growing potatoes organically: when and how to plant, hill and harvest

hilled potato plants in raised bedA FRIEND I BUY seed potatoes with and I were scratching our heads as we filled out the order form, blanking on the line where it said “preferred ship date.” How early do we want them to arrive, we asked ourselves as we do every year. Time for a review of that and other questions about when and how to plant, hill and harvest potatoes. (That’s a row in my raised beds here, seen in late spring one recent year.)

Many companies ship extra-early, based on rough frost-date estimates for each area that may not be exactly what’s going on at your place, but is that really when I want the starts to arrive? I asked for advice from Alley Swiss of Filaree Garlic Farm, a longtime certified-organic farmer in Okanogun, Washington, whose main crops—garlic, shallots and potatoes—are favorites in my garden, too.

(Disclosure: I’m proud to have Filaree as a seasonal advertiser from time to time. You might recall the popular garlic-growing Q&A we did together last year; I’ve learned a lot from our ongoing conversations–including that it’s OK to wait a little while for the seed potatoes to arrive.)

potatoes dug from the garden

how to grow potatoes, with alley swiss

Q. When is the right time to plant—is there a cue in nature to remind us, or a soil temperature or calendar date we’re looking for?

A. At the earliest, I recommend planting two to three weeks before your average last frost date. Seed potatoes can rot if planted too early in cold water-logged soil.  If your potatoes do get a heavy frost after they emerge, they will put up new shoots, but every time they die back they will produce a smaller and later harvest.

I like to wait for the soil to warm up a little at which point they emerge quickly and grow steadily without stress.  Late March to early May is a good time to plant potatoes in the northern states.  In the warmer areas of the South they can be planted in late fall or early winter.

Where I farm the local point of reference is to plant your potatoes when the snow is almost melted off the mountain.  Whether it’s the first dandelions blooming or a particular bug emerging; if you talk to gardeners where you live they will probably have a local reference, too.

Q. Sometimes when seed potatoes arrive, some are nearly a tennis ball and some are mere eggs.  Should I cut the larger ones up, and do I have to let them callus before planting if so?

A. Many people choose to cut their larger sized-seed potatoes into pieces.  The advantage of doing this is your seed will go further and likely produce a higher overall yield.

If you do choose to cut your larger potatoes, make sure and leave at least two “eyes” for every piece. Use a clean, sharp knife to cut the potato into several large pieces shortly before planting.

Leaving the cut pieces in a cool and humid space overnight will give them enough time to callus before planting.  The callus will help prevent infection from soil contact.

We plant our seed potatoes whole to minimize worm damage.  If you have problems with wireworms, maggots or other pests, planting whole potatoes may be a good idea. Pests are attracted to the juicy exposed flesh of a cut potato.

Q. I have read so many variations about soil prep for potatoes. Is there something they do want, and anything they don’t? (For instance, I’ve read to avoid using manures on the potato bed.)

A. The ideal soil for growing potatoes is a loose and deep loam that holds moisture and also drains well.  Luckily, for those without “ideal” soil, potatoes are hardy and adapt well too many difficult soil types.  Lots of organic matter is recommended for the best yields. It is best to incorporate organic matter or compost into the soil in the fall so the soil has time to balance the added nutrients.

Fresh manure can activate the pathogen “scab,” which makes for unsightly, yet still edible, potatoes.  For this reason I use only well-composted manure when preparing soil for potatoes.  If you do not have access to composted manure, a well-balanced fertilizer can be used (I use an organic 4-2-2).  Too much Nitrogen will delay root production and you may end up with huge plants with little potatoes.

Q. So I’m ready to plant, following your above prep guidance. Now what? Proper depth and spacing—and is it the same whether a big baker or a smallish fingerling?

A. Dig a shallow trench about 6-8 inches deep. This can be done with a rake in loose soil, but you may need a shovel or hoe in heavier soils.

