Common Floating Weeds: Types and Solutions

     Continuing our focus on common nuisance algae and aquatic plants, today's article discusses Duckweed, Watermeal, and Mosquito fern, featuring a video and slides from resident algae and nuisance plant expert West Bishop.

Duckweed (Lemna minor)

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Duckweed is a very small floating plant. It has shoe-sole shaped leaves with a small hair-like root hanging on its underside. It resembles a four-leaf clover and is approximately the size of a pencil eraser. It is frequently misidentified as algae. Once established, it can cover the entire water surface and resemble a golf course green. It can cut off sunlight to submersed plants and cut off oxygen to fish and other wildlife.

Watermeal (Wolfia spp.)

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Watermeal is often recognized as the most difficult aquatic plant to control. It is the smallest of flowering plants and can be dark to light green in color. It resembles tiny grains of sand or cornmeal, and often looks like very small dots covering the pond. Reproduction occurs by splitting, so complete coverage of a pond’s surface is rapid.

Mosquito fern (Azolla)

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While typically small in form, Azolla plants are capable of doubling their mass in as little as 3-10 days and can form large mats on the water surface if left unchecked. The plant's numerous, closely-overlapping, and water-repellant leaves aid in floating, and most often appear brown, green or red. Its quick growth is due in part to its symbiotic relationship with a type of cyanobacteria, which supply the plant with nitrogen by fixing it from the atmosphere.

Duckweed, Watermeal, Mosquito Fern & Their Solutions

 by West Bishop (video)

This short spot from West Bishop (in a presentation with GCI) discusses what to look for with duckweed, watermeal and mosquito fern, and offers advice on chemical control options for irrigation and non-irrigation water bodies.