Water Plant Selection, Implementation and Maintenance
Whether you are planning to install plants at the edge of a naturally occurring body of water or at the edge of a newly created artificial pond, proper plant selection is key to success. After installing the hardscape of your pond*, it is time to establish the softscape (plant materials). The softscape creates a pleasant appearance, but also helps create a balanced ecosystem to keep the pond healthy as well as beautiful. The plant installation and maintenance for both types of water features will be discussed separately.
Plantings Suitable for Artificial Ponds
- Containers -- plastic with no holes is recommended 3-5 gallon for lilies 1-5 gallon for marginal plants 1 gallon for submerged plants
- Well balanced garden fertilizer; 12-12-12, 5-3-1, 7-12-5
- Fertilizer tablets
- Cement blocks -- size depends on the depth of pond and type of plant
- Heavy clay loam
- Pea gravel
Most water plants do well in direct sunlight. Consider also the exposure to winter wind and the depth of ice that accumulates over winter. When selecting plants, keep in mind the hardiness zone factor. Ponds have varying water movement, from no moving water to swift moving water. Plants need to be chosen that will thrive in the existing water conditions.
Plant Selection Process:
There are five categories of water plants that can be included in a pond to achieve perfect balance. Water lilies and lily-like aquatics, marginal plants, bog or moisture-loving plants, submerged or oxygenating plants and floating plants are the five categories.
Adapted from Water in the Garden by James Allison
- Water Lilies and Lily-like Aquatics: These grow on the base of the pond and send up leaves and blooms to the surface. Depending on the variety, they may grow a couple of inches to a few feet below the surface of the water. They provide valuable leaf cover to help shade the water, which reduces algae growth. Fish love to hide under the leaves too. Lilies do not do well with strong water movement or splashing water. Most species need full sun 10 hours a day for best blooms. A pond should have approximately one lily for every 5-10 square feet of pond surface. There are many different colors and styles of lilies. Here is a list of species in each color.
'Gladstone' has a white blossom and a slight fragrance. Leaves are green with red-striped stems. Plants spread to cover an area from 4 to 8 feet. This plant is best for large pools and should be grown in water 1 to 3 feet deep.
'Charlene Strawn' has a yellow, star-shaped blossom. It is very fragrant and is easy to propagate. The blossom opens in late morning and closes in mid-afternoon.
'Fabiola' has a pink blossom with slight fragrance. It has small green leaves and produces flowers very early and late in the season. It works well in small ponds because of compact size.
'James Brydon' has a rosy red blossom. The leaves are bronze-purple to dark green. It blooms later in the season. It grows well in pools that are shaded.
'Comanche' opens as a peachy yellow and matures to a coppery orange. Young leaves are purplish, and mature leaves are green with maroon speckles. It works well in medium-sized to large pools.
- Marginal Plants: These grow in the shallow margins around the edge of the pond. It is helpful if a shelf is incorporated in the pond design to support them. Marginal plants can be decorative, provide shelter from the wind, and offer a bit of shade. These plants do best in still to slow moving water.
Cattails are traditional aquatic plants. They have long narrow leaves and produce brown catkins. There are different species that grow from 3 to 7 feet tall. These can also be grown as bog plants.
Arrowhead produces white flowers with arrow-shaped leaves. It grows to about 2 feet tall.
Pickerel Rush produces spikes of purple, bluish or white flowers. It grows best in water 12 inches deep and enjoys full sun or partial shade.
- Bog or Moisture-loving Plants: These grow in damp soil at the edge of ponds and prefer to have only the tips of their roots submerged. They also do best in still to slow moving water. Start with a mixture of marginal plants and bog plants inhabiting about 1/3 of the circumference of the pond.
Horsetails form upright clumps of green stems. They have no leaves, and the tips of the stems have brown cones.
Iris are available in several different varieties. Iris most suited to a bog or moist environment are Japanese (Iris ensata), Yellow Flag (Iris pseudacorus), Siberian (Iris siberica), and Wild (Iris versicolor). They have slender upright leaves. The flower comes in a variety of colors (white, purple, red, etc.).
- Submerged or Oxygenating Plants: The roots of these plants are anchored in soil, but the leaves stay underwater. Their foliage is usually fern-like, lacy, or hairy. They play a vital role in maintaining the pond's natural balance. These plants use waste nutrients and help purify the water. This, in turn, creates an environment that is unsuitable for algal growth. They also provide cover for microscopic forms of life. It is best to include one bunch (these plants are sold by the 'bunch' or handful) for every two square feet of pond surface. Fewer bunches may be adequate once the natural balance is obtained. Grow a variety of species since each species grows at a different time of year and has different water depth requirements.
Anacharis is a deep green plant with many delicate leaves. It will grow in water 6 inches to 5 feet deep.
Vallisneria has ribbon-like, pale green leaves. It grows in water 6 to 24 inches deep.
- Floating Plants: These plants do not need soil or a base of any kind. As the name implies, they are simply suspended in the water. They provide decoration and shade and help reduce algal growth. One bunch is sufficient for every 10-15 square feet. These plants are vigorous growers and will need to be thinned periodically.
