The 15 Best Plants for Koi Ponds (With Photos!)
Plants are a great addition to koi ponds and even provide a wide range of benefits for the pond and the koi living inside them. But which are the best ones to grow? Choosing mediocre plants is easy but to keep your koi fish happy and your ponds healthy, here are some of the best plants you can grow in your koi ponds.
The 15 plants that are best for koi ponds are:
- Watercress
- Smartweed
- Dwarf papyrus
- Iris
- Water lotus
- Mosaic plant
- Sweet flag
- Hornwort
- Water soldier
- Taro
- Water poppies
- Fiber optic grass
- Duckweed
- Creeping jenny
- Eelgrass
With how many aquatic plants there are, it can be a bubbling source of anxiety trying to decide which ones to get. But don’t worry! To help save you the trouble, here are some of the best plants you can grow for your koi ponds, all in one place.
1. Watercress (Tropaeolum majus)
Watercress is a useful pond plant that requires little maintenance. Storebought watercress can be grown directly in ponds to combat single-cell algae and provide koi fish with extra sustenance. Growing watercress can lead to invasive growth, however, and is even banned in Illinois.
Plant Type: Floating
Light: Full sun to light shade
Consumed by Koi: Yes
Watercress is an easy growing plant that doesn’t require much maintenance. These plants are frequently used to help keep pond water clear by competing with the single-cell algae that makes ponds cloudy, for food.
To make things even better though, these plants are cheap and probably readily available to you! You can buy fresh watercress at your local supermarkets and simply place the strongest and freshest stems in the pond to let them grow.
The only con to this plant is that they’re pretty invasive. It’s even prohibited in Illinois.
Pond owners can have an extremely difficult time trying to remove them if left unchecked.
But you can prevent this from happening by regularly removing unwanted watercress from the roots and letting the koi munch on it as they please throughout the day.
2. Smartweed (Polygonum affine)
Smartweed is an emergent plant that is highly effective in clearing ponds by removing undesired contaminants. To shield smartweed from unwanted feeding, grow them in aquatic pots or keep them surrounded with rocks to block off koi fish.
Plant Type: Emergent
Light: Full sun
Consumed by Koi: Yes
Another great pond plant that can help filter out unwanted impurities lingering in the pond is smartweed.
Because they’re emergent, their roots grow underwater while they bloom above the surface. So you can enjoy their attractive flowers as the plant becomes older!
Koi are known to sometimes nibble on smartweed. As such, you can easily grow smartweed to act as another food source that’s high in nutrition.
But if you’d rather not have your koi eat them, you can grow them in underwater pots to help protect them from hungry fish.
3. Dwarf Papyrus (Cyperus alternifolius)
The dwarf papyrus can develop thick roots underwater that are frequently utilized in underwater filtration systems. However, these are often known to clog up pipes in ponds and must be handled carefully. Papyrus plants are rarely consumed by koi.
Plant Type: Emergent
Light: Full sun to partial shade
Consumed by Koi: No
This plant doesn’t seem to be eaten as much by koi, so you should be able to plant this leafy papyrus in your pond without any fear.
Papyrus can quickly shoot up in height in just a short amount of time, growing wide spirals at the tips to spread outwards. Another important thing to note is these plants look like green fireworks!
Established papyrus plants can produce thick roots to serve as an underwater filter.
These outstanding root systems can become an issue for some folks, though, by blocking and clogging up waterways. Keep them confined in aquatic plant pots to prevent this.
4. Iris (Iris hexagona)
Irises are commonly grown in ponds due to their ability to reduce excess nitrates and algae. However, this bulb plant is poisonous to ingest and may be a risk to koi fish. Therefore, irises are best grown further up streams away from areas with high fish activity.
Plant Type: Marginal
Light: Full to partial sun
Consumed by Koi: No
When it comes to some of the best pond plants, irises are a favorite of many pond owners for several reasons.
To start, while irises are bulb plants, they’re wonderful for bogs and ponds because of the fact they are marginal plants and can stand in up to 5 inches of water.
Moreover, irises produce vibrant blooms and are often planted to help absorb excess nitrates in the water.
However, irises are also known to poison both animals and humans when ingested, so it may be risky growing these in ponds with ever-hungry koi.
It’s highly recommended to keep koi fish safe by planting irises in a filtering stream leading to the pond while still keeping them away from koi fish.
