Actually, from 2 sources. First, feeder roots do migrate down into the soil, but the tuber production takes place on top of the soil. Second, as the hay or straw breaks down over the growing season, it also provides nutrients. I have grown potatoes this way sucessfully for many years. Just be careful to keep the nitrogen low so you don't have long healthy vines, and poor tuber set.

Ron
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sophia: I recommend you use lots of straw. I have grown potaoes under straw, but too many of the tubers became exposed to light and turned green and inedible. I went back to growing in soil and hilling, but I do use a heavy straw mulch once they are hilled. This seems to delay the onset of Colorado beetle infestation. To disuade the Colorado beetles, by the way, you need a soil with all the right minerals in balanced quantities, so - importantly -make sure you have sufficient calcium and phosphorus. Also I add a pinch of vitamin C as I plant each potato, which seems to help. Regards, Peter.

Peter,
The rule of thumb is to pile on 18" of loose hay or straw when you surface plant. It mats down to 10-12", and when it does, I like to add a bit more. If you use the right amount of mulch, you don't have any problems with the green taters!
You are correct about the Colorado Beetles not liking the hay. They hate the stuff, and you never have a beetle problem using hay for mulch. It works every time!

Ron
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Thanks for your help. I have bales of straw, very loose and not broken down, and I have my own mulch of very fine straw, broken down over the winter on that field (which I raked up before burning). So now: I should dig a trench of some sort, so there will be some loose soil under the straw, right? Should I use both loose and already broken down straw directly on top of the potatoes? I had read that, later, you can mulch up to 3 or 4 feet, to avoid the problem of green potatoes....but I just did not understand how they could get nutrients from just straw. I am also using Garden's Alive Root fertilizer, I presume it is organic.
sophia

If you were going to plant about 3 seed potato portions with two eyes each in shredded leaves in a white 5-gallon bucket with big holes in the bottom, would it work?? Does it have to be in the full sun? Should it have some compost or container soil (6 inches?) in the bottom and you just keep adding shredded leaves when the sprouts show a little bit?
Thank you -
Sunny

Sophia,
I have grown potatoes right on top of sod, without touching the soil, and gotten great results. The only thing I use is a little bonemeal which just sprinkle right on top of the hay. It migrates through when it rains.
Potatoes produce better quality tubers and shorter top growth on fair to poor quality soil. I wouldn't even bother to touch the soil at all. I suggest using the loose straw until the vines poke through, and then you can gradually add the fine stuff as the continue to grow. As long as you have vine coming through the mulch, you can't use too much.
I also grew potatoes on the same bed for many years, using the previous years hay, and adding more as needed. Many say this is a no-no, but I just got better results with each succeeding year. Just never use lime or wood ashes, because the raised pH will cause scab. Good luck!

Ron
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Hey Sunny,
I would suggest putting a few inches of good compost or rich soil in the bottom, laying the seed potato pieces on the surface and covering with several inches of those shredded leaves you have. As the vines start growing, keep adding more shredded leaved until the bucket is full.
Be real careful about over watering. They won't need much watering with all that mulch, and too much will kill the plants or rot the tubers. I have seen this work well but on a larger scale - with a 30 gal. plastic garbage can. And yes, they do best in full sun.

Ron
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Hi folks, I have another question on this topic if I may.

I found some advice online to put a tomato cage with 18" of hay above my seed potatoes. I did, and they sprouted and just shot out the bottom of the cage (just like I thought they would do...)

Any suggestions on what I should do now? I have 9 hay filled tomato cages in a square about 1 ft. apart. I guess I could just get more hay and cover everything. Would it be a good idea to remove most of the hay from the tomato cage, move the sprouts to the center of the cage, and pile more hay on top? If so, how much?

Thanks,

Tym