Want to Grow Sweet Potatoes? Now’s the time to start!


UPDATE:  March, 2017 I discovered an even better,  more reliable way to start slips for Sweet Potatoes.  The way I explain to do it in this blog post still works and it works well, but my second method makes the process more predictable and produces more robust slips (believe it or not how robust your slip is has no effect on the end sweet potato so don’t worry too much if you have sickly looking slips).

I’m having a LOT of trouble focusing on my posts these days. It happens.  As soon as there’s anything that can be grown, seeded, started, planted or propagated I can’t be trusted to do anything else.  I’ll pretend to do other things.  At this moment for example, I’m sitting at my desk pretending to write a post.  When in fact what I’m doing is stringing a few words together to form a bunch of sentences which is NOT to be confused with actual writing.  Don’t be alarmed if you thought what you were reading was writing. It’s a common mistake.

It’s pretend writing which isn’t real writing.  It’s fake.  It’s just the illusion of writing. Now that we’ve established that this post is  the trompe l’oeil of words we can move forward without you having any real expectations from this post or the “writing”.

I’m back.  I bet you didn’t even know I was gone.  Well I was, I got up and walked away from my computer just a few sentences into the post because I wanted to check to see if the sweet potatoes I’m propagating had started to sprout yet.  They haven’t.  I’ll check again in 5 minutes.

There are a few things I’ve started for the garden that are therefore constantly on my mind.  Onions, leeks, and sweet potato slips.  Onions and leeks have to be started stupid early and so do sweet potatoes. Which means I’m a bit of a fool starting around March. You’ve heard of baby brain I’m sure.  This here is worse.  This is horticulture head.

SO … I DRAGGED MYSELF AWAY from watching my sweet potatoes not grow to let you know


Sorry to be so loud about it but I wanted to make sure you got the point.  Want to grow sweet potat …

I’m back.  This time I actually left you for quite a while. Of course you have no way of knowing that, but in fact, I walked away from my computer for an hour and a half because it suddenly became of the utmost importance that I drive to the grocery store to procure more sweet potatoes for propagating.

I’ve written about growing Sweet Potatoes before but I’m going to break it down even more this time around with some more specific information that should help you be successful.  I grow Sweet Potatoes in Zone 6b by the way, this will be my fourth year doing it.  And you can do it too.

What you need:

Sweet Potatoes



WARM place (80F or warmer)

3 months!



  • Place sweet potatoes in a glass jar  of water (like a mason jar).  You want half of the sweet potato under water and the rest not. The part under water will grow roots and the part above water will grow sprouts (known as sweet potato slips).   If your sweet potato is too skinny you can use toothpicks to keep it from falling right down into the  jar of water.
  • Put the jar with the sweet potato somewhere WARM.  Over 80 degrees Fahrenheit is ideal. And the warmer the better.  I have a dining room cupboard that’s next to a heat vent. I know the cupboard always gets warm because of the vent so I put my sweet potatoes in there.  A check with a thermometer showed that cupboard is indeed 80 degrees inside.  At this point the sweet potato doesn’t need any light.  Just warmth.  Now just leave the sweet potato and wait.
  • It could take as long as a month or more for the potato to start growing “slips”.  Just keep checking them every few days to see if they’ve started to sprout.
  • They might grow roots before they grow slips so check for those too.
  • Once they sprout you can put them either under grow lights or in a warm, sunny window.  You still want the sweet potatoes to be in as warm a place as possible, but now you also need light for the sprouts to grow.
  • Once the sweet potato sprouts are 5″ or so long you can break them off of the potato and put them in a jar of water.  It won’t take long before your slips will grow their own roots in water.  Once they have a nice little group of roots you can plant them in soil.  However chances are by the time you’ve grown the slips and rooted them, it’ll be time to plant them in the garden.  Sweet potatoes take a long time to root and produce slips, but the warmer their conditions the quicker this process will go.
  • Sweet potatoes can’t be planted until the soil is VERY warm.  A good rule of thumb is to plant your sweet potatoes two weeks after you’ve planted your tomatoes.




This is a store bought sweet potato. Just a regular one, not organic.  The organic ones were only sold in bags for $8 for 4 and in past years they haven’t been any better than a regular sweet potato for producing slips. Which is contrary to everything I’ve been told on the Internet (which is that regular ones will have been sprayed with a sprouting inhibitor that prevents them from producing slips).  I get slips from store bought, home grown or organic.

Other than this year.  This year my sweet potatoes won’t grow because I forgot and left them in my mudroom when it was REALLY cold for a few nights.  That means they got below  (way below) 55 degrees fahrenheit.  Once they do that, the sweet potato is damaged and chances are it will never sprout for you.  I was counting on growing slips from the sweet potatoes I grew last year so I didn’t order any slips this year.  Which means I’d better hope these grocery store sweet potatoes are a) short season sweet potatoes because that’s what will grow here in Southern Ontario and b) ready to produce slips for me.