5. Water Lotus (Nelumbo nucifera)
Water lotuses are commonly cultivated for their attractive blooms. Their wide and accompanying lily pads also offer pond waters and their occupants adequate shade. These plants are useful in reducing algae and are not palatable to koi.
Plant Type: Emergent
Light: Full to partial sun
Consumed by Koi: No
Ponds hardly seem right without at least a handful of water lotuses growing in them. Their colorful flowers are enchanting to look at and you’ll most likely find their abundant circular leaves quite helpful.
Water lotuses are technically emergent plants; you can find their thick roots growing deep underwater. But because water lotuses tend to grow a vast amount of floating leaves, they will provide the same benefits as floating plants.
Their wide, disc-shaped leaves live on water surfaces and will help prevent the sun from entering the water.
With less sunlight able to penetrate through ponds, algae is less likely to grow. So you can enjoy clearer waters and pretty blooms with little maintenance.
6. Mosaic Plant (Ludwigia sedoides)
Mosaic plants are highly sought after for their diamond-shaped foliage and are ideal for ponds that receive at least 12 hours of direct sunlight per day. Like other common floating plants, however, they are prone to koi consumption and must be grown away from active waters.
Plant Type: Floating
Light: Full sun
Consumed by Koi: Yes
Since mosaic plants require at least 12 hours of full sunlight daily, they’re great for ponds bathing under sun.
This tropical floating plant grows diamond-shaped rosettes that are sometimes tinted red. Established plants will grow an abundance of these leaves to adorn water surfaces.
Because all their leaves usually mesh together perfectly, they can look like dragon scales or mosaics and will make a lovely addition to water gardens.
Koi fish may choose to eat these plants though, so this plant is best for ponds with a low population of fish or best grown in separate areas.
7. Sweet Flag (Acorus calamus)
Sweet flags can be grown to encircle and conceal ponds with 12-inch grass-like growth. These plants can tolerate being grown in 2–3 inches of water to provide koi fish with shelter. Hence, it is ideal for ponds that are frequently attacked by unwanted animals, like herons.
Plant Type: Marginal
Light: Full sun to light shade
Consumed by Koi: No
Sweet flags have scented narrow leaves that make them similar to grass, so they can easily be used as a charming filler plant to surround ponds.
These plants are typically found in boggy wetlands and flourish when they’re planted in about 3 inches of standing water—making them a great choice for ponds.
Although they grow best with plenty of strong of sunlight, they’ll also do just fine growing in partial shade.
Not only do they serve as a pleasing textured filler plant, but sweet flags can also be grown in dense strips to surround ponds. Doing so will further add to its seclusion, preventing anything from intruding.
8. Hornwort (Ceratophyllum demersum)
Growing hornworts to filter out green koi ponds has been practiced for years. Hornworts are effective oxygenating plants that thrive at pool bottoms by consuming the water’s nutrients and competing with algae. Despite their lack of roots, hornworts are weedy and must be verified before planting.
Plant Type: Submerged
Light: Partial light
Consumed by Koi: Yes
Hornworts, also known as coon tails for their bushy appearance, can be quite soft and will probably be seen as very appealing snacks to koi fish.
Now, despite how inconspicuous these small stems may appear, they’re one of the most common plants I’ve been told to get for koi ponds.
Why, you ask?
Once hornworts are placed in green algae-filled ponds, they’ll help keep the water clear by feeding off the nutrients in the water and reducing any algae in the vicinity.
They’re also relatively hardy plants and can survive light frosts if they’re kept completely submerged. However, since this plant lacks roots, they can sometimes be seen floating up to the surface of ponds.
Coon tails are quick to grow back but are seen as invasive and have caused some problems in New Zealand by outcompeting their other native plants. So be sure to check whether or not you can grow this beforehand!
Hornworts are very low-maintenance plants frequently used in water gardens and aquariums, so it’s no surprise they’re ideal for koi ponds as well.
9. Water Soldier (Stratiotes aloides)
Water soldiers are frost-hardy and self-propagating plants that do not require much attention. Although they are buoyant aquatic plants, koi fish seldom attack them due to their rigid and serrated leaves.
Plant Type: Emergent
Light: Full sun to partial shade
Consumed by Koi: No
Building and maintaining koi ponds can be tiring so having easy-growing plants like water soldiers is excellent.
