Whether you like them or not, lily pads have an undeniable charm, especially when they flourish in the middle of a pond filled with colorful fish. On the other hand, although they are attractive aquatic plants, they can quickly invade your beautiful ponds to the point where you do not know how to control their population. And if more than half of the surface of a body of water is covered with lily pads, this can cause certain problems.
There are two main methods to get rid of them: chemical and mechanical.
However, be aware that any chemical method carries risks for your fish and the ecosystem of your pond. Use this method sparingly, and only if you have exhausted all mechanical solutions beforehand.
In addition, it is strongly discouraged to eliminate all the lily pads floating on the waterbody, as they provide the oxygen essential to fish populations and create shade areas favorable to many aquatic species.
Table of contents
Before You Start: What You Need to Know
Lily pads (Nymphaeaceae) are essential plants of a pond. From spring, usually in May, the flower buds emerge one after another from the water. These “floating islands” serve as a refuge for many small animals.
The lily pads are also the primary source of color in the pond. Many water lily flowers exude a delicious scent; flowering lasts all summer and continues until fall. On the third or fourth day after hatching, the flower remains closed, sinks very slowly, and will never open again.
Lily pads are part of your pond ecosystem
These graceful aquatic plants are not just decorative elements. They also contribute to the biological balance of your pond. Indeed, the floating leaves protect the water from the sun’s rays and thus prevent the proliferation of algae. In addition, water lilies absorb nutrients typically used by algae, limiting their proliferation. As a result, the water, free from too many algae, remains clean and clear.
These plants also provide shelter for fish in times of danger. The leaves provide shade, preventing the water from heating up too quickly on hot summer days. In addition, water lilies produce oxygen released into the atmosphere.
To maintain a good biological balance, part of the water must remain covered with floating plants. The smaller the pond, the more plant cover should be. For a pond of 20 by 50 feet, 50% of the water surface should be covered with floating (leafy) plants. For a smaller pool of 10 by 10 feet, 60% coverage is ideal. So, be careful not to remove too many lily pads from your pond; otherwise, the delicate balance of the aquatic environment will be weakened.
Method 1: Remove the Lily Pads Mechanically
Step 1: Rake Them
If the lily pads invasion is still small and their roots are not too tangled, it is possible to rake them by hand. Use a classic garden rake. However, depending on the variety, the roots may be more resistant, and you may not be able to pull them out. So, this is a good short-term solution, but the lily pads may grow back again.
Step 2: Introduce Herbivorous Fish in Your Pond
Putting lily pad-eating fish in your ponds is a good biological solution. However, be aware that some species may not be native and can become invasive. One herbivorous fish is usually sufficient for a small pond. In addition, fish eat more when they are juveniles.
What Fish Eat Lily Pads?
Koi carp and goldfish are greedy creatures that love to nibble on water lilies. Grass carps are also fish that will enjoy devouring these aquatic plants.
Step 3: Uproot the Lily Pads with a Shovel
If your pond is shallow, go straight in. Push the shovel under the root of the lily pad and lift it. Pick up the plant with its root. However, this solution can be time-consuming and difficult if you have a large water area and you are alone. However, it has proven to be effective as a long-term solution.
Step 4: Try the Aquatic Mower
As the name suggests, this is the equivalent of a land mower designed to prune plants that grow on the surface of a body of water. The aquatic mower is typically used for algae control, but you can also use it to trim lily pads.
Method 2: Remove the Lily Pads with Chemicals
For chemical treatment, however, it is best to wait until the end of the first flowering. Indeed, this treatment is more effective and less harmful if you wait until the first flowering is over.
Step 1: Determine Which Areas to Treat
In general, you should treat from the pond’s center to the periphery, working area by area. If you spray an entire pond at once, you risk causing a large amount of organic matter to decompose and therefore dangerously lower the oxygen level in the water. To prevent this from happening, start with the most affected areas and wait a few weeks before treating the other sections.
Step 2: Apply an Agricultural Surfactant
You can apply the herbicide directly to the leaves, but usually, a surfactant is needed to dissolve the protective wax coating on the leaves. Generously spray the surfactant on the surface of a lily pad.
Step 3: Choose the Right Herbicide
Herbicides containing glyphosate are commonly used to control lily pads. You may already be familiar with this herbicide, as it is often sold under the brand name Roundup.
Another proven product is Imazapyr. These herbicides are broad-spectrum, which means they are not selective and kill all plants on the water surface. And if you’re worried about their toxicity to your fish, here’s what the National Pesticide Information Center (NPIC) and the Wisconsin Department of Natural Resources are saying about them:
- Imazapyr is practically non-toxic (the EPA’s lowest toxicity category) to fish, invertebrates, birds, and mammals.
- Pure glyphosate is low in toxicity to fish and wildlife, but some products containing glyphosate may be toxic because of the other ingredients in them. Glyphosate may affect fish and wildlife indirectly because killing the plants alters the animals’ habitat.
Step 4: Apply Herbicide to the Lily Pads’ Leaves
Follow the directions on the package for the correct dosage. Usually, herbicides are sprayed onto leaf surfaces until completely covered.
Step 5: Remove the Dead Lily Pads
Once the plants are dead, they will continue to float on the surface of the water; so, you will have to pick them up one by one. If possible, also collect the roots. These are probably dead too, but it’s best not to let them decompose in the pond.
Step 6: Repeat the Treatment for Several Weeks
Wait two or three weeks between each application and treat a small area at a time to avoid unbalancing the medium. Then, when you have treated the entire surface, treat the first area again if many lily pads have survived the first treatment.
A Few More Tips
- Wear protective clothing, such as boots and a raincoat, when removing the lily pads from your pond. If you are applying chemicals, wear protective gloves and goggles.
- Learn about the regulations. Some areas are protected due to the exceptional flora and fauna they shelter. You risk being fined if you tear off lily pads when it is prohibited. Even if the pond is on your property, you may be subject to special regulations if you are in a protected area.
Despite the beauty and usefulness of water lilies in a pond, you may need to reduce their population. Mechanical methods, although time-consuming, have the advantage of being virtually harmless to the flora and fauna that inhabit your ponds. However, you may need to repeat this method frequently, as if you were mowing the lawn. Chemical methods are riskier for your fish, but they are generally more effective. If you opt for the latter, be sure to read the product label, wear protective gloves, and do not hesitate to call a professional if in doubt.
Featured Image Credit: NT Franklin, Pixabay