Place cut potatoes 10-12 inches apart in the trench. If larger potatoes are planted whole they will produce larger plants and should be given a little extra room, 12-16 inches.

A spacing of 36 inches between rows in adequate but if you have the extra space, further spacing will make hilling easier.

Fingerling and other small potatoes can be planted closer, but no less than 8 inches between plants.  Cover the plants with about 3-4 inches of soil, leaving the trench partially filled.

Q. The hilling thing is probably the most confusing part (and the most work). When and how deep and often do I hill, and where is all that extra soil meant to come from? Can I use straw or composted leaf mold or some other “mulch”?

Potatoes hilled a second time, with straw
A. Hilling is the most crucial, tiring and fun part of growing potatoes.  When your potatoes reach about 8-10 inches high, bring soil up around the vines from both sides.  This can be done with a rake in loose soils. If your soil is hard, you may need to cultivate the soil before raking or use a hoe.

Make sure not to cultivate too closely to the young plants as to not disturb the new roots systems.  Hilling brings loose soil around the vines where the potatoes will form as well as deepening the roots into cooler soil.  With the first hilling, I like to cover the vines up so that only the top leaves are exposed.  This allows for a shallower second hilling done 2-3 weeks later with an additional 2-4 in of soil brought around the vines.

A mulch that is loose and allows the soil to breath can be applied after, or instead of, a second hilling.  I recommend straw [above photo, a second hilling of straw in Margaret’s garden] because it breathes well, but leaves can be used as long as they are not applied too thickly.

A good layer of mulch can help protect vines from potato beetles by creating a barrier as well as providing habitat for insects that eat the beetle’s larvae. The fun part of hilling is looking at your beautifully hilled rows when you are done!

Fresh-dug early red-skinned potatoesQ. What’s the above-ground signal for when it’s OK to harvest new potatoes? Do all varieties offer this possibility?

A. Potatoes begin to produce tubers after flowering.  Several weeks after flowering, dig into the loose soil at the sides of the vines and you shouldn’t have to dig deep to find thin-skinned new potatoes.  These can be pulled from the plant without harming the development of the still maturing potatoes.

The waxier-textured potatoes are best for immature use.  The variety ‘All Red’ makes for a colorful new potato with bright red skin and a pink streak through the flesh.  ‘Yukon Gold’ is another early maturing variety with great flavor.

Q. How do I know when the crop is done, and how long can I leave them safely in the ground after that?

A. Potatoes are ready to harvest when their vines die back and they lose most of their color.  This can occur with a frost or simply when they have reached full maturity.

I like to mow the vines a few weeks before harvest.  This helps toughen the skins for good storage.

Potatoes can be left in the ground for several frosts, but should be harvested before the danger of a heavy frost that could damage the spuds lying closest to the surface.

  1. Terry says:

    Having rocky soil, we plant our potatoes ‘above ground’ using a group of old tires. We plant the potatoes in the middle of the tire on the ground and gradually add soil to the inside of the tire. At the end of the season, we remove the tire and easily harvest the potatoes. Our garden is behind the barn where the unsightly old tires are not a visual problem. You can also use a ring of chicken wire, which would look a little better. We have good luck with this.
    What’s your opinion, Margaret?

  2. Diana Pappas says:

    Great potato advice here. I’ve never really understood the point of digging a trench vs. digging holes – seemed like more work for the same result – but maybe this year I’ll be a little less lazy. My English in-laws who grow great spuds every year suggested a handful of well-composted chicken manure, and that made a big difference for us last year. Will definitely be doing so again, plus incorporating the tips above. As a side note, I love Filaree Farm! I’ve been getting my seed garlic from them for the past couple of years and the amount of garlic varieties they have is staggering!

  3. Chris says:

    Thank you for the clear and complete info on growing potatoes. We know they take alot of space, but still grow some every year, usually Yukon Gold.

