The short answer to that question is only if your fish will let you! Large koi may demolish or eat your plants but adding plant life to your pond is beneficial for Koi. The plants will also lift the look of your pond and transform it into a more beautiful feature of your garden.
But you need to choose the right plants and place them correctly so that they are not quickly consumed by the fish.
The benefits of aquatic plants in a koi pond
Aquatic plants are considered to be good additions to any koi pond. They help to increase oxygen production in the water and they keep the water cooler in hotter temperatures whilst creating shade for the fish. In spring, submerged vegetation provides a surface on which female koi can attach their fertilised eggs.
Plants also prevent the spread of algae as the shade they provide limits photosynthesis. Plants create a natural filtration system which restricts the formation of blanket weeds.
How to introduce your plants
The best way to introduce plants into your pond is to build a plant shelf. This can be constructed
along the edge of the pond. You should weigh down the plants with large rocks or stones as this will form a barrier between the plants and the fish and so restrict the number which are eaten! Do be aware that the plant shelf might make it easier for predators to feed on the fish and so preventative measures may be required to protect your stock
Floating plants, shallow-water marsh plants and submerged plants can also be placed directly into the pond.
Floating plants feature vegetation which sits on the surface while the roots hang down in the water. With some species, the roots may attach to the bottom of the pond. These plants provide shade for the fish and are generally easy to care for. Consider featuring water hyacinth, water lettuce, water lilies or lotus. Keep an eye on the growth of these species as they can get a little out of control.
Shallow Water Marsh Plant
These aquatic plants are typically planted on the edge of your pond in the shallow water. Consider water iris and horsetail for your pond. Umbrella is also an option but will not survive a harsh winter.
These species are grown in pots and then placed at the bottom of the pond. They are great oxygenators and remove excess nutrients from the pond environment but may be uprooted and eaten by the fish. Fanwort, American waterweed and water Purslane are good choices.
You might have to experiment to see what really works in your pond. With a little planning, you should be able to plant your pond so as to improve the water quality for the fish while also creating a more attractive look. You never know, you could discover a passion for gardening as well as for koi!