A step by step guide on how to grow sweet potatoes & how to start slips. Growing sweet potatoes used to be a closely guarded secret among farmers. A mystical, mysterious process - like how to perfectly apply liquid eyeliner. Not anymore!
I've successfully taught thousands of you how to grow luffa in a cold climate (zone 6) and sweet potatoes (known as Kūmara where it's hugely popular in New Zealand) are no different.
It can be done and you can get a HUGE harvest even in a short season - you just need to follow the steps.
In 2010, when I first started growing sweet potatoes (Ipomoea batatas), there was almost no information on the Internet about it. At that time, growing sweet potato slips was a closely guarded secret in the farming community.
Not anymore.
Table of Contents
Two ways to grow sweet potato plants
🌱 It starts with growing the slips. 🌱
In order to grow sweet potatoes, you have to first grow sweet potato slips. These are the sprouts that come off of the sweet potato.
Every slip will grow into a sweet potato plant that will produce around 2 pounds of sweet potatoes
1. IN WATER
2. IN SOIL
Sweet potatoes sprout after they break dormancy just like the perennial plants in your garden do. These sprouts are called slips and they're what you use to grow sweet potato plants.
You can encourage your sweet potato to break dormancy by putting it in a warm room in either a glass of water or some soil.
Water Method
With this method you're generally safe to start your slips 6 weeks prior to when you want to plant them out.
STEP 1. Place sweet potatoes in a glass jar of water with half the sweet potato under water and the rest not. The part under water will grow roots and the part above water will grow slips.
STEP 2. Put the jar somewhere WARM - over 80℉ is ideal. Now you wait about a month for it to root and sprout.
STEP 3. Once the slips are a few inches long they can be pinched off of the sweet potato and rooted in water or planted in 4" pots.
STEP 4. Slips can be planted outside once the soil temperature is 65ºF (or 18ºC).
Soil Method
The soil method produces slips more quickly. With this method you're generally safe to start your slips 4 weeks prior to when you want to plant them out.
STEP 1. Place whole sweet potato(es) lengthwise in a pan of soil so the soil comes halfway up the side of potato.
STEP 2. Place the pan on a seedling heating mat.
STEP 3. Make sure the soil stays moist and wait for it to produce roots / slips in 2 weeks or less.
STEP 4. Once the slips are a few inches long and you can either put them in a glass of water to root, or plant them directly in soil to root. Either way is fine. Rooting in a glass jar takes up a lot less space than putting each slip in a 4" pot with soil.
STEP 5. Slips can be planted outside once the soil temperature is 65ºF (or 18ºC).
TIP! It's the warmth of the heat pad that speeds up the sprouting process.
How to plant
Sweet potatoes will be one of the last things you plant in your garden. They must go in later than peppers, tomatoes and other heat loving plants because sweet potatoes need more than just warm weather. They need warm soil as well as warm air.
STEP 1. Apply a couple of inches of compost to the top of your soil. You can also use a slow release fertilizer; I use Gaia Green's organic 4-4-4 all purpose fertilizer in my garden.
STEP 2. Lay black thermal mulch (plastic) on the planting area 2 weeks before setting out. Sweet potatoes need full sun so make sure your area has that.
STEP 3. On planting day cut a circle in the plastic and push one slip in. Make sure the slip has contact with soil all around. Repeat for all your slips.
STEP 4. Proper spacing for planting is 1 sweet potato slip per square foot. HOWEVER, I find spacing of 16" between sweet potato plants increases your yield & the size of your sweet potatoes.
STEP 5. Keep the plants well watered throughout the summer. Using the plastic eliminates the need to weed and helps retain moisture.
STEP 6. Harvest before the first frost. Once the weather cools down they won’t grow anyway.
* Speed up your soil warming by laying a layer of black thermal plastic in your garden bed. I use biodegradable plastic made of cornstarch that just decomposes on the soil by the end of the season. It will heat the soil up by as much as 10 degrees which means you can plant the slips 1-2 weeks sooner than if you don't use thermal plastic.