  4. Rodney says:

    Thanks for the information I am planting regular potatoes for the first time this year as I had not wanted to use my space on potatoes however am expanding this year and looking forward to a crop of potatoes in the fall. Did plant some sweet potatoes last summer for my wife and had great success surprised her with them and she loved them!
    PS. Thanks for the input about the URL /Website tips. I am still quite a newbie! :)

    1. margaret says:

      Hi, Rodney. Glad to see you! (And happy to help.) I love growing sweet potatoes too (did you know the foliage is edible, sort of spinach-y?) but the woodchucks LOVE them more, so I gave up for awhile. :)

  5. Sharon says:

    Have heard that potatoes vector a disease which affects tomatoes…is that true? What is it and can I still grow both?
    Enjoyed your talk yesterday but could have listened twice as long!

    1. margaret says:

      Hi, Sharon. Because they are “cousins” botanically, yes, they do share some diseases. Potatoes left in the ground (accidentally) can be a vector for late blight the next year, for instance, even in the North. More on that. A Cornell article on the topic.

      Glad you enjoyed the talk. What a good group!

  6. Historically the potato was the food product of the poor especially in Ireland before the great famine in the 1800’s. Now it is a great healthy and low cost food even if you have some money hidden in your garden..

    Thanks for the tips…

  7. Debra says:

    We have tried growing potatoes the traditional way, in straw, in a barrel, you name it. Key word here is “tried.” But we have had LOTS of luck with sweet potatoes (like Rodney) which reminds me I need to go find some slips!

  8. loveliveandgarden.com says:

    Your veggies always look so beautiful! Thanks for the info! We are not really potato eaters around here but I was toying with the idea of planting them just for the heck of it. It is always fun to do something for the first time.

    1. margaret says:

      Thanks, LoveLive. They are fun to grow — and the first time you go to “pick” them and root around gently int he soil — it’s like a treasure hunt! Wonderful.

  9. Gisela says:

    Any tips on how to grow sweet potatoes in raised beds? Did not have good harvest last year. Any advise would be appreciated

  10. Becky says:

    Potatoes are one of those tricky crops for me to grow here in Florida. I rarely can find seed potatoes at the time that is most suitable to start them, so I’m left to pick them up at Aldi of all places in mid March. i don’t get a really big crop before it gets too hot for the potatoes, but I do get enough. But if you have a source for seed potatoes at a time better suited to the backward Florida growing calendar, I’d be so grateful for the info!

  11. Peg says:

    Hi Margaret. I have grown potatoes for years and always plant them on Mother’s Day or about a week or ten days before last frost date (for me). I let them come up a few inches, then hill them up to nearly cover them. I let them come up again and hill them once again. Then I mulch with as much straw as I can afford. When harvesting comes I can usually just scoop them up from the loose soil and the nearly composted stray. Yum! Can’t wait!

    1. margaret says:

      Hi, Peg. I never remembered to say to the seed-potato places to wait, and they’d send them in April here — sometimes early April. Too cold! They always survived, but I prefer to do them later, which I am now.

  12. Alicia says:

    Thanks so much! I just planted taters today and thought I was way late, but really Im about on time, woohoo! I think I planted them a little too close together, woops, but am happy to learn what to do once they start coming up. Thanks for the well timed information and details.

  13. Jane says:

    Ok, Becky from Florida says “before it is too hot for the potatoes”. Too hot for the plants? Will I have fried potatoes? Will potatoes not grow here in the Mojave Desert? Is it too late to start them? I was planning on growing them in a stacking set of boxes.
    :( Thanks for any advic you can give. And love the green pictures you post…..

    1. margaret says:

      Hi, Jane. In warmer climates, some crops are planted in fall (or even winter) to avoid the baking heat of midsummer. (So, for instance, one AZ cooperative extension document says plant from January to April depending on the area of the desert — high, low, etc.). I think the best place to start is your county cooperative extension website since I don’t know your precise location and when your frost-free times are and so on.

  14. Lillian Osborne says:

    What an informative post! Thank you.

