Yellow water lilies are perennial plants that arise on flexible stalks from rhizomes and large fleshy roots that can resemble bananas. Leaves are oval heart-shape, 3 to 6 inches in diameter, shiny dark green on top and reddish-purple underneath Leaves float on the surface and are seldom emergent. Flowers are large (2 1/2 to 4 inches) bright yellow and usually stand above the water on separate stalks. Yellow water lilies can reproduce from seeds or by spreading of the rhizomes.
Submerged portions of all aquatic plants provide habitats for many micro and macro invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.) After aquatic plants die, their decomposition by bacteria and fungi provides food (called “detritus”) for many aquatic invertebrates. Deer occasionally consume the leaves of yellow water lilies, while ducks consume the seeds and roots as do muskrats, nutria, and other rodents.
Mechanical/Physical Control Options
Yellow water lily can be cut and the rhizomes can be dug up but physical control is difficult because it can reestablish from seeds or remaining rhizomes.
Biological Control Options
There is no known biological control for yellow water lily.
Chemical Control Options
The active ingredients that have been successful in treating yellow water lily include 2,4-D (E), fluridone (G), glyphosate (G), and imazamox (G). E = excellent, G = good
Navigate and Weedar 64 are 2,4-D compounds that have been effective on yellow water lily. 2,4-D compounds are systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides.
Rodeo, Aquamaster, Eraser AQ, Touchdown Pro, and AquaNeat are liquid glyphosate formulations and have been effective on yellow water lily. These are broad spectrum, systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides. An aquatically registered surfactant (see the label) will have to be added to the Rodeo solution for good results.
Sonar and Avast are fluridone compounds, come in both liquid and granular formulations, and have been effective on yellow water lily. These are broad spectrum, systemic herbicides. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides.
Clearcast is a liquid imazamox formulation. It is a broad spectrum, systemic herbicide. Systemic herbicides are absorbed and move within the plant to the site of action. Systemic herbicides tend to act more slowly than contact herbicides. An aquatically registered surfactant (see the label) is needed for application.
Habitat contains the active ingredient, imazapyr, which inhibits the plant enzyme AHAS (acetohydroxyaced synthase). Habitat is a systemic herbicide that is effective on post-emergent floating and emergent aquatic vegetation. Imazapyr is effective at low-volume rates and does not contain heavy metals, organochlorides or phosphates, making it safe to humans and livestock. Habitat requires the use of a spray adjuvant when applying on post-emergent vegetation.
One danger with any chemical control method is the chance of an oxygen depletion after the treatment caused by the decomposition of the dead plant material. Oxygen depletions can kill fish in the pond. If the pond is heavily infested with weeds it may be possible (depending on the herbicide chosen) to treat the pond in sections and let each section decompose for about two weeks before treating another section. Aeration, particularly at night, for several days after treatment may help control the oxygen depletion.
One common problem in using aquatic herbicides is determining area and/or volume of the pond or area to be treated. To assist you with these determinations see SRAC #103 Calculating Area and Volume of Ponds and Tanks.
Many aquatically registered herbicides have water use restrictions (See General Water Use Restrictions).
To see the labels for these products click on the name. Always read and follow all label directions. Check label for specific water use restrictions.
Yellow water lily can be propagated by transplanting rhizomes into shallow, clear water during the winter.