.
Growing in beds
Growing in containers
If you grow sweet potatoes in the ground you may find voles & mice get to them before you do. Hardware cloth can help with this. If you can't find it locally, Amazon carries hardware cloth.
- Cover your sweet potato bed with ¼" hardware cloth. Grow your sweet potatoes in a raised bed with wood sides. After laying your plastic down, staple hardware cloth around the edges of your bed.
- Plant the slips you have to punch a hole into the plastic with a pencil and push the slip through the hardware cloth, plastic and into the soil. THIS IS A PAIN. But it eliminates 100% of rodent damage.
I grow all of my sweet potato plants in containers.
- Plant 1-2 sweet potato slips in a 60 litre pot that measures 60 cm across.
- Remember to keep the pots watered as they'll dry out more quickly than a garden bed.
Once your plants are well established you can also harvest and eat the leaves.
Use them in: salads or cook them like you would spinach or chard.
This video shows my sweet potato harvest in 2016 after I tried using the hardware cloth the first time in a raised bed in my 40' x 40' community garden plot. In this video I'm using regular thermal plastic, not the biodegradable plastic.
How & When to Harvest
Near the end of their growing life sweet potato vines will start to yellow and croak. This is a GOOD sign! They're ready to harvest.
- Cut the tangle of vines away, leaving only a few stubs to let you know where the plants are.
- Using a shovel or digging fork, dig em up! Honestly, the most fun crops to grow are the ones that grow underground because you have NO idea what you have until the day you dig them up.
- Be careful when you're digging them and pulling them out. They bruise and break easily.
- Once they're all dug let them sit in the sun for a few hours to dry and begin the curing process.
If the vines get touched by frost and start to turn black the sweet potatoes can rot quickly so dig them up right away!
How to Cure & Store
Curing
Sweet potatoes need to be cured for 10 days in an area that is 85ºF with 85% humidity. Getting those conditions at home probably seems difficult but just get as close to those ideal conditions as you can.
Why do you have to cure sweet potatoes? Curing toughens the skin so they keep longer and it develops their distinct sweet flavour. A sweet potato dug straight out of the ground won't taste sweet at all! Try it.
Here's how:
- Put your sweet potatoes in a rubber bin with the lid offset so it isn't completely sealed off. Store this near a heat register, wood stove or sunny spot. This will create conditions as close to perfect as you can get in most houses. DO THIS FOR 10 DAYS.
- After the initial 10 day curing period move your sweet potatoes to an area that is between 55-60ºF for one month. This develops their flavour. After 1 month they will have developed their sweet potato flavour which will get even stronger as time goes by.
Storing
Store sweet potatoes in an area that doesn't get below 50 degrees in a container that breathes like a slatted wood box or a burlap sack.
How many sweet potatoes do you get per plant?
2 lbs or 4 sweet potatoes per sweet potato plant.
1 sweet potato plant will produce about 4 large sweet potatoes, or 2 lbs of sweet potatoes. Some varieties will produce 6 or more per plant.
The plant usually creates 1 very large sweet potato, along with a few smaller ones.
A single sprouting sweet potato can provide you with at least 15 slips (that's a low estimate). Those 15 slips will create 15 plants, which will give you around 30 lbs or 60 individual sweet potatoes.
Where to buy slips
If you don't want to grow your own you can buy potted sweet potato plants at many garden centres now and you can order live slips online.
Growing from store bought sweet potatoes
To grow your own slips all you need is a sweet potato that hasn’t been treated to stop sprouting which you can get at the grocery store.
How do you know if it’s been treated? You don’t. You go to the store, buy your sweet potato and hope for the best. Organic is your best bet for an untreated sweet potato, but both organic and "regular" store bought sweet potatoes have produced slips for me.
Tips on picking a sweet potato from the store to grow
- Check for cold damage. If the sweet potato has been exposed to below 55 degree temperatures it will probably rot rather than sprout. Cold damage presents with dark marks and lesions.