Some Sweet Potato Growing Tips

  • If you want to try growing sweet potato slips from grocery store sweet potatoes, check for cold damage on them.  Cold damage doesn’t show up until a few days after the sweet potato has been exposed to below 55 degree temperatures.  On the inside (which you can’t see) the sweet potato will have dark spots.  On the outside the sweet potato will have dark discoloured spots and lesions.
  • If you’re feeling extroverted you can seek out the produce manager and ask if he happens to come across any sweet potatoes that have sprouted to save them for you.
  • 2 weeks prior to planting your sweet potatoes, lay plastic on the soil.  It can be clear or black plastic.  Clear plastic sold in rolls for home vapour barriers is ideal. You can get it at any home improvement store. This plastic will increase the temperature of your soil by 10 – 15 degrees which the sweet potatoes will love.
  • When it’s time to plant your sweet potato slips, just cut a hole in the plastic about 4 or 5 inches across and plant the slip.  The cut out hole allows for water to get to the sweet potato roots so you’ll grow bigger potatoes.  If you also push the edges of the hole down, it will help direct any water right to the plant.
  • Sweet potatoes can be dug up just before the first frost, although they won’t grow much once the weather starts to get cooler.  If your soil temperature is consistently cooler than 60 degrees fahrenheit (18 celsius)  they won’t grow anymore and risk cold damage. Wanna know how to test your soil temperature?  Just stick a thermometer in it.



This potato has the start of chilling injury from being stored below 55 degrees fahrenheit. Notice how icky it looks. It’s still fine for eating just not for producing slips.





 This is a sweet potato that’s been stored at the proper temperature.

 This is what your sweet potatoes will look like once they start to form “slips”.


This was an organic sweet potato I sprouted a couple of years ago. It did no better than …


 … the regular sweet potato from the section of the grocery store where people with kids shop because for now they can’t afford to buy both diapers and organic produce.

Oh are you still here?  Sorry.  I was gone for a bit again.  I was laying out the new sweet potatoes I bought and making space for them in my dining room cupboard.  You might as well leave now. I have a feeling if I

Sorry.  You lost me there again.  For the love of all that is good in this world … just go.  No WAIT!

Tomorrow I announce my next live video course, SEED STARTING! sponsored by my favourite source for seeds, Cubit’s seeds.  It’ll be a quick and dirty (literally) one night class covering everything you need to know about starting seeds with live demonstrations. More on that tomorrow.

Kay, now you should probably go.

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  1. j says:

    I didn’t know you back when coop cam was started, is there any way for me with only my Mac – no smart phone, no tablet, just me and my Mac – to observe your chickens? Thanks for your help!

  2. Barbie says:

    Perhaps I will Try some sweet taters this year ….thanks fer yelllin at me to member to do it NOW!

  3. Merlin says:

    My parents grow sweet potatoes for their market garden business and my Mum has a few tricks up her sleeves.

    Mum has never had any luck starting her SP’s in water. What she does is sink a potato half into a box of potting soil, place that box on top of the heat mat, and water the heck out of it. She gets slips in about 2 weeks. You can buy heat mats at your local hardware store. They’re about 19.99$ for a small one.

    And whatever you do, do not use clear plastic. The weeds that grow under it are horrendous! Black plastic is available at a lot of Home Hardware’s in Canada or, you could use a black lumber tarp to trap the heat.

  4. Amber says:

    For all you Monarch butterfly lovers, this is also the time to start your milkweed seeds! 🙂
    Old milk jugs work well: punch some drainage holes in the bottom, cut through 3 sides half-way up, fill the bottom with soil, push in seeds, water well, and close the top down so you’ve got a mini greenhouse. You can use duct tape to keep it closed, and the lid off to keep it from being too wet. In a few weeks you’ll have lots of food for those baby caterpillars.

  5. natalie says:

    Yay, I love sweet potatoes! It’s one of the few veggies that 3 out of 4 people in my house agree on (the fourth pretty much only eats fruit). I’ve got 2 black thumbs but I’m going to try this anyway. How often should the water be changed? (Please don’t answer, “When it’s obvious it needs changing.” Gardening things are never obvious to me.)
    And if anyone else was wondering . . . 80 degrees Fahrenheit is about 27 degrees Celsius.

    • Karen says:

      Hi Natalie! The better quality your sweet potatoes the less you have to change the water. A cold damaged sweet potato will start to get cloudy, ucky water within 4 or so days. A healthy sweet potato’s water will stay clear for a couple of weeks. The only reason to change the water really is because it gets stinky and gross. I generally change mine if it looks cloudy and yucky. Hope that helps my little double black thumb. ~ karen!

