Duckweed Removal

What you are dealing with

Duckweed is a free-floating plant, not one rooted to the bottom, so it drifts with the wind and piles up thick on the downwind bank. Each plant is only a few millimeters across, but there are millions of them, and under good conditions the population can double in a couple of days. What looks like a light green film on Monday can be a solid mat by the weekend.

That mat is a problem for the whole pond. It blocks sunlight from anything growing below it and it cuts off the surface where the water takes in oxygen. Under a heavy duckweed blanket the water can go low on oxygen and put stress on your fish. It also just looks like a putting green laid over your pond.

Why spraying does not fix duckweed

You can spray duckweed and kill a lot of it, but the dead plants sink and rot, and the same nutrient load that grew the first blanket is still in the pond to grow the next one. Duckweed multiplies so fast that any survivors or any new drift-in repopulate the surface quickly. So you spray, it clears for a bit, and it is back, with more dead matter on the bottom each time.

Because duckweed floats free and moves with the wind, a neighbor pond or a wet ditch upstream can reseed yours after a spray. Killing it in place does not deal with the load of nutrients that makes your pond a good home for it.

How duckweed removal actually works

We skim the mat off the surface with the rake, working the downwind banks where it piles thickest and pulling the floating blanket up onto the shore. Because it floats, it comes off in sheets. We make passes across the surface until the open water is back and the green carpet is on the bank drying out.

Taking the plant matter out of the pond takes its stored nutrients with it, so the pond is slower to blanket over again. On ponds that keep getting reseeded by wind or runoff we can talk about a maintenance visit, but there is no monthly contract and no standing charge. You call when it needs it.

What happens to what we pull out

Skimmed duckweed is light once it dries and makes good compost. Most owners leave it on-site to break down. We can also move it to a spot on the property or haul it off as a paid add-on. We go over the choice before we start.