- Bigger isn't necessarily better. Small sweet potatoes, in my experience, have produced more slips than larger ones.
- Ask if they were grown locally. Locally grown means it will grow well in your region.
Sweet Potato with cold damage
Once you've established your very OWN crop of sweet potatoes you can use those for producing slips year after year.
Are ornamental sweet potatoes edible?
You may have noticed that your ornamental sweet potatoes also produce tubers. These tubers are edible but not delicious.
The good news is you can propagate ornamental sweet potato vine the same way as regular sweet potatoes! Just dig up the decorative sweet potato tuber in the fall, store it in a cool room, and then encourage it to grow slips in the spring. These slips can be planted directly outside or rooted and potted up for later planting.
Varieties of Sweet Potatoes
The most popular sweet potato variety by far is Beauregard and it'll be the easiest for you to find. But there are a lot more varieties than that.
- Beauregard* (best all around sweet potato variety)
- Georgia Jet (short season variety)
- Jewel (longer season but still doable in colder climates)
- Garnet (a purple variety with purple skin and flesh)
- Stokes (bright purple variety that retains its colour after cooking)
- Covington (a standard variety that grows well in cooler cliimates)
*this is the sweet potato I most often grow.
Note: I have successfully grown all of the above (with the exception of "Stokes") in my Canadian garden. I just haven't tried Stokes, but I'm sure it would be fine.
Sweet Potato VS Regular Potato
To clear up any confusion, sweet potatoes don't grow like regular potatoes. A regular potato is a tuber, a sweet potato is a root.
Regular potatoes are grown by planting whole "seed" potatoes into the ground. (here's my guide on how to grow regular potatoes)
Sweet potatoes are grown by planting only the sprouts aka slips that grow from the sweet potato.
The Start to Finish Guide to Growing Sweet Potatoes.
How to successfully grow sweet potatoes whether your garden is big or small.
Materials
- Glass of water
- Foil pan with soil
- A sweet potato
Tools
- Heat mat
Instructions
- Start sweet potato slips 6 weeks prior to planting out.
- Rest a whole, undamaged sweet potato in soil and set on a heating mat. Slips will start to grow in around 2 weeks. When around 5", break slips off of sweet potato and plant out or root in water.
- Rooted AND unrooted slips can be planted directly in the soil.
- Speed up how quickly you can plant your slips outside by laying down thermal plastic
- To prevent vole/mole/mouse damage either grow sweet potatoes in very large pots or grow in a raised bed with wood sides and ¼" hardware cloth across the top.
- Dig up sweet potatoes when the weather cools in fall.
- Cure sweet potatoes at 85F and 85% humidity for 10 days.
- Cure another month at 55-60F allowing potatoes to develop sugars.
- Store long term in vented crates or burlap bags at no colder than 50F
Sweet potatoes can be harvested 4 to 5 months after planting.
You get around 4 sweet potatoes per plant. Usually one very large one and a few smaller but still substantial ones. Some varieties under the best conditions will produce even more.
Any potting soil will work well. It has the nutrients you need. If you are reusing potting soil you'll need to amend by adding fertilizer. Adding a 4-4-4 fertilizer or a few inches of compost to the top of the depleted potting soil will revive the soil. I also use native garden soil in my sweet potato containers.
Yes, that's exactly how you grow them but you don't plant the entire sweet potato. You let the sweet potato sprout in a warm place, pull the sprouts off when they're a few inches long and then root or plant those in soil.
May or June are the best months to plant sweet potatoes outside when the soil at planting depth has warmed up to 65ºF (or 18ºC).
Yes! Sweet potatoes do really well in beds, buckets or pots. Buckets and pots are especially good for growing sweet potatoes because they keep the soil warm and prevent moles and mice from eating the growing tubers.
Once you have a whack of sweet potatoes that you've grown yourself, if stored in good conditions, they'll last you into April or even May.
