Lily pads, a generic name for water lilies (Nymphaea spp.) float on the surface of a pond. They produce attractive white or yellow flowers throughout the growing season. Lily pads can add aesthetic value to your pond or lake and also provide a haven for many fish and aquatic animals.
Despite their beauty, lily pads can take over a body of water very quickly, making it difficult to navigate boats or utilize for swimming areas. They reproduce through rhizomes in the pond bed and can take over the pond if not contained in underwater pots.
Fragrant water lily (Nymphaea odorata) is a particularly troublesome lily pad species with the ability for a single rhizome to form a 15-foot circle in just five years. Eradication is challenging but can be accomplished using several control methods depending on the volume of vegetation.
Standing in the pond – Manually grasp the lily pad stems as far below water as possible and pull the plants out of the ground, pulling up as much of the rhizomes as possible. I suggest wearing hip waders for this option.
Bow rake option – Drag a bow rake across the bottom of the pond to grab and pull up remaining rhizomes.You must dig in heavily to avoid scratching up surface of bottom and spreading rhizomes.
Weed circle claw option – Step on and turn a twisting weed grabber tool in the soil in the bottom of the pond. This specialized tool features claws arranged in a circle that loosen the rhizomes as you twist and pull them up as you lift it out of the soil. This is a difficult option and should only be used when the Lily Pads re-establish. Gather any lily parts from the top of the pond, using your hands if you are inside the pond, or by dragging the surface with a broom rake or net. The rhizomes should float to the pond surface, but it doesn’t hurt to rake the soil at the bottom of the pond to gather all the rhizomes. Discard the plant parts in a green materials waste bin or in your compost pile.
Sub-surface weed-guard barrier option – Cover the soil in the bottom of the pond with a benthic barrier fabric, a type of weed barrier that blocks sunlight and prevents rhizome sprouts from growing. This type of barrier only works after you’ve successfully removed the lily pad vegetation after killing the plants. Apply the barrier immediately after removing the vegetation or in early spring before any remaining dormant rhizomes awaken and produce new lily shoots.
Mix a glyphosate herbicide product labeled for aquatic use with a non-ionic surfactant and water in a garden sprayer or spray bottle, achieving a final dilution of 2 to 3 percent glyphosate. Exact mixing instructions vary with different products, depending on the percentage of glyphosate in a concentrated product. Aquatic glyphosate herbicide concentrated at 54 percent, for example, should be mixed at a rate of approximately 2 2/3 ounces per 1 gallon of water. Another 2 to 3 ounces of non-ionic surfactant helps the herbicide to coat the lily pads instead of rinsing away in the water. If you wish, add 1 ounce of a spray marking dye so you can keep track of which lily pads you have sprayed. AquaVet & Pond2O are national and regional brands that we recommend for high concentration and safety.
- Spray the top of each lily pad with the glyphosate herbicide solution until thoroughly coated. Follow all safety instruction on label ie. Wear protective goggles, long sleeves and long pants when applying the herbicide and keep children and pets out of the area while you’re working with the weedkiller. Allow approximately 10 days for the herbicide to transpire through the leaves and down to the rhizomes, killing the lily pads. The lily pads will first turn light green, then yellow and brown as they die.
- Drag the dead lily plants out of the pond with a bow rake or garden rake. Discard the plants in a compost pile or green materials waste bin.
- Spray a second round of the glyphosate solution to treat any remaining lily pads or any new plants that sprouted after the first application. Wait another 10 days or until the plants die, then remove the dead water lilies.