No matter how well-balanced a pond habitat, it can always use a few flowers. Flowers brighten dark spaces and punctuate green foliage. They provide lures for insects that bring koi and other ornamental fish to the surface. Best of all, ponds provide natural habitats for specialized plants that are difficult, or impossible, to grow elsewhere in the garden, which expands plant choices for backyard gardeners.
Water flowers are the serene royalty of the water garden. They grow from rhizomes or tubers anchored in soil and leaf out and bloom on the water's surface. Unlike surface plants, whose respiration occurs on the underside of the leaf, water lilies and other floating flowers "breathe" through "stomata" on the tops of leaves. For this reason, water lilies and lotus, as well as most other water flowers, are planted in still water to keep leaf-tops in open air. Floating plants come in colors ranging from reds through yellows and whites. Water lilies (Nymphaea) may be annual or perennial and come in shades of purple, red, pink, peach, yellow and white. Hardy water lilies bloom during daylight only but tender tropical daylilies will bloom either during the day or at night; some stand above the water's surface. Another popular water flower, the lotus (Nelumbo) is a close relative of the water lily and comes in shades of pinks, yellows and white. Although it is trickier to start and requires full sun, it can overpopulate quickly and requires large pond areas to thrive. Other popular water flowers are orange snowflake (Nymphoides hydrocariodes), water poppy (Hydrocleys nymphoides) and aquatic jenny (Lysimachia nummularia).
Bog and Marsh Flowers
These flowers grow in shallow water and saturated soil. If you have a natural pond, you may want to consider plants like brilliant red cardinal flower (Lobelia cardinalis) or white or purple pickerel rush (Pontederia cordata). Each can be planted at water's edge or in shallow water. Hanashōbu Japanese irises typically grow in wet land. Some bog or marsh flowers, like bog bean (Memyanthus trifoliate) purple or white obedient plant (Physostegia virginiana) can become invasive and should be planted in containers to limit their growth. Some like the lovely purple loosestrife (lythrum salicaria), are so invasive that their culture has been outlawed in states where they are choking out native plants along waterways. They should not be planted in the home pond garden because of their potential for uncontrollable proliferation.
Pond-side flowers can be planted in soil around ponds. Many of these plants, like astilbes and cannas (Erebus), also grow well in the garden border. Some, like hibiscus and cardinal flower (Lobelia cardinalis), are successful bog or marsh plants; they make an impressive display on land along ponds, especially those with stream-like running water. Kakitsubata Japanese irises flourish at water's edge. Use yellow butterfly flowers or white swamp milkweed (Asclepias incarnate), yellow marsh marigold (Caltha palustris) and upright Blue Lobelia (Lobelia syphilitica) to fill pond-side areas. Most other garden flowers that require moist conditions will also do well pond side providing their roots do not end up sitting in water.