Maintaining plants for a small pond or fountain doesn't have to take a lot of work. Choose plants that can survive the winter and you won't have to worry about how to overwinter those fussy tropicals. Most hardy plants will just need to be divided every few years.
Everyone loves water lilies, and hardy water lilies come in many sizes and flower colors. If you don't have space for a full-sized plant, try one of the many dwarf varieties available. Flower colors range from white to pale yellow to all shades of pink. Pickerelweed makes a great choice for medium to large water features. Its hyacinth-like blue flowers bloom throughout the summer. Duck potato, or wapato also grows rooted below the water. It's known for its edible tubers and delicate white flowers. These plants can be planted in ponds with water less than 18 inches deep or can be planted in pot that can be submerged in a water feature.
There are many choices of hardy plants that will grow at the edge of the water. These plants tolerate growing in a few inches of water or occasional flooding. Blue flag irises are easy to grow and their cheerful purple flowers bloom in early summer. The bright red summer-flowering cardinal flower attracts hummingbirds. Marsh marigold's buttercup-yellow flowers bloom in spring adorning these low-growing plants with their shiny, dark green leaves. As a foliage accent, sweet flag looks like a grass. Some varieties have variegated leaves. For more natural areas, try the large marsh mallow with its saucer-size red, white or pink flowers.
Grass-like sedges and rushes make great plants for water features as well. One of the most popular is the corkscrew rush with its curly stems (shown in picture). It likes to grow in several inches of water and will be evergreen throughout most of the Mid-Atlantic. Plant it in a submerged pot to keep it contained. Tussock sedge forms a soft mop of green that gradually sits higher as new leaves grow over the previous year's leaves.
Photo courtesy of the Missouri Botanical Garden Plantfinder
In selecting plants for your water feature, stay away from these invasive plants. Lesser celandine looks much like marsh marigold, but it will take over wetlands and floodplains. Yellowflag iris is a cousin of blue flag iris, but unwelcome in natural areas because of its rapid spread. The pretty purple flowers of purple loosestrife (shown in picture) may seem attractive, but this plant outcompetes native wetland plants and fills in open water habitats that waterfowl depend on.