There are four basic types of pond plants. For an attractive, well-balanced pond, we recommend using a mixture of all four plant groupings. A varied selection of plants has an impact on both the beauty of a pond and on the water quality.

• Marginals :

These plants grow in shallow water or saturated soil around the perimeter of ponds or along the banks of streams. They frame the water feature and soften the transition between land and water. They can also provide an attractive backdrop to small ponds. The largest selection of plants falls within this group. Their function in the pond is primarily ornamental. However, if you grow marginal plants in mesh baskets in a gravel or expanded clay media, their hungry roots will grow out of the container and pull nutrients directly from the pond water. If you plant these plants in gravel planting beds in the pond you will create natural bio-bogs to remove nutrients and boost the area that beneficial bacteria can colonize.

• Submerged Plants :

This group of plants grow beneath the surface of the water where most or all of the foliage remains. The name "oxygenators" is also used for them because they release oxygen into the water during the day. The primary function of these plants is to remove excess nutrients from the pond, thereby reducing the growth of algae. They also provide spawning areas and protective cover for fish. Typically these plants are grassy in form and are sold in tied bunches. Some of them are free floating like Hornwort (Ceratophyllum demersum). Others are hardier if they are potted in gravel such as Anacharis (Elodea densa), which will be killed if frozen in an ice layer at the surface of the pond during winter months.

• Floaters:

These plants float freely on the surface of the water. Floaters reduce algae by competing for nutrients, shading the water to cool it and lowering the light penetration. Most floaters are tropical and should be removed from the pond and composted prior to the onset of winter. The most popular floater is the Water Hyacinth (Eichhornia crassipes). This rapidly multiplying plant develops a strong trailing root system which removes excess nutrients and pollutants from the pond. Due to their natural filtering ability, they are commonly used for water purification at treatment plants in the southern states. Occasionally hyacinths will develop a lovely orchid-like flower. Other popular floaters are Water Lettuce (Pistia stratoides), Frogbit (Hydrocharis morsus-ranae) and the tiny floating plants, Duckweed (Lemna minor) and Azolla (Azolla sp.).

• Floating-Leaved Plants :

Everyone's favorite pond plant, the Water Lily, is in this group. These plants root on the bottom of the pond and send floating leaves up to the surface. We like to keep our lilies in pots or build planting beds right into the bottom of the pond. Lilies grow in water up to about 3 feet in depth. In the Pacific Northwest, with our cool nights which keep water temperatures down, we feel that most lilies are happiest at a depth of about 2 feet. At this depth the sunlight penetration is better and the water is warmer. There are also miniature lilies which can grow in as little as a foot of water, but they must be moved to deeper parts of the pond for winter protection. If ice is allowed to touch the top of the tuber a hardy Water Lily will die. The primary benefit of floating-leaved plants is the surface shade they offer