Controlling Algae in Your Pond or Water Garden

Algae is present because the nutrients are available to support its growth. A small amount of algae is good for the aquatic garden since it absorbs excess nutrients in the water, helping to keep it pure. Uncontrolled algal growth depletes oxygen in the water and makes the water inhospitable for the fish.

Make sure that you have not overstocked your pond with fish. Also make sure that you are not overfeeding your fish. Uneaten food is source of nutrients that translates into algal growth, and a large population of fish produces a large amount of nutrients when they excrete waste products. A pond biofilter can help remove excess nutrients and keep the water clear. You can also add water to the pond periodically to dilute nutrients if you have an overflow system that can drain excess water out of the pond. Barley straw discourages the growth of certain types of algae. Pond supply firms sell barley straw products that can be submerged in your pond. Dyes are available that can be added to the water. The black material absorbs the sun's light energy and deprives the algae of the light it needs to carry out photosynthesis and survive. Dye products have the added advantages of protecting your fish from predators and concealing plumbing and pots in your pond.

Many aquatic plant gardeners are tempted to drain the pond, clean it, and start over with fresh water when confronted with algae. This is usually counterproductive since the excess nutrients that cause algae to grow build rapidly in the fresh water. Frequent water changes and cleaning can make for drastic changes in pond pH and are stressful for fish and other aquatic life. Only drain and clean your pond when a substantial layer of decaying organic matter has accumulated at the bottom.

Source:
U.S. National Arboretum

Choosing Plants for a Pond or Water Garden

When selecting plants for your pond, consider a mix of emergent, submergent, and floating species. Emergent plants, those that have their roots in the water but their shoots above water, can be added to the margins of pools. These include cattails (Typha spp.), arrowhead (Sagittaria spp.), and water lilies (Nymphaea spp.). Submergent species, or those that remain under water such as elodea, are often used as oxygenators. These are plants that remove carbon dioxide from the water and add oxygen. These plants are essential in most ponds to keep the water clear. Floating species or those that are not anchored at all in the pond include plants such as duckweed (Lemna minor), water lettuce (Pistia stratiotes), and water hyacinth (Eichhornia crassipes). While attractive, water hyacinth and water lettuce can be serious weed problems in the south; however, since they are not winter hardy, there is no problem with them spreading in northern climates. While not as effective as oxygenators, these plants help keep the water clear by limiting the amount of sunlight that algae receive. In tiny ponds created in barrels and similar containers, these plants may be adequate to maintain clear water.

Consider the following factors when selecting and establishing plants in your pond or water garden:

1. How deep is the water? This will be a factor in establishing plants and their survival over winter if you live in colder regions. Some species need a minimum depth of 2 to 3 feet to grow well.

2. Is your pond permanently installed in the ground or is it a small tub that will be moved inside in the winter? In this case, even tropical plants may be an option.

3. Will you drain your pond in the winter? If you intend to drain your pond, you should consider plants that can spend the winter in a basement in a dormant state.

4. How much sunlight does your pond receive?

5. How large is your pond? If your pond is small, consider dwarf species.

6. Purchase plants from a reliable vendor. Remember to include some oxygenator plants such as elodea.

7. Emergent and submergent plants should be planted into pots. A wide assortment of pots is available, from plastic baskets to pulp planters. Choose pots that are large enough for your plants.

8. If using baskets with numerous perforations, line the basket with burlap or 2 layers of newspaper to keep the soil from falling out of the holes.

9. Fill the container about half full with a mixture of good garden topsoil. Do not use potting mixes or peat moss. These are too light and will float out of the pot. Adding aquatic plant fertilizer to this bottom layer of soil is recommended for some species. Follow directions on the label for amount.

10. Place the plant on top of the soil and fill the container with topsoil within one inch of the top.

11. When planting water lily rhizomes, make a mound of soil in the middle of the pot. Place the rhizome at a 45 degree angle. The crown of the rhizome should be toward the center of the pot. Cover the roots with soil, but not the crown.

12. In all cases, add a layer of gravel to the top of the pot. This will help keep the soil from floating out and prevent fish from digging in the soil.