  6. Nancy Blue Moon says:

    I would do most anything to see something green and growing right now…

  7. martina says:

    I put my sweet potatoes in the warmest place in my house but they ended up looking like this:
    Is that normal? They were delicious, but no sprouts, I’ll check again in 10 minutes.

  8. Suzy McQ says:

    Great posting. My only question is the removal of the plantlets from their mother sweet potato? Do they form roots and just are gently snapped off? I’m going to try this just as soon as I return North from sunny Florida. Sorry, couldn’t resist!

  9. Mel says:

    I’m so jealous and living vicariously through you all this year… I have a 9 day old baby boy and another boy under 2 and my gardens aren’t going to do much this year besides some carrots, rainbow chard and maybe a cucumber and tomato plant. I love your garden posts and look forward to them so much more than usual this year.

  10. Tigersmom says:

    We did this (sticking them in a jar of water and holding them in place with toothpicks) with sweet potatoes as a science experiment when I was in grade school.

    Unfortunately most of the things I attempt to grow end up being a science experiment. As in, how long will it take me to kill this living thing?

    I hope your sweet potatoes sprout and grow for you this year.

  11. Mary Werner says:

    My Mom always put the cut ends of sweet potatoes in water just like you described and we had drapes of sweet potato plants all winter which was weird and wonderful at the same time. She kept winding them around the top of a hanging basket and they kept growing until she broke off the vines and planted them which kept growing, etc., etc., etc. It was always green and fresh feeling in that room. I grew a bunch then broke the vines into many, many pieces (did not wait for roots) which I planted in the sandy bald spot in our front yard – hot, dry, where nothing grew. I watered and watered then slowly let up and behold I had the most amazing wonderful green (the leaves are the most brilliant green) stuff growing and I didn’t have to cut it like grass. They died in the winter and I dug up some roots and was amazed to find a huge foot long (round) bowling ball potato. Did not try to eat it! Here in Florida they grow like sand spurs! I don’t eat them either.

    • Karen says:

      That’s true Mary. You can just stick them in the ground without rooting! I should have mentioned that fact in the post. If you get to the point that the potato has slips but it’s already time to plant outside you can just stick them in the ground. ~ karen!

  12. Ella says:

    Im going to try this today, as I wait with baited breath for details on your seeds class tomorrow!

  13. Jody says:

    You’ve got HADD. Horticultural Attention deficit disorder……

  14. Turly says:

    I have never grown sweet potatoes to eat because I just don’t like them BUT cut one in half and plant the cut ends in a pot of soil and soon you’ll have two wonderful trailing creepers as indoor house plants.

  15. gloria says:

    Another horti-head here. I got so garden-starved in Feb. that I took 4 dry lima beans from their bag in the pantry and put them in a glass of water with a toilet paper tube to hold them against the side of the glass. Fast forward a couple wks. Roots. FF about 2 more wks. Leaves!! Roots and leaves got so big I had to put them in a pot of soil. Now I have bean vines so long they are latching onto the curtains in the window and could use a sturdy trellis. I fear they will take over the dining room before I can get them into the garden. We still have snow on the ground. Do you think these will actually produce beans?

    • Mary Werner says:

      Are you letting the pollinators in also? Horti-head, HA.

      • gloria says:

        Holy cats! I didn’t even consider the pollinators. I guess as soon as they start to produce flowers, and somehow I know they will, I will have to get them outside to meet their pollinating buddies. Thanks for the reminder, Mary.

    • Karen says:

      There’s only one way to find out Gloria … ~ karen!

      • gloria says:

        You’re right, Karen. Stay tuned for the next exciting episode of …
        Lima Beans, Will They Or Won’t They!!

  16. Auntiepatch says:

    It’s 90 degrees here in So. Calif. Please send SNOW!

    • Louise says:

      Yup, in my part of So. Calif. yesterday it was 93 degrees! But it will drop to 79 degrees on Tuesday (I hope!).

  17. Lynn says:

    Oh I would love to grow sweet potatoes , here is hoping I can get them to grow in my raised beds in zone 3 west of Leduc Alberta . Wish me luck I think I will need it.

  18. Becky says:

    I fear I also have horticultural head… I had some regular potatoes grow some really long chits. (I forgot about them in the potato bin) I put them in some ice cream buckets, with some dirt, and they now have leaves.
    Actual green leaves. I haven’t seen green leaves in months. MONTHS I tell you.

    Hopefully, withing the next month or so I’ll be able to get them planting outside.. otherwise they will outgrow these buckets reaaaaaaaally fast.

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