This year will be our second season growing sweet potatoes. The first time I grew them was on a whim, because I love them so much. I vaguely remembered an old flat mate of mine had accidentally sprouted one that she’d left out on a counter, so I figured I’d give it a shot. To my delight it was a fun and rewarding thing to do. I hadn’t raised my hopes too high in case it had all gone wrong. The plants are absolutely gorgeous, so even if you don’t end up getting any tubers, it’s still a lovely addition to a garden.
Sweet Potato Climate
Sweet potatoes originated in Central America and so are much happier in warmer wetter climates than mine here in Canada. In Ontario, growing sweet potatoes is a bit of a challenge but definitely not impossible. The trouble in my area is that sweet potatoes require a nice long, leisurely, and warm growing season. This is not really possible just by planting out after our last frost date. (Which is normally something silly like May 15th!) With a little bit of help from us and a good head start, we are hopeful to have another crop this year.
Slips not Seeds
It is pretty uncommon to grow sweet potatoes from seeds. The common practice is to use vine cuttings (Fun Fact: sweet potatoes are related to Morning Glories!), or from little growths called Slips. Slips are just the small sprouting vines that grow off the tuber itself if left somewhere warm and bright during storage. Since I have no access to a productive vine to get a cutting from, starting ours from slips has been the easiest. And it’s a fun and easy bit of gardening to start very early in the winter if you have that itch!
A Long Season
Tubers on sweet potato vines need a very long season to grow and do not tolerate frost. Here in Ontario our Frost Free time of the season tends to range from about May 15th to about October 15th. 5 Months is not really long enough. So you should first figure out your frost dates, and give yourself a solid head start to when you plan on planting out. This year, I got my slips started around the beginning of February. And I probably could have started them even earlier then that.
To get started, the first thing to do is to buy a sweet potato. Do your best to buy a good sized organic one, and if you can, one that has been grown close to you. Make sure you have a pretty warm and bright place for these to get started. I use grow lights and and shelf in a cozy part of my living room, before my other seedlings get started. You want about 12 hours of light and an average temp of about 22C(75F).
For this, you will also need two wooden skewers, and two cups or jars with wider mouths than the fattest part of your potato.
Cut the potato in half. Cut each skewer into 3 equal parts. What you’re going to do is stab 3 pieces of skewer into your first potato half so that it can be suspended cut side down into your jar or cup. To do that, stab your first skewer piece into the side of your potato about 3cm (1.25 inches) above the cut edge, and about 1cm (~0.5 inch) deep into the flesh. Repeat this twice more into your potato at thirds around the outside. This should allow your cut edge to hang down into the jar. Repeat the whole process with your second potato half.
Fill the jars with water so that the potatoes are submerged. Place them in your chosen warm and bright place. Now you play the waiting game!
Waiting For Sprouts
Depending on your potato, and the environment in your home, the wait will vary. Keep an eye on your potatoes to make sure they have water. And within a few weeks you should see little nubs starting to poke out of the sides. This year mine sprouted in about 2 weeks.
For the following weeks you will continue to nurture your little nubs as they grow and start to get leaves.
I usually wait a good long time before cutting the slips off. I wait until a slip is about 10cm (4 inches) at least before cutting it. At that point it will have a lovely little collection of leaves that will broaden after you cut it and let it root.
Cutting the Slips
Using a very sharp knife or a pair of good scissors, cut the slip off the potato right at the base. Place the cut slip into a new cup of water and back under the light. You can simply put it into water, but since mine ended up in my little growing shelving unit and things get moved around in there, I filled the bottom of the cup with hydro beads (pebbles are perfect for this) to keep the slip standing. Both methods are fine. The next waiting game begins.
Keep on Growing
Again, monitor your newly cut slip for watering over the next few weeks. You will start to see roots growing quite quickly at this point. But, it’s a good idea to let the roots really develop at this point. Early stages of root growth are susceptible to dehydration. Letting them get nice and strong in the cup of water, gives them a better chance further along.
After about 3-4 more weeks, you will have a wonderful collection of roots. Your vines will also be leafing out nicely. Now you can transfer them to soil! In a few weeks they will be big enough to be planted out after the frost.
Transplant to Soil
If you used pebbles or hydro beads to support your slip, gently tease the roots away from them. Have a good sized pot ready to go with a nice easy draining fertile soil mix. Dig a small hole into the center of the pot and place your root ball and the first few cm of stem into the hole. Gently pack soil down around it, just enough the cover and keep it sturdy. Water it thoroughly, and place it back in your warm sunny spot, and watch it grow!
Make sure you keep an eye on the humidity of the soil. Sweet potatoes like an evenly damp soil. So do your best not to let it dry out causing you to flood the pot to compensate.
Once all signs of frost are gone, go ahead and plant those beauties outside in a warm and sunny place.
It is currently too cold here to do any planting out. So this is where we have gotten to in our sweet potato adventure this year. I will update this post when we have planted them out and again when we start to see a harvest. I can’t wait to hear your sweet potato stories. Best of luck if you are also living in a colder place!