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What is all that Green Stuff on Glade Run Lake?

Updated: Feb 4

Written by Dave Fowler, Board Member with the Glade Run Lake Conservancy

Many visitors to Glade Run Lake often comment on the unsightly green "scum" they see on the water's surface, asking what can be done to get rid of it. To some, it may come as a surprise to know that all that green material is actually a combination of different plants (depending on where in the lake you're looking), and may not be as bad as you think, nor will it last into the wintertime.

Dave Fowler, blog author, paddles on Glade Run Lake in October 2021. The green "scum" visible on the lake is actually a combination of two plants; duck weed and water meal. The plants seen to the right of Dave's boat are Eurasian water-milfoil, an aquatic invasive species.

The green "scum" on the surface on Glade Run Lake is not primarily algae and not really scummy if you touch it. It is comprised of two plant species, water meal (Wolffia sp.) and duckweed (Lemna sp.), both of which are among the smallest flowering plants in the world.

Water meal can be identified by its texture; it feels like corn meal if you get it on your fingers. It's also very small; about the size of a poppy seed, and has no roots. Duckweed is larger than water meal, much softer, and has roots. It is, however, also a very tiny plant - smaller than a pencil eraser.