You can turn them into my personal favourite guaranteed crispy Sweet Potato fries with a Sriracha/mayo dip, Sweet Potato soup or sweet potato casserole.
Now go forth and grow.
→Follow me on Instagram where I often make a fool of myself←
Kelly
A few more questions! Would setting the tray on a heating vent in my house work in lieu of a heating pad? House is set to 70F. Have you ever tried growing Carribean sweet potatoes (purple skin, white flesh)? Not sure if our weather here in Hamilton would support that variety??
Karen
You can give it a shot, but the problem with a heating vent is it's inconsistent. If that's all you have though, then by all means give it a shot. I also worry the heat that comes out of the vent would actually be to warm and would also dry out the soil in the pan very quickly. If you're in Hamilton, Home Hardware sells the seedling heating pads. I think they're about $20. ~ karen!
Kelly
I can't wait to get started! Just need to pick up a heating pad. We typically grow potatoes here, but two of us have a nightshade allergy and eat sweet potatoes instead. Do you have any advice on how many slips or how many square feet of garden to use for a family of 4?
Karen
Hi Kelly. It all depends of course on how many time a week/month you're going to eat them, but I would say growing a 4'x 4' plot of them, which amounts to 16 slips would do you. I have however, found if you plant slightly less in a 4' x 4' area (12 slips instead of 16) you actually end up with bigger sweet potatoes. ~ karen!
Paula
So you use actual soil and not the 'soilless' mix used for seeds? This maybe a dumb question but I would rather check now before I start the process.
Karen
Yes, actual soil Paula. I also mixed in a lot of compost. ~ karen!
Thandi
I accidentally got sweet potato slips once. Apparently the back of my grocery cupboard was not only a great place to lose a sweet potato, but also a very comfy place for that sweet potato to send out some happy little tendrils. I kept it on a saucer in my kitchen window, named her Sweety Potato, and misted her every few days. She was a great friend, dear old Sweety Potato, enthusiastically growing on her little saucer in the sun. But then we went on holiday and when we came back she was no longer with us. I miss that silly cupboard plant.
In other news, my husband has suggested that I stop bloody well naming things, because I get emotionally attached to weird stuff.
Karen
LOL! Awwww. Sweety! ~ karen
Linda in Illinois
I have never grown sweet potatoes, do you just purchase one from the grocer and then plant it?
Marti
So... on the "please be my stooges who find a cool chair for me" post, there was a video on the side.
But on this post, it's gone again? I had almost gotten accustomed to hearing you talk to me while I was trying to read that entire post. But it was a "one-time-trial-event"?
I quite liked it, but think you might goose the audio just a little more. I have really good hearing, but even with the sound on this chromebook all the way up and the sound on the link all the way up, it was having to strain toward it.
How many slips do you get per potato?
Terri J.
Still having trouble reading your posts. Putting something so wonderfully originally funny such as "Pinterest people" at the beginning of your post makes me ROFL (had to use that even though I really hate those inital things) so hard it delayed my reading the entirety of your writing. BTW keep up the good work.
Vaalerie
In lieu of a plant heating pad, just a question. Do you think an ordinary heating pad set on low and on a heat resistant surface such as the top of my stove would be an acceptable alternative? I have two (people) heating pads and hate to purchase a plant heat pad if I don't have to.
Karen
Hi Valerie. I can only recommend personally, the seed heat pad since that's what I've used. But I can say I definitely know people who use a waterproof heating pad on low. You have to be careful that even on low it isn't too warm, and also that your heating pad doesn't automatically turn off every few hours. Many of them do as a safety feature. ~ karen!
Chrissy
Vaalerie, I put Christmas lights under my seedlings using an overturned tray that I place the seed pots on top of. You can't use LEDs, only the older ones that produce a little heat. I keep a thermometer nearby and adjust the temps by using a timer with the lights so I don't bake the plants. Works very well if you don't want to spend on a seed pad.