13. Slowly place the pots in the pool to keep soil from floating out. Place pots on bricks to get the desired height.

14. Floating species can be placed directly into the pond with no other care needed.

Plants should cover 50 to 70 percent of the water surface. Native plants usually do not need fertilizer. For some exotic water lilies, limited fertilizing once yearly may be required. Check with your nursery on care of plants and how deep to place potted plants. Be aware that overfertilizing may cause unwanted algae blooms which can rob the water of oxygen.

Source:
U.S. Department of Agriculture

Yellow Pond-Lily

Nuphar lutea


Alternate Names

Brandy-bottle, bullhead lily, Nuphar variegatum, spatterdock, yellow cowlily.

Nuphar lutea is divided into many subspecies. Comparisons of morphological features and interpretations of molecular analysis indicate the name Nuphar lutea should not be used for any North American Nuphar members. The genus Nuphar is now represented by eight distinct species in North America. A key to this new classification is provided in Flora of North America, volume 3, by Kartesz (1997) and Aquatic and Wetland Plants of Northeastern North America, volume 1, by Crow and Hellquist (2000).

Description

General: Water Lily Family (Nymphaeaceae). Yellow pond-lily is an aquatic perennial that grows to be 15 to 60 cm in height and spreads 1 to 2 m on the water surface. Spongy rhizomes anchor into the muddy bottom of a water body and give rise to long, stout stems. Submerged leaves are thin and attached to the rhizomes. Floating leaves are thick, somewhat heart-shaped, wavy along the margins, have up to a 40 cm spread, and are attached to the stems. Flowers emerge on separate stem stalks. They are cup-shaped, yellow-green, with small scale-like petals and numberous stamens and stigmas hidden within the thick showy sepals. Flowers bloom from May to October, partially opening in the morning and closing at night. Spent flowers give way to seed heads that burst upon ripening, broadcasting their seeds over the water surface. Flowers and leaf stems die back to the rhizome in autumn.

Yellow pond-lily may be confused with water lily, Nymphaea species, which have rounder leaves and showier pink to white flowers.

Uses

Ethnobotanic: Native Americans consumed the starchy rootstocks as boiled or roasted vegetables and harvested the seed for grinding into flour. There are some accounts of the root being powdered and used as a poultice.

Wildlife: Yellow pond-lily provides food and shelter for many fish and underwater insects.

Ornamental: Yellow pond-lily flowers and leaves are showy and fragrant. For this reason, it is used as an ornamental planting in water gardens and ponds.

Weediness

This plant may become weedy in some regions or habitats and may displace desirable vegetation if not properly managed. Please consult with your local NRCS Field Office, Cooperative Extension Service office, or state natural resource or agriculture department regarding its status and use. Weed information is also available from the PLANTS Web site at plants.usda.gov.

Distribution

Yellow pond-lily is native to the Eastern United States, Africa, Temperate Asia, the West Indies, and Europe. It is naturalized in most temperate regions of North America. It occurs in all 50 states except Hawaii.

Habitat

Yellow pond-lily occurs in slow-moving streams, still ponds, and lakes.

Adaptation

The USDA hardiness zones for yellow pond-lily are 4 to 10. It grows in wet, poor sandy soils and performs best in 1 to 3 feet of water in full sun to part shade. It is more tolerant of shade and deep water than Nymphaea species.

It is more often used in large water gardens and ponds where it can produce underwater stems that grow up to 2 m long and can slowly spread to form sizeable colonies.

Establishment

Yellow pond-lily should be grown in containers if they are used for water gardens. For natural ponds, plant rhizomes directly in the muddy bottom if naturalization is desired.

Seeds and Plant Production

Seeds are produced and deposited on the water surface, where they are carried to a germination spot. Yellow pond-lily reproduces more readily by spreading rhizomes.

Control

Although this plant is not considered invasive, it is very difficult to eradicate when not grown in containers because any section of rhizome left behind may sprout new growth.

Please contact your local agricultural extension specialist or county weed specialist to learn what works best in your area and how to use it safely. Always read label and safety instructions for each control method.

Source:
USDA NRCS National Plants Data Center