Can I grow any canna in my pool?
Cannas are native to moist areas and many do quite well if grown in water, as
long as they are not submerged too deeply. The cannas in the pool at the
U.S. National Arboretum are varieties of Canna glauca or hybrids
between Canna glauca and other canna species. They may also be grown
in bog plantings where the soil is constantly saturated. Garden cannas
are surprisingly adaptable to wet conditions and some may be grown in water
if temperatures are warm. The rhizomes of all cannas rot in cold, saturated
soil, so they cannot live over the winter in the aquatic garden.
Can I keep my plants in the pond during the winter?
That depends on which plants you are growing. Some aquatic plants
are perfectly hardy and can spend the winter in the pond. Hardy water
lilies and lotus can simply be moved to a lower depth in the pond.
Hardy plants such as cattails, water iris, and rushes can stay near the
water's surface where they normally grow. Tropical plants such as
tropical water lilies, cannas, and papyrus cannot even tolerate cold water,
so they must be kept in a greenhouse over the winter or they must be started
from new divisions every year.
What can I do to keep algae out of my pond?
The algae is growing 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.
Should I put fish in my pond?
Fish add movement and character to any pond, and they are an important component in a healthy aquatic ecosystem. They also eliminate mosquitoes and other insects that breed in water. Many fish species also eat aquatic plants, however, so it is important to keep their numbers at a reasonable level. Many aquatic gardeners keep ornamental carp known as koi in their ponds. These fish are available in a myriad of colors and patterns and can live for a very long time and grow quite large. Goldfish are very adaptable and can survive the winter in your pond if it does not freeze to the bottom and a portion of the water surface is kept free of ice to allow for gas exchange.
If you choose to keep fish in your pond, make sure they don't have the
opportunity to escape to natural waterways in your neighborhood where they
can compete with and displace native fish species.
Where can I get more information about aquatic plants and koi?
For more information about Victoria Water Platters at the U.S. National Arboretum, visit our "From Seed to Autumn Gala and Beyond: Victoria Water Platters at the U.S. National Arboretum" page.
For more information about water gardening, visit the International Waterlily and Water Gardening Society at www.iwgs.org. It's also worthwhile to use your favorite search engine to search for nurseries specializing in plants for water gardens.
For more information on koi, visit the Associated Koi Clubs of America web site at www.akca.org or the Zen Nippon Airinkai at www.anabuki.co.jp/zna/english.
If you're interested in Victoria water lilies, you can find more information at www.mobot.org/MOBOT/hort/lily.
If you want some tips on finding sources for water lilies and other plants for the aquatic garden, check the Plant Sources Page
Back to the Arboretum Home Page
Last Updated March 4, 2004 9:12 AM
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