Gilly Bean
Clever! I love that. Thanks. <3
Gilly Bean
Would this work for NOT sweet potatoes? I'm not a fan of sweet potatoes but, would like to grow some other varieties of potato that aren't the regular brown and white ones....on the other hand....maybe I could give one to the family member that is inviting me to Thanksgiving and Christmas dinner.... ;-) ...well, two in that case. Probably more if I grow them successfully. Either way I'd like to try to grow other types of potatoes and wonder if this method would work for them too.
Karen
Hi Gilly Bean. Growing like this wouldn't work for other potatoes. Sweet Potatoes aren't actually a potato and in fact are a member of an entirely different plant family. Sweet potatoes like heat. Regular potatoes do not like heat at all. Regular potatoes are planted outside as early as March while sweet potatoes can't be set outside until June at the earliest. ~ karen!
Elaine
As one of your other readers said, Karen, I enjoy reading all of your posts ... even when it's something I can't do. I'm in a condo now that faces north and north-east, receiving sunlight until around 1:30 p.m. However, I LOVE seeing things sprout and have a very green thumb so I might try this purely for decorative purposes. Maybe my balcony pots will display sweet potato vines instead of Boston ferns this Summer! Thanks a lot!
Karen
You're welcome! ~ karen
Kathy
You sound really excited and then so am I so I need to plant sweet potatoes. I really like eating them so that's good. But I buy sweet potato vine plants because I like the light green foliage so will I get a beautiful vine and potatoes? I suspect the store bought vine is something different.
Karen
Hi Kathy! Yes, sweet potato vine that you get in the nursery is different than an actual edible sweet potato. I'm with you though, I love the lime/bright green foliage on the nurser ones! When you dig the ornamental ones up at the end of the season they do in fact produce some type of sweet potato, but it's not the kind we produce for eating. (although it could very well be edible) ~ karen!
Beth
The ornamental sweet potato vines are non-toxic for people. But they are poisonous for cats, dogs and horses. However! Their seeds ARE toxic for people. So don't eat the seeds. And don't let pets nibble on the vines.
Shellie
This may apply to ornamentals, but not sweetpotatoes grown for consumption... see the aspca website... they say non-toxic for dogs, cats, and horses.
Jenifer
Just need the pan and some soil...and a place to put it without the cat thinking it's her personal play ground (or, god-forbid, a new litter box!)
Wish me luck!
Jennie Lee
You just provided me with the perfect place to leave my comment, Jenifer! We're both Jen(n)ifers, too- how serendipitous! Sweet potato plants are toxic to both cats and dogs. I have a cat, and I'm always careful to look up any plant before I bring it into my home, to make sure it's safe. It's easy to look it up with Google. The ASPCA list is the most complete. They give info for cats, dogs, and horses! They also provide lists of NON-TOXIC plants, which is very reassuring, since if you don't see a plant on the toxic list, how do you know if it's really safe, or if they just omitted it accidentally? I'd advise putting the plants up high or in a room the pet can't enter= and don't let leaves fall off, to the floor!
ronda
I would think soil and heat are the winning combo. For any plant! Probably why my rose slip had a couple of beautiful little green leaves one day and dead and dried out leaves the next. Just when I was thinking I should get the bag of top soil out of the garage, they were done for.
Mary W
Karen, you are always a welcome click to a moment of morning de-stressing. Going to get my cat warmers and hopefully grow several big pots of sweet potato leaves for my porch.
Karen
Hi Mary W! Glad to help out! :) ~ karen
Mary W
I have two cat bed warmers for my outside cats. They heat up to "cat temperature" and will work wonderfully to start the slips. Better than storing the beds now that spring is here.
Maureen Locke
Karen, did you break the internet again??? Your link to the heating pad doesn't work.. none of them. I tried them all. So, I went to amazon.ca and can't find a heating pad that's $16.99 either. Not sure when/if I'll be growing sweet potatoes but I want to be ready when I do.. lol
Suzanne Reith
With such iffy a timeline, how will I know when to start. How long can you keep them before setting out?
