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.For more information on tips for post winter koi pond usage.
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.
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.
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.
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.
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.
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.
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.
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.
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 and requires a good deal of light. These plants can grow up to an inch per day and can be propagated using cuttings.
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.
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.