Water poppy is an example of a floating plant, but grows in zones 8 to 10. It can grow in zone 3 and 4 if you replace it each spring. It has yellow, 3-petalled flowers that rise above the floating foliage.
Place a small amount of water in the pond so the plants do not dry out. Have plants, containers, soil, sand, and pea gravel ready.
- Containers should be wider than deep because water plants have a shallow root system; it also keeps the container from tipping over. Plastic is the best material to use because it is lightweight. The containers should be dark colored because they are not as visible through the water. Handles are a convenient way to move the containers, though they are not necessary. It is best if the containers do not have holes in them (holes allow loose soil to disperse and will cloud the water). Many types of containers can be used: dish pans, buckets, clay pots or special containers from garden shops.
Desirably shaped shallow plastic planting containers.
Adapted from Garden Pools and Fountains by Ortho Books
- Heavy clay garden soil is best for most plants. Do not use manure or over fertilize, which may lead to water eutrophication (excessive nutrients and decreased amounts of oxygen).
The best time to move most water plants is during their growing season, from late spring until the end of summer. Containerized plants can be moved while dormant and placed in the pond. The best time to move submerged plants is spring or fall. Do not purchase the plants until you are ready to plant because you do not want them to dry out.
- Water Lilies: The hardy lilies grow from rhizomes. They are best grown in soil-filled containers set in the pond. Lilies can be introduced to the pond from spring to early fall.
- Mix a well-balanced garden fertilizer into the soil at the bottom of the container so it does not leach into the water, yet feeds the lily roots (about 1/2 cup of fertilizer for eight quarts of soil).
- Bury fertilizer tablets towards the bottom of the container.
- Fill the container half full of soil.
- Position the lily and gently add soil around the roots. Be sure to leave the crown uncovered.
- Spread 1/4 - 1/2 inch layer of pea gravel over the top to hold soil in place (again, be sure the crown is just above soil and gravel line).
- Position the lily container on cinder blocks in the bottom of the pool. In most cases the crown should be 6-18 inches below the water line. Check the needs of your particular lily to be sure.
- Bog and Marginal Plants: Similar planting techniques and care are given to Bog plants and Marginal plants.
- Fill the container about half full of soil.
- Place the roots of the plant in the soil and continue to fill. Be sure not to plant it too deep. You may want to place 3 plants in one container for a more full look. Keep different species in separate containers, for one species may overwhelm another species.
- Add one fertilizer tablet.
- Place the container at the edge of pond or on bricks in the pond. The container rims should be 2-4 inches below the water line.
- Submerged or Oxygenating Plants: These plants require a lot less soil than the bog plants and lilies. The soil will have a high proportion of sand and gravel. These plants do not require fertilization because they get their nutrients from the dissolved minerals in the pond water. It is good to plant these in containers because they may grow rapidly and become invasive if planted on the pond bottom.
- Plant about five or six bunches (with 6 stems/bunch) in a five-quart pail.
- Place containers in the pool so leaves are submerged to a depth of 6 to 16 inches.
- Floating Plants: No soil or containers are needed for these plants. The roots hang in the water while the leaves stay above the water.
- Throw a bunch on the water surface and they care for themselves.
Your pond may look bare at first, but after a couple of months the plants will mature and flourish. If your pond water becomes murky and fills with algae, do not change the water. Give the pond time to reach its balance. You may need to add more submerged plants at this time.
- Water Lilies: They should be fertilized regularly with one slow release tablet per eight quarts of soil every month during the growing season. Just press a tablet into the soil near the roots. Also remove any yellow or brown leaves, and old blossoms. This helps promote new growth and keeps the pond clean. Remove all the dead vegetation in the fall so the lily can start new in the spring. The hardy varieties thrive in cold areas and need not be removed from ponds as long as the water does not freeze down to the rootstock. It may be necessary to move the container to the bottom of the pool to be sure the lily roots are below the ice freezing level. Be sure to remove the lilies if the pond freezes solid.
For plants that need to be removed:
- Allow water to drain from soil then trim away foliage.
- Wrap container in moist burlap or peat moss.
- Store plant in a cool corner of a basement or garage (40-55 degrees F)
- Cover with plastic garbage bag to keep in moisture.
- Check regularly and water periodically to keep moist.
- Bog and Marginal Plants: Additional fertilizer tablets should be added when the plants are blooming. You may need to divide and thin the population in one container every one to 3 years.
- Submerged: Thin if necessary.
- Floating: If they reproduce too quickly, pull them out by hand or with a net. Depending on the species you choose and the type of winter you get, you may need to treat these as annuals and replace each spring.