This leafy aquatic plant usually lives in ponds with about half of their growth below water. They require very little to no maintenance and can be left to float freely in your koi pond.
Additionally, water soldiers grow serrated leaves. This is probably why they aren’t disturbed by koi fish very often.
Water soldiers are self-propagating and sink to the bottom of ponds in the winter to protect themselves. So there’s no need to replace them seasonally. You can just leave them in your ponds! Talk about low-maintenance.
10. Taro (Colocasia esculenta)
Growing taro is an effective way to provide shade to strongly lit koi ponds. Mature taro plants can be 3-feet high and are purposefully grown at the edges of ponds to offer shade. However, taro plants are toxic when ingested and help deter unwanted animals from disturbing koi ponds.
Plant Type: Bog
Light: Full sun to partial shade
Consumed by Koi: Yes
Taro plants, or elephant ears, are vibrant tropical plants with huge heart-shaped leaves. They grow well by the wet edges of ponds. But I have also seen folks grow taro in containers and leave them in the water.
Because they can grow over 3 feet tall, you can position established taro plants on the outer rim of your ponds and use their great leaves to help provide some shade.
Another crucial thing to note is that taro plants contain toxic calcium oxalate crystals that can cause severe pain if they’re eaten raw. Some koi owners note that their fish don’t seem to be bothered by this and even frequently attack taro plants.
To be safe, though, I suggest keeping these plants outside of the pond where their toxicity can be used to repel unwanted animals like deer or raccoons.
Grow the black-leafed varieties to use as a stunning backdrop for more colorful pond plants.
11. Water Poppies (Hydrocleys nymphoides)
In general, water poppies thrive in waters of 70°F and are ideal aquatic plants for warm climate ponds. Wide leaves aid in halting algae development by preventing sunlight. However, water poppies are not hardy and will perish in frost.
Plant Type: Floating
Light: Full sun to partial shade
Consumed by Koi: Yes
Water poppies are vibrant aquatic plants that can be grown no matter what size pond you have. Similar to lotuses, their flat and green leaves can help block sunlight from entering the pond and encourage algae growth.
Yellow blooms can often be seen sprouting above the water, especially in the summer. But
there is one disadvantage to this plant.
Unfortunately, while water poppies look charming, they’re not at all frost-hardy. This means you’ll have to skim these plants out of the pond before winter to prevent them from rotting.
Take them out early on to ensure they do not leave any dead growth behind, or plant only a handful of water poppies to enjoy.
12. Fiber Optic Grass (Isolepis cernua)
Fiber optic grass is easy to cultivate. Utilize this grassy plant to add texture in between rocks in koi ponds or grow it in 2–3 inches of water to provide koi fish shelter from predators. Despite their misnomer, fiber optic grass is not grass and is rather a sedge that koi seldom eat.
Plant Type: Marginal
Light: Full sun to partial shade
Consumed by Koi: No
Although this plant is not grass like its name implies, fiber optic grass has the same, wiry texture to it that many pond owners enjoy.
Fiber optic plants are evergreen, so you can easily buy this at any time of the year! Its grass-like nature makes it a great supplemental plant for more dramatic statement pieces.
This sedge is not difficult to grow at all. I’ve worked with this plant before and can say their seeds grow quite readily and very quick to germinate. To make things easier, though, you can just propagate this plant vegetatively and plug them wherever you wish.
It is unusual for it to be eaten by koi fish, so you can use this evergreen all year around the edges of the pond or let their pots stand in up to 3 inches of water.
13. Duckweed (Lemna minor)
Duckweed produces floating layers of miniature leaves on water surfaces that can be used for both shade and cover. Similar to other floating plants like water poppies, this plant should only be grown in small quantities to avoid becoming invasive. Duckweed is easily consumed and even enjoyed by koi fish.
Plant Type: Floating
Light: Partial to little shade
Consumed by Koi: Yes
If you like the floating features of lily pads and water poppies but do not like their size, duckweed can be a great alternative!
Duckweed is one of the smallest aquatic plants available. Their blanket of tiny, flat leaves can serve as a great surface cover for koi as well as an extra source of food.
They’re high in nutritional value for koi but it’s extremely important to only grow this plant sparingly and as a special treat.
Like other floating plants, they can quickly become invasive and are not hardy to frost, which means you’ll have to keep an eye on them and pull them out during the winter.
