Before planting or adding plants it is a good idea to know your hardiness zone so your perennial plants don't turn into annual plants.
Click on this link and enter your zip code to find the U.S. Department of Agriculture zone number where you live:
Plants are a very valuable and important part of any water garden. They offer shade which helps keep the water temperature down and cuts down on light that algae needs to grow. They offer shelter to the fish in the pond, giving them a place to hide when they feel threatened. They absorb the nitrates in the water, helping the fish and the ecosystem. Marginal plants also add color and character to the pond. The plants mentioned here are winter hardy and can be left in the pond year round provided they do not get encased in ice in the winter. They will die back, but just like perennials they come back in the mid to late spring. Please remove all dead plant life. As the leaves and stems decay they serve as contaminates that will lead to poor health and death of pond life, they also look ugly.
Types of plants
Plants can be broken into 4 different categories: Floaters, deep water, marginals, and bog.
Floating plants help to absorb nitrates, shade the water and add oxygen into the water. They are excellent additions to ponds. Common varieties are: water hyacinth, water lettuce (pictured) and duckweed. These plants have roots that dangle in the water and absorb nutrients in the water. Some flower, most do not. If they appear to be shrinking or not doing well check the roots and wash off the sediments on them ( outside of the pond of course). Theses plants are not winter hardy and will die once the temperatures get below 40°.F
Deep water plants are put in pots and placed in the deeper parts of the pond. The hardy varieties include lotus, water poppy and hardy water lilly. There are tropical varieties of water lilies which bloom in the evening or during the day with rich reds and yellows, but they require the water temperature to be above 65°F or they die. Hardy water lilies have white, pink and yellow flowers that usually open during the heat of the day. Deep water plants can cover large areas of pond surfaces and are good choices for shading the pond water.
Marginal plants are found along the edge of a pond and add character to it. They prefer 2-10 inches of water give or take a few inches. Common forms of marginals include: Papyrus, horsetail, iris, arrowhead and cattails. Miniature cattails (pictured) are best for small to medium sized ponds (ponds less than 1000 gallons). They are usually potted to help control their spread.