Using aquatic plants on property bordering natural bodies of water has many benefits. They include:
- Improving aesthetics of shoreline by creating a more natural waterfront look
- Anchoring soil to prevent erosion from upland runoff
- Acting as a wave breaker to prevent bank erosion from wave action and high water
- Working as a buffer zone to prevent pollution from entering pond or lake
- Providing wildlife habitat
- Reducing maintenance
Amounts, Specifications, and Supplies:
Using native plants will provide lower maintenance and better hardiness. Exotic plants must be used with great care to prevent undue competition with native species. Planting in the water can only be done using native plants. Some plants may be harvested from local lakes and wet areas with the property owner's permission. Before doing this, check with the Department of Natural Resources Division of Waters (in Minnesota call 651-296-4800) to learn of any restrictions and guidelines for collecting plants. Buying plants from a nursery that grows plants from hardy and local stock plants and seed helps maintain the existing genetic makeup of your area. Aquatic plant sources for those that cannot be found at a local nursery are listed in Hennepin Conservation District's publication Aquascaping: A Guide to Shoreline Landscaping.
Tools and Equipment:
- Shovel for large plants and loosening soil
- Hand spade for small plants
- Anchors for plants exposed to moving water -- mesh bags with stones, or fence or sod staples
Plant material choices will depend on:
- Amount of sun the site receives -- full sun, part sun, or shade (full sun is best for most aquatic plants)
- Moisture level -- moist soil occasionally covered with water, shallow water, or deep water
- Amount of water disturbance the site receives -- fast moving stream water, open water subject to wave action, or slow moving water in protected bay
- In Minnesota, contact the Department of Natural Resources Division of Waters (651-296-4800) to receive a permit for planting aquatic plants. This is a required permit and has no fee. Outside Minnesota, contact your state's DNR for regulations. Contact your local government office to learn of any permit requirements or applicable restrictions.
- Determine the soil type: sand, muck, or gravel. Determine the amount of sun the site will receive. Determine the amount of water movement, if any, the site will receive.
- Determine the type and number of plants to use. See reference list for sources of information on plant selection.
- Prepare the site by removing unwanted vegetation. If possible, remove by hand. Use herbicides only in areas that are not in or next to the water. Follow herbicide directions carefully. Allow ample time after herbicide application before replanting (see package instructions). Herbicide use in water requires a DNR permit.
- Soil amendment is not necessary if the proper plants are chosen for the site.
- Plant the plants as soon as possible after receiving them. Keep plants moist, and store in a cool environment until planted.
- If plant material is in a peat pot, plant the entire pot.
- In areas above the waterline, plant in small blocks to limit the amount of exposed soil.
- Place plants close together to leave as little soil exposed as possible.
- Use organic mulch over exposed soil to prevent erosion and keep the plants moist.
- If working in large areas, use straw bales or silt fences between the area you are working and the water to prevent soil erosion until the area is stabilized with plantings and organic mulch.
- On slopes, loosen the soil and incorporate organic mulch into the top two inches to prevent water from washing the mulch away.
- Roots and tubers should be planted at the same depth as they had previously been growing.
- Use mesh bags with stones, or 6-inch fence or sod staples to anchor roots of plants exposed to wave action.
Allison, James. 1991. Water in the Garden. Salamander Books Limited. London, England
Henderson, Carrol L., Dindorf, Carolyn J., Rozumalski, Fred J. n.p. Lakescaping for Wildlife and Water Quality. Minnesota's Bookstores. St. Paul, MN.
Hennepin County Conservation District. n.p. Aquascaping: A Guide to Shoreline Landscaping. Hennepin Conservation District. Minnetonka, MN.
Mills, Dick. 1992. A Popular Guide to Garden Ponds. Tetra Press. Morris Plains, N.J.
Minnesota Department of Natural Resources. 1997. A Guide to Aquatic Plants: Identification and Management. Minnesota Department of Natural Resources. St. Paul, MN.
Ortho Books. 1988. Garden Pools and Fountains. Chevron Chemical Company. San Ramon, CA.
Sacher, Rich. n.p. "Tropical Water Lilies." Custom Water Gardens.
Shoemake, L.J., Arnold, M.A., Welch, W.C. n.p. Texas A&M University, Horticulture and Extension Department. "Plant Life." Water Gardening in Texas. http://aggie-horticulture.tamu.edu/extension/homelandscape/watergarden/plant.html.
University of Wisconsin, Extension Service. n.p. "A Guide to Selecting Landscape Plants for Wisconsin." Madison, WI. Publication UWEX:A2865.
University of Wisconsin, Extension Service. n.p. "Nursery Sources for Natural Landscaping." Madison, WI. Publication UWEX: GWQ014A
University of Wisconsin, Extension Service. n.p. "Shoreline Plants and Landscaping." Madison, WI. Publication UWEX: GWQ014. http://cfpub.epa.gov/npstbx/files/wiexlandscape.pdf.
Water Garden. June 2000. "Planting and Caring for Aquatic Plants." http://watergarden.com/pages/plant_care.html.
Wieser, K.H. and Loiselle, Dr. P.V. 1988. Your Garden Pond. (3rd ed.). Tetra Sales. Morris Plains, N.J.
Wisconsin Department of Natural Resources. n.p. "Guide to Wisconsin Aquatic Plants." Wisconsin Department of Natural Resources. Madison, WI.
This implementation report was developed by Hilary Rossow and Darlene Charboneau, students, University of Minnesota Department of Horticultural Science.