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I am under the impression that people grow potatoes in bags, containers, stacked up tires and so on because they get higher potato yields this way. The way I've heard it explained is that you plant the seed potatoes on the bottom and wait for the plant to grow. Keep adding soil every few weeks until you reach the edge of the container. Supposedly the roots will keep growing upward as well, and the whole container will be filled with potatoes.

I tried growing this way this year, and all my potatoes plants initially grew like crazy. I added soil as the plants grew, and eventually, I reached the edge of the container. The plants grew a bit more but mostly stopped adding new growth. Fast forward and my plants are starting to die back, so I harvest potatoes. To my surprise, all the potatoes were in one layer in the bottom of the container where I started the seed potatoes.

Reflecting back it seems pointless for the potato to put all that energy into growing a long stem and tons of leaves if I am just going to cover them with soil. The container did make it easier to harvest, but I did not have potatoes growing upwards in the soil as I expected. Is this an unusual result? Why bother growing in containers at all? Does anyone have any evidence that potatoes will grow all the way to the surface of the container?

  • Was there any drainage? What kind of soil and fertilizer did you use? – Shule Jul 27 '17 at 3:07
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    I used Miracle-Gro Raised Bed Soil, added compost and coffee grounds twice, once at planting and about a month later. Lots of drainage holes in the bottom of the container. – 1800-94-Jenny Jul 27 '17 at 3:12
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    I've tried many potato growing methods also, and I've also only had potatoes grow from the initial crown, not along the stem. My highest yields are from when I put 2 inches of compost on top of tilled soil, the lay the seed potatoes on top, and cover with chopped fall leaves. When the potatoes come through a bit, I add the leaves deeply, like 6-8 inches. No watering, no weeding, and no digging (all the potatoes develop between the compost and leaves, and are very big) – J. Musser Jul 27 '17 at 10:47
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    Potatoes only grow upwards in the sense that they grow on and may end up higher than the mother potato. Potato towers are a myth. – user10810 Jul 29 '17 at 9:40
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People use tyres, potato bags, containers etc instead of mounded earth on the ground because they're lazy (or have bad soil) and don't want to dig up the spuds at the end.

The big mistake I think is that they wait too long to heap soil on the growing stem in time. Once the stem reaches more than about 5 cm above the surrounding soil it can't switch back to producing stolons which grow the spuds.

Also, with bags, tyres etc, they get too hot and too dry. Once the soil temperature reaches 25 deg C a signal is sent to stop growing the spuds. And if they're too dry the potatoes are too small.

Potato bags also lack enough soil for the roots to get enough nutrition so you really have to grow in soil all the way down.

One way that may work is to use potato towers which are stacked boxes of wood that sit on soil. You add more boxes as you add more soil and make sure that you keep the growing shoot under 5 cm all the time. The boxes have holes in them so that any stolons that grow out of them can turn into stems that contribute to photosynthesis.

I have a thought, as yet untested, is that you can use these wooden towers but put the seed potatoes at the bottom, and fill right to the top right away. There should be enough energy for the potato to rise up through 2 feet of soil which ensures that the stems produce stolons without the risk that they become stems only. I'm going to try that next season.

25 kg of potatoes from 4 seeds in a tower

  • This is exactly the science based answer I was looking for. You’re explanation of the stems losing the ability to produce stolons explains why I’ve heard of potatoes sometimes growing higher up the stem in new soil but why it isn’t super common. I’d be very interested in hearing what happens with your potato tower experiment this summer. – 1800-94-Jenny Feb 6 '18 at 14:26

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