Plastic, preformed ponds are simple to install, and come in almost every imaginable size and shape. While there are many benefits to installing a preformed pond, they look unnatural without pond plants to soften their hard edges and provide visual interest. Planting water plants in a plastic pond allows it to blend into the landscape. Adding a combination of floating, submerged and marginal plants provides a healthy environment for fish, drawing wildlife such as birds, dragonflies and butterflies to your backyard.
Plant marginal water plants (e.g., black taro, sweet flag, rushes or canna) in clay soil or pond muck in shallow containers on pond ledges or shelves. Raise the plants by inverting a clay pot on the ledge as a base. If the pond has no shelves, stack bricks on the bottom of the pond until the container sitting on top is submerged 6 inches above the container lip.
Tie submerged oxygenator plants together in bundles; hornwort is a good option. Wrap string around a brick and tie it to a plant bundle. Allow the brick to sink into the deepest area of the pond, away from any pumps or filters. Submerged plants do not need containers or soil.
Place floating leafed plants such as lilies in pond containers half-filled with pond soil or pond muck. Backfill the container with gravel to the crown of the plant, and submerge the container to a depth of 18 inches. Place bricks at the bottom of the pond to raise the plant.
Free-floating pond plants do not need any special planting care, but must be kept away from skimmers and filters, as their trailing roots will clog them. Pacific fairy fern provides good surface coverage and multiplies quickly.
Weigh containers down with gravel or rocks to keep fish from knocking them over or feeding on their roots. Large plastic strawberry containers make inexpensive pond planters.
Check with your local nursery before planting submerged oxygenators such as anacharis. Many are considered invasive species and are not allowed in ponds in certain states. Also check with your local nursery before planting free-floating plants such as water lettuce or water hyacinth, as they are considered invasive species in many areas.