thrive, while marginal plants can develop in just a couple of inches. Ponds that have a small surface can only support a few crops. A pond without a pump or filter should be at least 18 inches deep with a surface size of 50 to 75 square feet. Otherwise it can’t support enough plants to maintain a natural balance between nutrients from the water and mineral uptake by plants — an imbalance contributes to excessive algae. A well-balanced pond has crops within 60 to 70 percent of its surface. Local building codes additionally impact pond depth; in certain communities a pond more than 18 inches deep is treated the same as a swimming pool and requires a safety fence.
Plant Requirements
Most aquatic plants need at least six hours of sunlight, so construct your pond in sunlight. Containers simplify planting even in a natural pond. Unlike most container plantings, soilless mixtures aren’t advised. Instead use soil straight out of the backyard or a mixture of equal parts garden soil and coarse sand with pea gravel. Fertilizer should not be overused as it can contribute to algae growth, but can be tucked in to pots as pills formulated for aquatic plants in planting time and monthly from spring to early summer. A coffee filter filled with 4 ounces of balanced granular fertilizer per cubic foot of soil in the container and secured with a twist tie functions nicely for binder waterlilies and lotuses. Use half that amount for emergent plants.
Planting Technique
You pot a aquatic plant as you want any above-ground specimen. Containers may be standard plastic pots or mesh pots specifically for aquatic plants. Waterlilies and lotuses offered as rhizomes need to be planted with the bud end angled upward toward the surface of the soil, just at or slightly below soil level. Waterlilies need pots 10 inches deep and 10 to 15 inches in diameter, while lotuses need large pots, around the size of a half barrel. Marginal and emergent plants need pots based on the size of the root ball and the dimension you want the plant to maintain — they will expand in their bud. Topping the soil with pea gravel keeps both soil and plant in place while roots establish. A set of a cinder block below the pot can adjust the plant to its favored thickness in a deeper pond.