14. Creeping Jenny (Lysimachia nummularia)
In koi ponds, creeping jennys can be grown and used in a variety of ways. These trailing plants thrive in damp areas and can be used to decorate neighboring stones and walls. If grown submerged 1–2 inches underwater, koi fish may hide beneath their foliage or consume them when hungry.
Plant Type: Bog
Light: Full sun to partial shade
Consumed by Koi: Yes
This versatile plant can be grown in a variety of different ways in the pond garden. I’ve seen creeping jennys, or moneyworts, be used in a variety of different ways.
Moneywort flourishes in moist environments. It produces round trailing leaves that you can use to decorate walls, rocks, and more.
You can grow them in containers and allow their foliage to cascade down streams and waterfalls or use it as a groundcover; the possibilities are endless!
Alternatively, this bog plant may also be submerged as food or shelter for smaller fish.
Creeping jenny plants may enjoy wet environments but they may rot if they’re left in extremely deep water for long periods, so just keep them in an inch or two of water.
15. Eelgrass (Vallisneria spiralis)
Eelgrass is a useful pond plant that is commonly cultivated for its ability to provide new oxygen in the water while simultaneously clearing it of nitrates. They are low-maintenance seagrass that koi often hide in.
Plant Type: Submerged
Light: Bright to medium indirect light
Consumed by Koi: No
Finally, eelgrass is one of the few essential pond plants that many water gardeners recommend to me for maintaining a healthy pond.
This wavy seagrass plays an important role in ponds by acting as an oxygenator and providing safe habitats for koi fish to find refuge in.
These underwater ribbons grow quickly and are known to consume much of the nitrates in the water, making it much easier to maintain crystal clear ponds.
Eelgrass still requires some sunlight to thrive on the bottom of your pond, however, so be sure not to cover the entirety of the surface with floating plants.
10 of the Worst Plants for Koi Ponds
The worst plants to grow for koi ponds are those containing highly toxic compounds, like cardiac glycosides, that may kill koi fish and those that are extremely aggressive in growth. These plants include:
- Aconitum (Monkshood): Highly toxic
- Buttercup (Ranuculus, Crowfoot): Highly toxic
- Cattail (Typha spp.): Highly invasive
- Foxglove (Digitalis Purpurea): Highly toxic
- Oleander (Nerium oleander): Highly toxic
- Philodendron (Philodendron): Highly toxic
- Pickerel Weed (Pontederia cordata): Highly invasive
- Rhododendron (Azalea): Highly toxic
- Water Hyacinth (Eichhornia crassipes): Highly toxic and invasive
- Water Lettuce (Pistia stratiotes): Highly invasive
When selecting new plants, those that are invasive in ponds and very toxic to koi fish really should not be considered. These may be perhaps the worst and most risky plants to grow that can harm not only koi but other animals, like cats.
Many pond owners have attempted to grow the aforementioned plants inside or near their koi ponds, only to experience their koi fish dying after eating the toxic plants. Others had to deal with weedy ponds when the plants grew out of control.
Of course, you can grow whatever plants fit your needs and water gardens. But because of how precious koi fish are, it is always recommended to only choose what is best for not just you, but your koi fish and your pond.
FAQs
Why should plants be used for koi ponds?
While koi ponds can be kept without the use of plants, it’s not often recommended. Plants can bring in their own unique complications to ponds but are extremely beneficial in a variety of different ways, such as keeping ponds clear and providing koi with extra food and shelter.
Where can I buy pond plants?
Pond plants encompass a wide range of aquatic and tropical plants and can easily be found in aquatic shops. Local plant nurseries can also be checked and consulted with. If pond plants are not available in one’s area, they can also be found online.
Summary of Best Plants for Koi Ponds
The best plants for koi ponds are those that grow easily in damp or wet areas and regularly help clean ponds by filtering out nitrates to reduce algae growth.
Some of these helpful plants for koi ponds include watercress, smartweed, dwarf papyrus, irises, water lotuses, mosaic plants, sweet flags, hornworts, water soldiers, taro plants, water poppies, fiber optic grass, duckweed, creeping jenny, and eelgrass.
Sources
- “Water Gardens ” by n/a in University of Florida
- “Sea Science: Eelgrass: Binge Eaters in the Estuary” by Pam Smith in University of North Carolina
