Worms and Potatoes

When I pulled back the worm bedding, this is what I found.

Two winters ago, J & I made a foray into vermiculture. We keep the worm bin in the basement, where we alternate layers of shredded newspaper with food waste. The worms plunder their way through this bin, leaving behind one of the richest manures on earth.

Throughout the winter, whenever I notice that something I’m storing in the basement has gone bad, I chuck it in the bin. (I store turnips, cabbages, squash, onions, potatoes, and other items in the basement over the winter.) In late winter this year, all the potatoes sprouted like crazy. Many of them were small and not worth saving, so into the worm bin they went.

Harvesting worm castings is a tedious job. The method is to make a bunch of little piles in the bright sunlight. The worms bury deep into the piles to avoid the light. You take the castings from the top and sides, then wait for them to bury still deeper and again scrape around the edges. But truthfully, you never avoid getting a bunch of the worms along with the castings—at least I don’t.  I tend to put the task off, but today I figured I better take advantage of the unseasonably warm weather to get the job done.  When I dumped the box onto a tarp, I found the most amazing thing.

The potatoes I had tossed in months earlier, had thrived in the worm bin. With no leaves for photosynthesis, these potatoes had somehow multiplied like crazy. The worms didn’t seem to be eating them at all, but they did seem to eat all around them. Many of these potatoes came out of the bin shiny and clean (though not the ones in the photo here), except that they were covered in worms that were not eating them. None of the potatoes had gotten very big—most were smaller than my pinky, but some of them grew in sizable clusters.

How did the potatoes grow without photosynthesis? None of the potatoes still had the sprouts that had caused me to pitch them in the first place; they were not even trying to get to sunlight or set roots. And why did the worms leave them alone? Was the potato growth simply able to outpace the pace of the worms, or did the worms avoid eating them for a reason? And why didn’t these potatoes begin to decompose anyway, even without the worms? They were in a moist, sometimes wet, place for more than six months, I’ve seen potatoes rot under much better conditions, even in the ground.  I have to wonder if there is some sort of symbiotic relationship going on. If anyone has any knowledge about this, I would love to know more!


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5 Responses to “Worms and Potatoes”

  1. Thomas Fortune Work Centre Gardening Group Says:

    Fascinating. I look forward to reading about any updates.

  2. Martha Gruelle Says:

    I did some digging on this–in our compost! Found a similar tater & tater tot. Don’t know dry weight of potato when it went into the compost, but I’m pretty sure the current tater + tot would be no more! What I noticed with the sample in hand was that the tater tot had grown off a shoot (not directly off the parent potato). It looked like the eye produced a shoot that found no sunlight and produced a tuber.

    So what are the primary decomposers for potatoes, and why aren’t they more common in garden soil and worm bins? Dunno.

    Btw, I use a more passive (easier) method to harvest worm castings: shove the old medium, worms, castings, etc to one side of the bin. Add fresh medium and food scraps to the other side. Wait a few weeks, and you can dig out the castings with most of the worms having moved to the fresh-food side.

    • erstwhile luddite Says:

      Thanks! Mine too had often grown off shoots, though some also grew right off a parent spud. I’m going to take another look in my worm bin in another and see if there are any new developments. And thanks for the tip on training the worms to separate themselves!

  3. Dolores Francis Says:

    This often happens with stored potatoes even if they are not in castings. (Unless, of course, you have children to go down to the dank, dark basement and pull the sprouts off.) A friend of mine actually plants potatoes in compost and says she grows a great crop.

  4. Chris Oinonen Ehren Says:

    This sounds like a great way to get your starter potatoes for the next year, if you could manage to control it.

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