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Overwintering Duckweed Indoors

October 31, 2012

Every fall, I survey my assorted outdoor pots of tree seedlings, tropicals, and herbs to see which gets brought into the house and thus saved a certain death from ice and snow. In years past, I’d end up with literally a  jungle in my sunroom, complete with banana trees, figs, taro, and lots of giant fern specimens. Now, I’ve got a home with limited southern exposure, so it’s extra sad to have to pick who lives and who dies.

The winners this year are my  frost-sensitive Haas avocado seedlings that are 3 ft tall with beautifully shaped leaves, as well as a pomegranate bush that is spectacular. Also this year, I’ve decided to overwinter a nice batch of duckweed under a simple flourescent light fixture above a desk in my office. When January rolls around, that bright green duckweed is going to be a cheerful counterpoint to ice and snow outside.

I’ve divided the duckweed and replant half in a larger container already. I use a weak solution of 20-20-20 once a week as a fertilizer. It’s mostly Lemna minor but little dots of Wolffia are beginning to grow larger every day. The duckweed came from a wooden half barrel of water lilies. It was hunkering down for a winter hibernation, so this change in temps and light intensity has been an adjustment for it.  I use Pyrex glass baking pans but also a stainless steel restaurant sized lasagna pan that isn’t pretty but holds a lot of duckweed. I leave the lights on for roughly twelve hours a day and position them about four inches above the plants.

Usually around mid-January, my green thumb starts itching and I long for the scent and color of green plants. Sprouting wheat berries for wheat juice helps, but usually I need a fix of walking slowly through a greenhouse, breathing deeply of freshly released oxygen and enjoying thousands of plants in the winter sunlight. Maybe the duckweed will be enough to keep me going until spring. Maybe I’ll still need to hunt up a florist’s greenhouse, or build a makeshift cold frame for lettuces. It’s probably a sign that I was meant to live in a more tropical climate but I try to bloom where I’m planted here in Kentucky. Already, I’m imagining the scent of freshly sprouted tomato seedlings! This is going to be a lonnngggg winter.

5 Comments leave one →
  1. Susan Munroe permalink
    November 10, 2012 4:18 pm

    I looked up both, and they don’t look like pollywogs (haven’t seen any of those for decades!). The mosquito larvae photos all looked older than what I’ve got, but that must be what they are. One would think two nights of 26F would take care of them.


    • November 11, 2012 7:43 pm

      Guess it’s a water temperature issue, rather than an air temp one.


  2. November 9, 2012 11:43 pm

    Could be mosquito larvae. Doesn’t sound like tadpoles. You might google images of mosquito larvae and see if they are the same. If the water is warm enough, you could probably get mosquito larvae all year long. A really thick stand of duckweed inhibits their growth usually. Just to be safe, I wouldn’t leave your water sample inside your house. If they ARE mosquitoes, once they emerge from their “tumbler” stage, you don’t want to have them buzzing around indoors.


  3. Susan Munroe permalink
    November 9, 2012 8:57 pm

    Hmmmm….. What are these?

    I scooped out the last of the Lemna by flashlight. In the kitchen, I saw these “things” wiggling around.

    I’m thinking they’re pollywogs or mosquito larvae. But it’s November — isn’t it far too late for both of those?

    They wiggle, then rest, then wiggle, etc. Brown. They have a couple of tiny antenna-looking things.

    Any thoughts?



  4. Susan Munroe permalink
    November 1, 2012 2:36 pm

    I was just looking at my duckweed (after the duck attack, which decimated it considerably), and wondering what to do.

    Your idea gave me an idea! I have one of those silly “garden tubs” that takes the contents of two hot-water tanks to fill. I use it for storage, and the cats use it as a place to park to watch the birds in the backyard.

    I could put some water in it, mix in a little duck poop, toss in the Lemna and give it a stir!

    GREAT idea!



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