GROW: Keeping the water garden in balance

Apr. 13—The Oklahoma weather has been fluctuating between winter and spring, but warmer days are just ahead. That means it's a good time for gardeners to give their water gardens a spring tune-up.

A water garden is a fun element in the landscape and requires proper care to keep it in tip-top shape. Gardeners who are shopping for new water garden plants may want to consider lotus, cattail, canna lily, water lily, tiger lily, pickerelweed, swamp lily or corkscrew rush.

If the water garden doesn't have a lot of debris in the bottom, it doesn't necessarily need to be drained. Replacing the water will delay the developing balance of the pond's ecosystem. The algae that grow on the sides of the pond are beneficial and make the pond look more natural.

A second type of algae is the cause of the murky green appearance that ponds typically have in the spring. Algae bloom is common, so don't be alarmed if this occurs early in the spring. If the pond was in balance this past season, it should clear up as soon as the plants start to grow and use some of the excess nitrogen. The excess nitrogen is the cause of the algae bloom.

There are algaecides on the market, but that's a temporary solution to a problem only Mother Nature can fix. These products kill all the algae at one time instead of the slow, natural death rate that the pond ecosystem can handle. When this occurs, the microbial population of the pond begins a big degradation of the algae, and in doing so uses all the oxygen in the pond.

If you notice the pond turning green, single-celled algae are the problem. The long, filamentous algae that grow on the bottom and sides of the pond aren't responsible for this discoloration. These filamentous algae are good for the pond and aid in concealing the liners, shelves, pots and bricks used to prop up some pots.

Over time, the balance of the pond will shift away from the green algae, and the plants will cover most of the pond's surface. This will deny light to the algae. The oxygenators and other plants in the pond will eventually outcompete the algae for available carbon dioxide and soluble nutrients. Gardeners may experience a pond that suddenly clears overnight as the algae sink to the bottom.

Keeping the pond in balance isn't the only thing required for a water garden. Be sure to pull the pump and clean it regularly. Check the filters weekly. Also, make sure the edging is in good shape.

When the leaves and flowers of the aquatic plants die, remove them as soon as possible. Inspect plant roots to ensure they aren't damaged by fish and/or insects.

David Hillock is a consumer horticulturalist with Oklahoma State University Cooperative Extension.