Can You Have Plants in Your Koi Pond?

Koi rise to the surface at feeding time.

Koi rise to the surface at feeding time.

A rising koi spreads ripples across the water's surface, gently rocking the fairy fern floating in the middle of the pond. A healthy koi pond generally incorporates both koi and a variety of plants to provide a balanced aquatic system. Native to Japan, koi are omnivores and enjoy eating the leaves and roots of your pond plants. With careful planning, you can enjoy your beautiful water plants and still raise koi in your garden pond. Most aquatic plants require six or more hours of sunlight daily to thrive.

Benefits of Plants

Aquatic plants provide significant benefits to a koi pond. The plants use the koi's wastes as nutrients, add oxygen to the water and hide the koi from predators such as cats, raccoons, egrets and cranes. Plants also shade the water, cooling it on hot days. In addition, the plants compete with algae for nutrients, reducing the amount of green algae growing in the pond.

Bog Plants

Whenever possible, use native bog plants, such as cardinal flower (Lobelia cardinalis), common yellow monkeyflower (Mimulus guttatus), pickerel weed (Pontedaria cordata) and western blue flag iris (Iris missouriensis), around the perimeter and in the shallowest parts of the pond. Sink the pots so the rims are barely below the surface of the water, or in the muddy soil around the perimeter of the pond. If the koi have access to the pots, use large rocks to cover the soil and prevent fish from eating the plants' roots.

Floating Plants

Floating pond plants conceal the koi and provide shade over the pond. No pots or soil are necessary, these plants float freely on the water's surface. The koi happily eat the leaves of most floating plants, including the Pacific mosquito fern or fairy fern (Azolla filiculoides), watershield (Brasenia schreberi) and water clover (Marsilea spp.).

Lilies and Lotus

The floating leaves and nodding flowers of the hardy water lilies (Nymphaea ssp.) and lotus (Nelumbo ssp.) provide additional coverage over the surface of the pond. Both lilies and lotus are grown from tubers. Once the plant is established in a plastic tub, the 18- to 24-inch tub is sunk into pond. Lotus are submerged up to 6 inches below the surface of the water, while hardy lilies thrive in water between 6 and 24 inches over the top of the pot. Place large stones over the soil to prevent the koi from rooting out the tuber and eating it.

Submerged Plants

The submerged aquatic plants provide additional oxygen to the water. At times you can even see the bubbles rising from the leaves. While many varieties of submerged plants are quite prolific, the koi eat them nearly as quickly as the leaves emerge. The recommended native varieties include coontail (Ceratophyllum demersum), water smartweed (Polygonum amphibium var. stipulaceum) and waterweed (Elodea canadensis).

Avoid Invasive Varieties

While your pond may be several miles from the nearest river, estuary or wetland, avoid using invasive aquatic plants in your koi pond. Water flowing into a storm drain, a predator carrying off a koi along with a snippet of a plant or a winter flood may accidentally spread invasive species to a nearby drainage or creek. Once established in the wild, invasive aquatic plants are extremely difficult to control, costing your state millions of dollars in attempts to eradicate them from waterways. The California Invasive Plant Council warns water gardeners to avoid a number of aquatic plants, including the Eurasian watermilfoil (Myriophyllum spicatum), giant reed (Arundo donax), hydrilla (Hydrilla verticillata) and water hyacinth (Eichhornia crassipes).

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