Adding plant life to a koi pond helps improve pond life for koi, as well as adding beauty to the pond itself.
Koi owners need to make sure they select the right aquatic plants that will harmoniously co-exist with their koi. They also need to ensure that their plant placement is done properly as well as not planting vegetation that will just be eaten by the koi!
The benefits of including aquatic plants in a koi pond
Aquatic plants are considered an excellent addition to any koi pond. Aquatic plants, in fact, help increase oxygen production in the water, helping to keep the pond properly aerated for koi. Their presence also helps keep the water cool by providing shade to the koi. Additionally, around the spring breeding season submerged plants act as a critical surface onto which female koi attach their fertilized eggs.
The presence of plants also prevents the spread of algae from getting out of control. The shade plants provide reduces incoming light into the pond and therefore limits photosynthesis of algae. Their natural ‘filtration’ system prevents blanket weeds (string algae) from forming, mainly through absorbing harmful nitrates that lead to their formation in the first place.
Tips for introducing koi to plant life
The best way to introduce plants into a koi pond is building a plant shelf. This shelf can be built along the edge of the pond itself. It’s a container where water plants are suitable for planting. It’s a good idea to weigh down the plants with large rocks or stone to form a barrier between the base of the plants and koi, preventing the risk of the koi eating the plants. Pond owners should be aware that predators like raccoons may use the shelves as a tool for feeding on your koi. For more on how to prevent pond predation see this article.
A vegetative filter may be an alternative to introducing aquatic plants to your pond. In this system the plants are grown in a separate containment area that connects to the main pond. The plants here can serve as a natural filtration system as water from the main pond travels in and out of the contained area. This gives you all the filtration benefits of having aquatic plants without the risk of your pond plants being eaten or dislodged.
Of course, you can always place aquatic plants directly into the pond itself. There are several options to choose from when deciding on which aquatic plants to put in your pond. Pond plants can be divided into 3 main categories that are discussed below:
1) Floating plants
2) Shallow-water marsh plants
3) Submerged plants
1) Floating Plants
This type of pond plant can be truly free floating with its main vegetation on the surface while the roots hang down, unattached or there are types where the roots are attached to the muddy bottom. The benefits are that they are easy to care for, they provide plenty of shade for koi and they compete with algae for nutrients as well as blocking light that would have otherwise helped algae to grow, all of which greatly reduces algal growth. Additionally, they remove a lot of the existing nitrogen and phosphates in the water and thereby do a great job of filtering the water.
Some popular choices for floating plants are water hyacinth. This species is an annual in the colder regions of North America but a perennial in the warmer parts of the States. They bear purple or blue flowers and their roots form a compact “nest” beneath them. These plants do a great job of filtering the water of excess nutrients.
Pros: Grows and reproduces easily, good filtration of nutrients
Cons: Growth can get out of control so be sure it doesn’t find its way to public waterways. Natively free floating so more difficult to protect from nibbling koi.
Another free floating plant is water lettuce. This is more of a tropics/warm climate plant and forms compact leaf clusters on the surface with a compact root mass forming beneath the plant.
Pros: Forms dense top cover providing shade and hides fish from predators.
Cons: Can be invasive and out of control if let loose in public waterways.
When it comes to floating plants with attached roots water lilies are definitely the most popular choice amongst koi pond owners and may be the top choice of any of the aquatic plants. These plants will do well in just about any region of North America in any season and can be potted and placed at the bottom of the pond. On the surface, pond owners with water lilies will find a pleasant array of leafy covering and beautiful flowers that will nicely accent any pond.
Pros: Adds beauty to your pond, will assimilate excess nutrients.
Cons: Growth can be excessive, will need to be regularly maintained in smaller ponds.
Looking similar to water lilies the lotus is one of the oldest cultivated aquatic plants and make a great addition to any koi pond. Their leaves are typically very large, as much as 18 inches across which is great for providing shade to your koi in the summer. Often confused with water lilies the lotus flower is very beautiful and also fragrant. A word of caution should be noted here as these plants have a substantial growth rate and are best planted in larger koi ponds.
Pros: Looks great in your pond.
Cons: Requires lots of sun and low humidity.
Water poppies produce small oval leaves and yellow flowers and are a great choice for koi ponds. They grow fairly quickly in summer and add a nice touch of yellow to your pond while filtering the water.
Pros: Good looking plant for margins (edges) of ponds.
Cons: Susceptible to frosts.
2) Shallow Water Marsh Plants
These type of aquatic plants are typically planted on the edge of your koi pond in the shallows. They are usually very lush and do best in only several inches of water.
These tropical region aquatic plants do well in shallow water and for those living in colder climates they need to be brought in during winter. Umbrella plants, as the name suggests, have umbrella-shaped leaves at the end of long stalks.
Pros: Very nice addition to pond margins
Cons: Depth limitation of 6 inches or less.
A favorite amongst koi pond owners the water iris comes in several different species. They have long, sharp leaves and depending on the species may produce flowers in colors ranging from blue, white or yellow. These plants are typically planted in pots that are then submerged. Most iris will do great both in full sun or partial shade which is nice for those with a lot of tree cover nearby.
Pros: Aesthetically pleasing, forms good cover for fish. Remove toxins well.
Cons: Susceptible to pests.
These pond plant references have served me well over the years. You can learn more about them below.
This plant produces a slender green stem and is fast growing. It is best placed on the peripheral parts of your pond and will do great in partial shade.
Pros: Great water filtration.
Cons: Can get out of control if not maintained.
3) Submerged Plants
Suberged plants are usually grown in pots then placed at the bottom of a koi pond. Referred to as oxygenating plants this class of aquatic plants do a great job of removing excess nutrients from the water such as nitrites as well as CO2 and add oxygen to the water. One word of caution though, these plants are often uprooted and eaten by grazing koi so care must be taken to protect them.
This submerged plant is a fast growing oxygenator (much like the similar Hornwort) and requires a good deal of light. These plants can grow up to an inch per day and can be propagated using cuttings.
Pros: Good attachment plant for koi eggs during breeding, good oxygenator.
Cons: Won’t do well in shade, needs plenty of sun.
American Waterweed (Elodea)
These plants do well with pond substrates that are silty. They are completely submerged with the exception of small white flowers that bloom at the surface. It is great at utilizing the dissolved CO2 in the water and providing cover for fish, especially small koi. Sometimes the leafy stalks will break off and float away to take root in another part of the pond. They do very well in milder climates.
Pros: Good place for koi eggs to attach, will stay green year round (through winter), will assimilate excess nutrients.
Cons: Can get really out of control and should not be allowed in public waterways.
Water Purslane (Ludwigia)
There are many species in the Ludwigia family but Red Ludwigia is a good choice for your pond as this plant grows fast and is a great oxygenator. It can be planted as a submerged addition to your pond or you can let it float. They produce small flowers and their leaves are a reddish or purple color. They typically do well in a lot of direct light.
Pros: Many species exist so there will be one for your region. Generally hardy.
Cons: Edge planted forms will produce fine seeds that can blow onto and germinate in wet lawns. Submerged forms need plenty of light for ideal growth.