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I've heard that I should be piling dirt onto my potato plants as they grow so that I end up with little mounds.

My potato plants have started to poke through the surface. Should I totally cover them? By how much?

What is the purpose of this, anyway?

bstpierre
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lukecyca
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5 Answers5

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The whole point of 'earthing up' potatoes is to promote as much growth of potatoes along the stem while also protecting the potatoes from being exposed to light. If the growing potatoes are exposed to sunlight, they will produce the toxin solanine and become inedible. You know that spuds have been exposed to light because they also turn green due to the production of chlorophyll.

I start earthing up my potatoes when the leafy bits are just under 12 inches tall, making sure I leave some of the leaves exposed to the sun so they can carry on photosynthesizing - so not completely covered. I then do it once again a week or two later (depending on how fast they're growing) essentially until I run out of soil. The potato mounds in my garden are about a foot high or so.

Another way to ensure your young potatoes aren't exposed to light is to use black plastic to cover the soil, although this method requires you actively water your plants as the rain can't get through. A benefit of using plastic is that you have to do very little digging to get to your potatoes. This year I used a combination of earthing up and putting a thin layer of newspaper and grass clippings over the soil. We'll see how that goes...

Shanna
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Growing potatoes in mounds is a great way to grow them because it saves you from having to dig into the soil to pull up your potatoes.

Potatoes never grow any lower than where you planted your original seed potato, but you can grow them as high as the growing season will allow.

There are methods for growing potatoes up columns of tires which you might want to investigate.

Someone else will have to answer definitively how high to mound them, you should be able to cover most of the plant without hurting it.

bstpierre
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Peter Turner
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    ok, I'm going to have to look up the tire thing; it appeals to my inner redneck.. – Chance Jun 10 '11 at 13:34
  • http://www.bing.com/images/search?q=potatoes+tire pretty much tells the story. We do this and it's simple and straightforward. – Kate Gregory Jan 17 '12 at 19:45
  • agreed on the timing for burying them, BUT, don't use tires. would you eat off a tire? seriously toxic stuff. tires are great for non-edible plants, but please don't use them for food. –  May 04 '12 at 15:46
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    Tires are fine - ignore the "would you eat tires?" logic.. I would not eat dirt or cow poop either, but I *do* grow my veggies in both –  May 07 '12 at 12:43
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    Another minus for tires: you waste a lot of soil in the air part of the tire. Tires are free -- that's about the *only* plus I see. You can easily make shallow boxes that stack on top of each other to fill the role of tires, with less wasted soil and no chance of toxic residue. – Jan Steinman Jun 18 '12 at 18:21
  • I would also not eat dirt or cow manure, but I would eat the potatoes that are grown in it; the difference is that you can wash off any surface dirt, but many chemicals are actually taken up into the plant through the roots (and, by extension, through the actual tubers themselves). For example, it is actually important to test your soil for lead if you are near a source of lead-based paint. Lead stays in the soil for a long time, and while it does not reach the stems, leaves, flowers, etc., it IS stored in the actual potatoes (and carrots, and roots of many other vegetables). No, there is not –  May 13 '13 at 17:23
  • If you think it is ok to eat potatoes grown in a tire, you probably have no problem using loads of pesticides and herbicides in your garden - and don't even know what GMO means? The toxins in the tires will leach into the soil, and then the plants you plan to eat. What you put into your mouth is either medicine or poison. Think about it. –  Jul 20 '14 at 22:12
  • There haven't been sufficient studies on the absorption of tire-specific chemicals by potatoes—to my knowledge—to know whether or not it's a problem. Many plants do remove benzene from the air, however (burned tires do give off benzene, and other chemicals, I've read; I'm not sure what chemicals non-burned tires leach, nor if benzene stays in the plant afterward). If someone wants to risk it given the public lack of knowledge on the subject, that doesn't mean they'll *definitely* suffer (AFAIK, no one knows if it's safe, for sure). Sources may help here. – Brōtsyorfuzthrāx Dec 29 '17 at 03:05
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What I do is I take an old garbage can, and I put a layer of soil at the bottom and open a bag of taters and put them in a circle. Each time I see some leaves I put more straw on top until I can't see any more leaves. I water daily. I do this until the straw/leaves reach the top of the garbage can. I did this for the past two years and have had no issues. I'm curious if this is a preferred method? FYI I call this my "tater pit".

Zach Smith
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If it is early in the year and there is a chance of frost, you would cover them as soon as they poke through.

Another good time to cover with dirt is when you can see the potatoes poking through, this promotes more potato growth, but also prevents sunburn on the new potatoes forming.

Annie
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Most people plant their potatoes 1-3 times the potato diameter deep and "earth" or "hill" them as they poke through till the flowers come. This year I had a few left over and planted them in 3's in a 24" conainer. I covered them with 4" soil and as they poke through I'll add soil to the rim which will give me 12" soil over the seed. I am watered regularly and let's see if the yield is any better or worse.

robertfauchon
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