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Overwintering Duckweed

September 20, 2013
Turions and mother fronds of Spirodela polyrrhiza  Photograph courtesy of Prof. Cheryl C. Smart

Turions and mother fronds of Spirodela polyrrhiza from “The Charms of Duckweed” by Dr. John Cross Photograph courtesy of Prof. Cheryl C. Smart

Do you hate to see your duckweed freeze and die every late fall?  If you are like me, you’ll be glad to know that while the bulk of it WILL die as your ponds freeze over, some of your duckweed has gone into hibernation mode and will return in the spring. Here is how:

Duckweed forms specialized small fronds called turions in the autumn. These turions are composed of starch to roughly 70% of its body weight instead of the normal 15-40%.  Starch is heavier than water so this allows the turions to sink. Depending on the species, some only sink a few inches below the water surface while others sink down into the mud where they wait patiently for spring. Then they begin photosynthesis and form little air pockets which makes them boyant. They rise back up to the water surface and begin growing out normal daughter fronds.

You might assume like I did that the formation of turions was temperature-related. Actually, it has to do with the amount of phosphate in the water column. Dr. Klaus Appenroth of Jena, Germany has been studying turion formation for over a decade and discovered this in his research.

So what does that mean for our in-ground duckweed ponds and above ground kiddie pools?  If you are in the frigid north, ensure you have a deep enough ponds that will allow mud to remain unfrozen during the winter. Kiddie pools may not be deep enough. You can always bring in a container of duckweed water and put it in a cool southern window. Or you can let Nature take its course. If your kiddie pools of duckweed totally freeze, source a new batch in the spring from nearby wild ponds.

A little batch of duckweed in a glass bowl on your windowsill looks amazing against the backdrop of a January snow fall.

3 Comments leave one →
  1. September 30, 2013 4:57 pm

    Hi Sue, Less phosphate induces turion formation.

    Like

  2. Susan Munroe permalink
    September 29, 2013 1:06 pm

    Re: the phosphate… does that mean more or less phosphate/phosphorus? Should I add some chicken poop to the containers to add more, or hold off?

    Like

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