Aquatic Weed Contol

John Madsen
March 2022

In many ways, aquatic weeds are similar to terrestrial or land weeds. There are annuals and perennials. Many flower and produce seed, others propagate only asexually. Some produce tubers or winter buds, some are more shade tolerant than others, and nearly all respond to fertilization. Therefore, the management and control of these pests is similar in many respects to that of land weeds.

Usually, aquatic weeds are separated into four broad categories: emergent, submersed, floating, and algae. Emergent plants (sometimes called bank or marginal plants) are those rooted or anchored in the substratum with most of the leafstem tissue above the water surface. They do not rise and fall with the water level. Examples are: cattail (Typha spp.), Bulrush (Schoenoplectus spp.), and horsetails (Equisetum spp.). Submersed plants are adapted to grow with all or most of their vegetative tissue below the water surface. Examples of submersed plants include pondweeds (Potamogeton spp.), coontail (Ceratophyllum demersum), and Brazilian elodea (Egeria densa). Floating plants are those that are either free-floating or anchored to the substratum. They produce most of their leafstem tissue, or thalli, at or above the water surface. Leaves or thalli of floating plants rise and fall with the water level. Examples of floating plants include the duckweeds (Lemna spp.), azolla (Azolla spp.), and fragrant waterlilies (Nymphaea odorata). Most algae are also submersed and free-floating. However, some may be anchored by holdfasts to the substratum, rocks, old stumps, and other objects. Algae do not have true roots, stems, or leaves and are frequently called “pond scum” or slime.