(Editor's Note: This article was originally published on July 16, 2009. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)

Many water gardeners do not know that pond plants are divided into five categories based on their submersion depth and growth characteristics. For a healthy aquatic ecosystem, it is advisable to grow several plants from each category to expand oxygenation, filtration and of course beauty.

Level 1: Submerged with floating leaves

Level 1 plants are deeply submerged under water with roots that are held in the substrate or in pots at the lowest level of the pond while their leaves float on the surface to gather the sun's energy. Water lilies are the most common plant in this category, both tropical and hardy. Their tuber crowns grow anywhere from six inches to three feet below the surface and their leaves and flowers are held on or above the water's surface. Water lilies provide shade for both fish and to prevent algae in the pond, both important functions in a water garden. Tropical and hardy water lilies project their striking flowers above the surface of the water throughout the growing season and come in various colors.

Some popular Level 1 plants:

Hardy Water lilies

Perry's Baby Red

Colorado

Attraction

Tropical Water Lilies

Lindsey Woods

Red Flare

Star of Siam

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Level 2: Fully Submerged

Level 2 plants include all underwater oxygenators that are always submerged and do not need to grow above the water's surface. They can be anchored down in a pot with planting medium or float freely in the water. Level 2 plants are a vital part of any pond environment and provide extra oxygen for fish and inhabitants. Oxygenators also serve as an extra purification point in the pond, catching loose particles in the pond with their feathery leaves. In colder climates, oxygenators will have to be replaced every year but can be found at pet stores sold as aquarium plants.

Some popular Level 2 plants:

Anacharis

Hornwort

Cabomba

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Level 3: Surface Floaters

Level 3 plants are an important part of all aquatic systems and add beauty to water gardens. The third category is all surface floating plants that drift through the water with their roots suspended in the water with no anchor or growing medium. As with level 2 plants, surface floaters will have to be replaced in colder climates every year, but expand quickly and are important for providing shade and filtration for the pond.

Some popular Level 3 plants:

Water Lettuce

Parrot's Feather

Water Hyacinth

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Level 4: Marginals

Level 4 plants are plants that are submerged below the surface of water three to six inches. These plants can be potted and their crown sunk to a shelf below the pond's surface. During winter in colder climates, level four plants need to be dropped to the lowest level of the pond so that their crowns do not freeze, but the rest of the year their foliage and blooms rise above the water.

Many times Level 4 plants and Level 5 plants are interchangeable and can be grown at either level, such as umbrella palms and elephant ears.

Some popular Level 4 plants:

Corkscrew Rush

Pickerel Rush

Giant Spider Lily Crinum amabile

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Level 5: Bog Plants

Level 5 plants include all bog plants that like wet roots and can be situated in mud or constantly moist rocks. Bog plants serve as an expansion for the biological filtration of any water garden, helping to purify the water and harboring beneficial bacteria in their roots. Besides their roots, bog plants grow completely above the water's surface and add beautiful greenery and blooms to the outside edge of a water garden. Bogs can also exist alone without a pond as a landscaping feature or detached, but connected to a water garden as a biological filter.

Some popular Level 5 plants:

Sacred Water Lotus

Japanese Water Iris

Japanese Sweet Flag

Rain Lily

Umbrella Palm

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If you are missing one of these categories of plants in your pond, it might not be functioning as healthy as it could be. Many of these plants are easy to get your hands on - so keep shopping around online and locally. Enjoy your pond this summer!

Photos of 'Lindsey Woods,' Parrot Feather, Water Lettuce, and thumbnail belong to Susanne Talbert. The following belong to these DG members and can be found in the PF:

'Colorado' - victorgardener Rain lily - LilyChick Lotus - Wanda11'Red Flare' - LouAnn707Hornwort - bonitin'Frilled Enchantment' - shadowgirlUmbrella Palm - OkusAnacharis - Ginger749 Juncus - QCHammy Pickerel Rush - hankpageSpider Lily - JPreta