Worm Bed Potato Gardens – Update

Vermicomposting Potato Box
The potato plants are thriving in this vermicomposting bed

One month ago I wrote about some experimental grow boxes I had set up to see how well potatoes and bush beans would thrive in an active worm composting system (see ‘Worm Bed Potato Gardens‘). I was initially a little pessimistic about my chances of success, since unlike the vermicomposting trenches – which are essentially separated from the actual main plant growth zone – the potatoes would actually be growing right in the composting mass. My worry was that the volume of material in the bin would not only continue to decrease, but would also be unstable in general – due to all the activity of the worms down below.

In all honesty, the bush beans have not really thrived at all. My suspicion is that this has something to with the fact that, as legumes, these plants rely on a symbiotic relationship with Rhyzobium sp – the specialized group of bacteria that help them fix nitrogen. Given the fact that there is no soil in these boxes, and that it is a microbially-competitive environment (likely favoring those species adapted for life in a compost heap), it’s not really all that much of a surprise. Interestingly enough, aside from showing fairly poor growth, the bean plants have been quite yellow in color – often an indication that a plant is deficient in nitrogen. I did attempt to inoculate the plants with some soil (and plants) from patch of Black Medic (Medicago lupulina) – another legume – growing in my lawn, and it actually seemed to work (it worked very well in some other bean grow boxes I will write about in another post). I think it was simply a matter of being too little too late however.

As for the potatoes…

One look at the picture above should tell you just how well they are doing! I am starting to think this method may actually be a REALLY great way to grow potatoes! Of course, the real test will be to see how the potatoes look once it is harvesting time, but I’m certainly feeling optimistic! One or two people mentioned (in comments after the last potato post) the fact that it actually helps to continue mounding up material around the stem of the potato plant as it is growing, since this can lead to the formation of more tubers. As such, all the sinking and layering of materials taking place in these boxes may actually be exactly what these plants need to produce more spuds.

Essentially, what I’ve been doing is adding aged horse manure then covering it with straw. Once the level sinks noticeably, I add more manure (on top of the straw), along with a new layer of straw over top.

Aside from seeing how the potatoes would grow, I also obviously wanted to see how well the system would function as a worm bin. Initially, I was a little worried that the worm habitat would overheat by sitting out in the sun all day long. I’m sure our relatively cool summer has helped, but in all honesty I think my fears were unfounded. The worms seem to be doing extremely well, especially now that they have a nice canopy of foliage to shade the bin.

All in all, I am super excited about the results of this experiment since it has far exceeded my expectations…so far!
Stay tuned. More updates on the way (I will write more about my other vermi-gardens as well)

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    • Kim from Milwaukee
    • July 31, 2009

    Wow, what a beautiful potato crop! I’m gonna try putting my worms in my potato tower next year as well. That’s a great idea , Bentley.

    • Bentley
    • July 31, 2009

    Well – we’ll see how beautiful the ‘crop’ is once it comes time to harvest, but I am optimistic!
    Forgive my ignorance, but what exactly is a “potato tower”?

    • Eve
    • August 1, 2009

    Potato towers are a great way to grow potatoes. Adding one to the garden can add several square feet of growing space in one small spot.
    One of the best parts is the ease of harvesting, Just take the tower apart and the potatoes and compost fall out.

    The towers can be made of just about anything, boards to old tires. You can buy them too but home made ones seem to be more versatile.

    The potato towers don’t seem to do to well if there is only soil in the tower. It works best if you add layers of well processed compost, aged steer manure and straw. So you have all the correct ingredients going. All you need to do is go up.

    My tower is just 2×6 board walls that i add as the potatoes get about 6″ above the ground. Then i add more compost and straw as the plant gets taller. The growing season is short here, so the best i can get is 2 feet high. But in parts or the world where there is a continuous growing season potatoes can be harvested year round. The towers can get 4-5 feet high. They harvest by jacking up the tower the levering the bottom section out from under the stack. Then the emptied section is returned to the top of the stack for refilling. Just like using stacking worm bins. With a lot of back breaking work.

    Google potato tower and you will get a whole range different ideas on how to build one.

    • Bentley
    • August 1, 2009

    That is SO cool! Thanks for such a great explanation, Eve! More an more I realize just how much of a newbie I am with this gardening stuff.
    I’ve heard of using tires to grow potatoes, but that’s about it.
    Perhaps I should be creating some wooden additions for my boxes!

    • Red Worm Farmer
    • August 4, 2009

    Yes, Potato towers are great. I usde a 55 gallon drum cut in half to estblish mine.

  1. Bentley- how are you finding the moisture content of your potato worm bins? I put some worms in all my potato bins/ sacks/ towers but I have been disapponted with the number of worms in the mix when I harvest the potatoes. I wonder is it because worms like it wetter than the compost in the containers, and don’t breed as fast.

    • Bentley
    • August 5, 2009

    It’s funny you should mention that Catherine – i was just thinking today how a set up like this could potentially be a viable money maker in terms of potatoes, worms, and maybe even compost (since a fair amount of raw materials being added then converted into good stuff). I’m amazed by the density of worms in my boxes, and yeah it IS quite moist in there. Not sure if this will negatively impact the potato growth. I guess we shall see!

    What sort of ‘compost’ is in your systems? Mine was basically set up like a worm bed. I transferred a bunch of material containing lots of worms from another composter, and then simply added aged horse manure and straw on top in alternating layers.

  2. My compost is mainly home made garden compost, some worm compost (with cocoons), some bagged (bought) organic compost and a small amount of shop bought (rotted) horse manure. (I won’t be buying that again – there were alot of stones in it. But I don’t have ready access to horses). I also added some pelleted chicken manure for nitrogen. Maybe I needed to add some unrotted stuff like grass in my layers to keep the worms interested. But I think my main problem was lack of moisture. I don’t think potatos like it too wet- and it would only attract slugs anyway- but once there’s a good crown of leaves, it’s actually very hard to keep up with the amount of water given off.

    • Jennifer
    • June 29, 2020

    How did the potatoes turn out?

    • Bentley
    • July 8, 2020

    Hi Jennifer – this was quite a few years ago now. Think I did a final wrap up post, but the bottom-line is that the box system didn’t work very well. Would have likely worked much better had I just been layering in some sort of growing medium rather than try to keep an active vermicomposting system.

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