Water Lettuce & Floating Plants for Koi Ponds
Growing plants in your koi pond provide fish with shelter from the sun and a place to hide in the event of a predator. Plants also give ponds a lush, natural feel and can be used to landscape a garden or yard, adding colorful foliage. Some floating water plants also double as fish food, providing an easy snack for koi.
A floating plant, water lettuce (Pistia stratiotes) has thick green leaves covered in fine hairs. The plant's leaves cluster together in rosettes resembling heads of lettuce that vary from 2 to 18 inches in diameter. If left unchecked, water lettuce will grow out of control and take over other species of plant life. Koi take shelter in the long roots of water lettuce and under its leaves, though they may also consume the plants. Also, water lettuce naturally removes algae from ponds.
Koi love to snack on the small, fuzzy leaves of fairy moss (Carolina azolla). Floating on the water's surface, clusters of fairy moss also provide koi with shade, and the plant naturally reduces algae. In autumn, the green foliage of fairy moss turns a vivid reddish-purple and dies off, sinking to the bottom of the pond in the event of a frost or a hard freeze, according to the Minnesota Water Garden Society. In the spring, fairy moss will resurface.
Water soldier plants (Stratiotes aloides) have long green blades, so they resemble floating pineapple tops. Over time, the plant's leaves accumulate high levels of calcium carbonate, which causes them to sink beneath the water in winter. When new leaves develop in spring, they are free of calcium carbonate and float to the surface of the pond. This natural cycle also protects the plant from freezing temperatures. Be careful with water soldiers though, as they can quickly grow out of control and overtake a pond, though they do provide koi with shade and shelter.
Four Leaf Water Clover
Named for their resemblance to common clover, the four leaf water clover (Marsilea mutica) provides dense coverage and shade in koi ponds. Individual clover heads are roughly 2 inches wide and grow in clusters. The plant has long roots that sink to the bottom of ponds, or you can grow them in pots or between rocks. Like other floating plants, the four leaf water clover reduces algae by depriving it of nutrients and sunshine.
Exercise caution when choosing water plants in California, as some types are banned in the state to prevent them from doing harm if they escape into the wild. Some non-native plants damage local species of plant life if placed in natural waterways and others breed with native plants, creating troublesome hybrids. Always check the information provided by the California Invasive Plant Council at Cal-ipc.org to ensure the plants in your koi pond are legal and safe.
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