    We are having some problems with scab in the potato plantings, and I have been giving thought to growing potatoes in wire cages or cedar boxes this season. Do you have anything as helpful on this growing method somewhere in your archives?

  15. Karyn says:

    I’m so glad to read this! I got a little bit of a late start on my garden this year and thought I wasn’t going to be able to plant potatoes because of it. Our last frost date doesn’t come for another couple of weeks, so I think I will go ahead and give them a try…Thanks for your post!

  16. Cynthia says:

    Hi Margaret,
    Your site is so helpful! This is my first year trying a small veggie garden; I followed your garlic planting instructions last fall and am thrilled to see little scapes popping up through the straw I placed over my raised bed. I’m also in zone 5b. Is it time to remove the straw yet?

  17. Thanks for the excellent article on growing potatoes! You’ve answered questions I didn’t even know I had. I’m also enjoying your great photography and slideshow on the right column. Can’t get enough garden photography this time of year, when I’m itching to see green and all we can see outside are the spring snowstorms.
    I’m signing up for your newsletter – thanks for the great content!

    1. margaret says:

      Glad to help, Lorraine. Yes, itching for the season to really unfold here, too. I expect peepers to start tonight or tomorrow…have been impatiently waiting!

  18. Allan says:

    To save some work growing potatoes, here is a tip. No trench is needed. Potatoes grow in hills on top of the ground. Plant the potatoes in rows, cover with two or three inches of soil. As the plants grow, hoe up more soil up to the leaves. I am able to to this about three times before the plants get to big to cultivate. Then mulch is great to keep the weeds out.

  19. Tim says:

    I’ve got a lot of field acreage and wonder where to find information/guidance on tractor planting, maintenance and harvest. Maybe I’ll ask Cornell Cooperative here in NY. A book would be great.

  20. Sheila says:

    Hi! Tanks for the great article!
    You seem to be a bit of an expert, so I hope you don’t mind my asking a question…I planted potatoes in a sack on my balcony last year, and they grew into healthy looking plants BUT I kind of forgot about them so I thought I’d killed them when the folliage disappeared. Then, this year they sprang back into life! I have loads of good looking foliage and have been watering them and topping them up as I should but my question is this: is there any reason they wouldn’t be good to eat? Does leaving them to fester in a bag of soil for a year do any damage?
    I hope you can help! Thanks in advance :-)

    1. margaret says:

      Hi, Sheila. Even here, in cold New York State a few hours north of NYC, the tubers will overwinter if I forget to dig them, or simply miss a few when I do harvest the rest. No worry as to safety I don’t think at all — but it will be interesting to see what kind of harvest you get.

  21. donna says:

    I planted my first potatoes this year and the plants look so beautiful every time I turn around they shoot up..can’t wait especially cause I went a bit wild and planted some blue ones

  22. Thanks for another great article, Margaret. I learned a lot, despite having grown potatoes for years. Love the Q & A format. I, too, tend to plant my potatoes later than most people here in my part of Missouri. This year I planted two raised beds a few weeks apart; the earlier one was hit by frost AND potato beetles, yet (knock on wood) so far not a single beetle on the second bed.

    I poached a few early Yukon Golds the other day from the first planting and they were fantastic. I was never a potato person growing up, but homegrown potatoes have so much flavor – just like everything else in the garden. We usually just boil them and toss with lots of organic butter and salt – then fry up the leftovers in a cast iron skillet. YUM. Thanks again.

  23. Nancy says:

    I am growing fingerling potatoes and mounded the soil two times, as recommended by most growers. My potato plants are getting very large and leggy and falling over, should I prune them or just let them lay on the ground? I can’t stake them for fear of damaging the potatoes, any advice welcome!

    1. margaret says:

      Here, too, Nancy — we have had a lot of rain so they are even more unruly than normal. : ) Do not prune! You can use straw or rotted leaves to mulch them more if you like, or just leave them be.

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