Lotus Is it Friend or Foe?
During spring and summer, many people become concerned about plants growing in their ponds. This concern may or may not be justified, because aquatic plants are desirable for many pond management goals. Lotus (Nelumbo lutea) is a conspicuous emergent aquatic plant that frequently grows in local ponds. Lotus has several other common names such as yoncopin, water chinquapin, yellow nelumbo, pond nut, rattle nut and duck acorn. Lotus has large, round, entire leaves that float on the water or perch above the water. A lotus leaf does not have a slit unless it is torn. The flower is large and pale yellow. The stalk bearing large seeds bends over in the fall, and the large holes in its flat surface cause it to resemble a shower head. It typically grows in water 1 to 6 feet deep and seldom persists long in water deeper than 7 feet.
Lotus somewhat resembles water lily and cow lily (also called spatterdock), and many people mistakenly refer to all three of these plants as water lily. But, lotus and cow lily are not water lily. Lotus is in the family Nelumbonaceae, while water lily and cow lily are in the family Nymphaeaceae. Leaves of both water lily and cow lily have a deep slit, notch or sinus. Water lily leaves usually float or sometimes slightly elevate above the water, while cow lily leaves float or stand above the water like lotus. Depending upon species, native water lily flowers can be white, blue, lavender, rosy or yellow (there are additional colors in cultivars). Cow lily flowers are yellow, but much smaller than lotus or water lily, and cow lily flowers do not open up to show the inside portions of the petals. Water lily and cow lily have round fruit that mature underwater and are much smaller than the conical lotus fruit that usually mature above water. Water lily and cow lily are less common than lotus in most portions of south-central Oklahoma and north-central Texas.
Whether a pond manager should be concerned about lotus in a pond depends upon lotus abundance and a manager's goals for a pond. Lotus is a pretty plant that adds to landscape beautification. The seed heads are frequently used in dried flower arrangements. Its seeds, tubers and young unrolled leaves are edible for humans. The seeds are eaten by mallard and wood duck, the roots are eaten by beaver and muskrat, and the stems and leaves provide shade and habitat for fish, young waterfowl and marsh birds. Shade from its leaves can limit abundance of submersed aquatic plants. However, lotus can be aggressive and dominate most portions of a pond shallower than 7 feet, making boating, fishing, seining and swimming difficult. Abundant stands of lotus can limit more preferred duck food plants such as pondweeds, smartweeds and naiads.
When control is appropriate, lotus can be reduced with biological, mechanical or chemical means. Grass carp of adequate size at an appropriate stocking rate can reduce lotus. Information about stocking grass carp is addressed in a June 1997 NF Ag News and Views article that is accessible on the Noble Research Institute's Web site at www.noble.org. Considering lotus depth limitations, a pond can be designed or deepened to minimize the area where lotus can grow. Lotus is susceptible to 2,4-D, glyphosate and triclopyr herbicides. These herbicides allow a pond manager to sculpt a stand of lotus and manage where lotus grows and where it does not. When using 2,4-D in fishponds, use amine formulations rather than ester formulations, because 2,4-D esters are toxic to fish. Additional information about chemical control of aquatic plants is addressed in a March 1998 NF Ag News and Views article that is also accessible on the Noble Research Institute's website. Always read an herbicide's label and use it accordingly.