Karen
That's the problem with the initial method Suzanne. I normally start my sweet potato slips in March and everything usually works out fine. This second method with soil and a heating pad has so far been quite reliable for me so now I can start them much later, knowing I won't be planting them out until June 1st. As long as you can keep them alive in your house they'll be fine to plant out at any time as long as you properly harden them off. As the sweet potato slips grow you can just break them off (as I show you in the original post), root them in water and plant them in separate pots. The original sweet potatoes that are growing the slips will continue to produce slips indefinitel so you can keep making multiple slips.. ~ karen!
Suzanne
Thanks Karen. Looks like I'm in business. All those vines, and a sweet spud bonus. Can't wait for summer. Glad too, that we got this comment problem sorted.
Meredith Mustard
Hi Karen,
I really enjoyed your story. I couldn’t figure out how to write a comment to you so here it is.... I live in Pennsylvania near Philly and I tried growing sweet potatoes in the bro-under with zero luck. I think the warm soil season was just too short. Since I moved to a small house and was not sure how long I would stay here I decided to have an experimental garden plabnted into hay bales thus avoiding building containers which I prefer to garden in. The theory is that you feed the bales with high nitrogen fertilizer for a few weeks before growing season watering them generously not encourage the growth of compost producing bacteria. I did just that and had a fabulous productive vegetable garden that was also low maintenance. BUT the problem I ran into was I outlined my little south-facing cement porch with bales of hay, hoping to grow flowers in them. The seeds sprouted but disappeared so the bales were bare. I noticed a sweet potatoe on my kitchen table had sprouted so I cut it into 4 chunks and dug them into the bales out front expecting the vines to make a lovely statement while disappearing the unsightly bales. They did the job quite quickly and covered the whole porch. Good Job! When the first hard frost came I thought I must remove the vines before they discolored the porch cement. Low and behold! When I started pulling up the vines along came oodles of sweet potatoes! There were about 7 of them as large as a football. It’s was easy and amazing. I probably harvested 50 lbs of sweet potatoes from that one potatoe without having to plant sprouts. And they were so easy to harvest from the bales since they were not locked into the soil. I think the secret to my success was the heat absorbed from the sun beating on the bales. EASY!
Leslie Zuroski
Would this work for me who only wants to grow them for ornamental purposes?
Mary W
I just cut up a couple of sweet potatoes and buried them in the ground all over my front yard, hoping to give up mowing since I love ornamental sweet taters, too. It worked like a charm for about 6 months, then they got mowed by my daughter's new husband that LOVES to mow grass. So sad but they do grow like weeds in Florida. They also have special varieties that produce an over abundance of pretty leaves and fewer potatoes for those of us that love the foliage.
Karen
Sure. The sweet potato doesn't know if you're growing it to eat or just to look at. :) ~ karen!
Nicole
I bet these plants from the dirt/heating pad slips grow larger than the water ones and have more sweet potatoes, given how much healthier they are from the starting line! But much like TucsonPatty, my talents do not lie in gardening. I garden vicariously through you. :)
Sheryl
Your blog entry's are so much fun to read. I read them even when I'm not interested in what you wrote about. And your links to other posts? I think you have set some very effective time traps. I'm thinking of quitting my job just to have time to drift from link to link. I won't even mention how much I enjoy your photos. Oh wait, I just did.
Karen
Sorry Sheryl, don't mean to send you down a time warp of posts, lol. Well, actually I kind of do, but it sound rude for me to admit that that's my goal. :) And thanks! ~ karen!
TucsonPatty
What a font of Sweet Potato slip information. I don't grow anything (except brown leaves...) : ( but this makes me want to do the whole Sweet Potato in the glass trick that we had when I was a kid. I remember it on top of the heating stove, and it grew like crazy!! I should have told you the heat trick before! If only I had known what was happening. ; ) I did eat my Sweet Potato Fries tonight, like a good tater fan.