Planting sweet potatoes doesn’t happen till well after the last average frost date, but if you want to grow your own slips/seedlings, you need to start 8 or 9 weeks earlier. For Zone 6b we start our sweet potatoes mid-March. All you need is one or two sweet potatoes and jars of water to grow enough slips for your home garden. I used some small sweet potatoes leftover from last fall, but I have successfully grown them from store bought sweet potatoes in some previous years. It doesn’t always take 9 weeks, so if the calendar says you should have started them a few weeks ago, go ahead and start one and see what happens. Kids love to watch the process of growing the slips.
My tiny sweet potatoes had just started growing little leaf buds, so I went ahead and prepared them to root. I started several because I wasn’t sure how many slips the little ones would produce. If I have to buy sweet potatoes to grow slips, I’ll buy one or two medium size from the grocery store. Once the vines start growing, they grow fast and it won’t be long until you have plenty for yourself and maybe to share.
Examine each sweet potato to find the end with the most eyes (little dimple-looking spots). That will be the top sticking out of the water. I stood the tall thin ones up in tall narrow glasses. I inserted 3 toothpicks in each of the small fat ones so that the toothpicks would hold them halfway out of the water. Set them in a bright or sunny window.
Since I really don’t have room to set the jars any place without having to move them frequently, I used the tall thin glasses and cut off water bottles to fit into an old wicker silverware and paper plate holder. Now I don’t have to worry about either moving or knocking over those little bottles. It works like a charm!
Keep tabs on your sweet potatoes and make sure there is enough water that the bottom half of the sweet potatoes (and future roots) are submerged. Mine started putting out roots in a week, but it can take up to a few weeks. Little leafy vines will start to grow out of the top. I let mine get about 4″- 5″ tall before I carefully break the little slips off. Put them in another jar of water to root, just like you would a houseplant cutting.
Each little slip will root and that will be your sweet potato plant. If and when your rooting slips start getting too long, cut a few inches off the top end of the vine 1/2″ or so below a leaf, remove the leaf and put the stem cutting in a jar of water. There needs to be at least one leaf left on the stem.
After just a few days, three of the seven pictured in the top photo already had 4 slips growing and the other four had 2 each. And after three more days, the sweet potato below is the same fat little sweet potato on the left in the picture above and now has 6! I just put it in the larger jar for the photo so you could get a better view.
Unlike regular potatoes that grow up from the seed potatoes and you have to keep piling soil on them, sweet potatoes grow down. They are formed from the roots “swelling”. If you are planting in the garden, plant sweet potatoes in good garden soil in holes 6 inches deep about 12 to 18 inches apart. Bury the slips so that just the top leaves are exposed above the soil and try to make sure the slip roots are straight and spread out when planting to avoid gnarly-looking sweet potatoes in the fall. Allow 3 feet between rows to allow plenty of room for the vines to run. One problem with letting the vines grow and spread on the ground, is that the vines will root and grow more sweet potatoes, usually resulting in smaller sweet potatoes.
You can also trellis the vines upward and if you are growing them in containers, the vines could be a privacy screen or provide shade on the patio. The picture below is our sweet potatoes from last year in the two white containers. We tried out larger containers last year, but it didn’t improve the harvest any.
In Zone 6b, the rooted slips are planted in early June and generally need 90 -120 days to grow. I think some go up to 170 days, but our summer season isn’t that long, so I stick to the lower day range. One plant averages 2-3 sweet potatoes per plant, but it all depends on the soil type, moisture and fertilization. There are pretty Morning Glory-looking flowers late summer and when a lot of the leaves turn yellow, it’s harvest time! After digging up the sweet potatoes, they need to dry for a few hours in the open air, then cured for 6 – 10 days in a well ventilated area such as a shed or garage. The area needs to be warm (about 85°) and humid (90 to 95 % humidity). This will convert the starches to sugar which increase the sweetness, heal any damage done while digging, and toughen up the skin.
Don't rinse the sweet potatoes before drying and curing.
When ready to store, just brush the dust off of them.
I’ll do into more detail and show you how to grow sweet potatoes in containers in a May post. Yes, it can be done successfully, and they are so much easier to dig up!
I found this source of sweet potatoes for you, if you’d like to order your plants online, or even to just read about the different varieties .https://www.sweetpotatoplant.com/our-sweet-potatoes/