by Kerri Bailey, revised 3/20/18
Water or aquatic plants are essential features for any pond or water garden. They add beauty and color softening the rocks, while providing shelter for fish. The bonus is that they also help keep your water clear and fish healthy. Water plants also compete with algae for nutrients and consume excess fish waste. So you may want to add more plants to your pond to increase your filtration and pond appeal.
What are Water Plants?
So, what are water plants? They range from plants that tolerate wet feet and areas to plants that can be completely submerged in water. These plants can survive and thrive in wet areas year round (or naturally for their life cycle). Many common garden plants can be used in ponds or bogs that grown along the edges (margins) and stream areas. When plants are grown in water, they produce a different type of roots than soil grown plants. Aquatic roots are long and filamentous with feathery looking root hairs. These roots grow into the water for searching for nutrients, oxygen and are used to anchor themselves. Some plants float on the waters surface that have air bladders inside their leaves or stems to keep them buoyant with roots that grow completely submerged.
Water Plant Groups
Water plants are classified into four main groups: “Water Lilies and Lily-Like”, Marginals, Floaters and Submerged plants. Each plant group is dependent upon where they grow in the pond or how deep they can be submerged in water.
Water Lilies are the jewels of the pond. The root or rhizome grows in deep water (1′-4′) with stems that grow upward toward the water surface. Leaves and flowers float on the water surface or slightly above. Water lilies are divided into two types- Hardy and Tropical. Hardy Water Lilies are hardy from zones 3-9 and can be grown just about anywhere in the country year round. They typically are day bloomers that are available in many colors with leaves and flowers that float on the waters surface. Tropical Water Lilies need warmer temperatures (above 65ºF) and are usually treated as annuals or winterized inside. They come in vibrant bloom colors with leaves and flowers that stand out above the waters surface. They are either day or night blooming. Check your zone at: http://planthardiness.ars.usda.gov/
Lily-Like Aquatics Grow similarly to hardy water lilies but have smaller leaves and flowers, and grow in shallower water depths. They are very versatile working well in containers and in small ponds. The lily-likes vary in leaf size and shape, temperature hardiness and flower form.
Marginal Plants A very large group of plants that grow on the margins of ponds, bogs or stream edges. They are grouped as hardy or tropical- hardy plants survive below zone 9 and tropicals survive above zone 9. Iris & Cattails are hardy marginals and Taro & Papyrus are tropical marginals. Some marginals can survive in wet soil to a few inches of water depth, and others can grow deeper (up to a foot of water).
Floating Plants or Floaters Plants that float on the waters surface with their roots submerged into the water. Their leaves have air bladders that keep them buoyant. Most are annuals ( Water Hyacinths, Water Lettuce) some are hardy (Azolla, Frogbit)
Submerged Plants What most people think of as “water weeds”.
They are often referred to as “oxygenators” which is misleading, as all water plants consume and produce oxygen. These plants are found under the water surface either freely floating or anchoring themselves to the bottom. At times they may grow at the waters surface or out of the water. Most have insignificant flowers, others have delicate blooms. Many are considered “noxious weeds” so check the list to see what you can grow in your state http://plants.usda.gov/java/noxious?rptType=Federal
WA State see: http://www.nwcb.wa.gov/ab_weedlaw.htm
Kerri Bailey, owner of The Pond Pad, has been working with aquatic plants and herbs since 1989 and has been in the pond and horticulture industry since 1998. She has a BS in Biology and is a Certified Herbalist.