After searching TMG and not finding the answer to his question about sweet potatoes, friend and reader, Jim, from Illinois sent the following question to me:
–I heard that sweet potato vines will want to send down roots (from the vines) if the soil is moist, and that you should gently pull up the vines every so often to check that these vines are not setting down roots which will significantly reduce your potato yield. The only place roots should form is at the parent plant.
This is the first year I’m growing sweet potatoes and I just wondered if you have any experience with this? I can see how this would kinda make sense, but also wonder how additional roots can be a bad thing??
Replying to Jim, I told him that in all my years of gardening I’ve only grown sweet potatoes one year. I had no room in my garden that year and tried them in a flower border. The voles got them all.
Turning to a Long-time Friend and Gardener for the Answer
Fortunately, I have a friend whom I knew would be able to answer the question. My long-time friend, Charles, grew up on farm and has gardened for more than 50 years. And he knows his stuff. And when he visited me today, I was ready with Jim’s question.
Charles said when he was a kid growing up they use to cut off the running sweet potato vines and feed them to the livestock. He said the supposed purpose was to make use of the vines and at the same time not allow them to root and take energy away from the main plant that was producing the sweet potatoes.
He was quick to say that they never tested the “theory” — but that’s the how and why of how they handled the runner vines on the farm years ago.
So evidently what Jim heard or read goes back many, many years.
At the beginning of the growing season Charles continues that practice even now until he gets bogged down with other chores as the season progresses. Then he just lets them grow and do what they want.
No Sweet Potatoes Form Where The Vines Root
This long-time gardener also pointed out that where the vines root, no sweet potatoes form there. HOWEVER, if you cut the vines away and transplant the section of the plant with the new root, it will give you sweet potatoes! (As I type this, I’m wondering if you could just cut the new root off from the parent vine and let it grow in place by itself and get potatoes?)
Starting Your Own Sweet Potato Slips
Most of us have seen someone put a sweet potato in a jar of water and have it put out shoots (slips) which can be transplanted to the garden.
Charles suggested a way to start slips that is much more to my liking and he said the soil in my garden would be perfect for this method. (Be sure to use sweet potatoes that have not been sprayed with sprout inhibitors as those at the grocery store are.)
The number of sweet potatoes you use will depend on how many sweet potato slips you want to grow. Each potato will give quite a few slips. Better have more than not enough in my opinion.
Once you have the potatoes, plant them horizontally about 4 inches down in good garden soil in late winter once you know the ground won’t freeze again. He suggested late February or early March here in our area (Virginia – zone 7).
When nature gives the potatoes the right cue, they’ll send up sprouts. You can lift those up and transplant them to start your sweet potatoes. Plant as many of the sprouts as you have room for. (I’d guess about 18 inches apart.)
Other Things Charles Has Shared With Me In the Past
By the way, I’ve mentioned things Charles has shared with me before. Long time readers will recall the story about Charles pulling up tomato plants on the farm and hanging them in the barn allowing those green tomatoes to continue to ripen long after frost.
Another story about potatoes and voles is in the book (Organic Gardening, Cutting Through the Hype to the 3 Keys to Successful Gardening) on page 221.
If you’ve raised sweet potatoes for years, why not share some of your expertise with rest of us in the comments below.