Have you ever considered growing sweet potatoes (Ipomoea batatas)? Or have you always heard that they can’t be grown in Vermont, so have never planted any in your garden?
I tried to grow them a few years ago when someone gave me several sweet potato slips. Without any knowledge, I planted the slips in a circle in my garden.
When I dug them up in the fall, just before the first expected frost, I found what looked like spaghetti strips. Hmm. So, the next year my husband and I bought slips at my local garden center.
The experts at the center advised us to make sure the soil was loose so the plants could expand under the ground. So, we borrowed a small rototiller and loosened the soil.
We planted the slips in rows, a foot apart and in rows two feet apart, with a small amount of blood meal in each hole. Then we avoided walking in the actual rows until we dug them up in the fall.
Although sweet potatoes can be grown in all parts of Vermont, keep in mind that they need a three to four-month growing season for the tubers to form. They also need plenty of sun and well-drained soil. The vines grow above the ground and have very few insect or disease problems.
As a rule of thumb, wait until June 1 to plant as the soil needs to be warm, at least 65 degrees Fahrenheit. That’s typically at least two weeks after your last spring frost date. Sweet potatoes like water, and if there is a dry spell with no rain, you will need to water often. We have found that in rainy summers we harvested larger potatoes.
Knowing exactly when to harvest can be a bit tricky. If you planted in early June, you can probably start checking for tubers when the leaves of the plants start to yellow. The potatoes will be directly below each plant.
Dig them up carefully to avoid damaging the tubers. We use our hands if the soil is loose enough.
Be sure to harvest before the temperatures cool the soil as the tubers won’t continue to grow and there’s a greater likelihood of attack by wireworms and other insect pests.
We typically harvest ours in late September or early October, just before the first fall frost.
Tubers need to be cured in a warm room with high humidity for around two weeks to allow the skins to toughen. They will need to dry for about six weeks before they are ready to eat as this allows the starches to turn to sugar.
You can store them on a shelf in a dry basement with temperatures between 55-65 degrees Fahrenheit. The stored tubers will last until the beginning of next May, if you still have any left.
To save money, I keep a few potatoes every year, so I can sprout my own slips for the next season. Take a potato with a few eyes and put a toothpick in each side of the piece. Put it in a jar with water just up to the bottom of the potato. The potato will sprout within three to four weeks.
If you decide to start your own slips next year, the ideal time to start them is late April for planting in early June.
By Jean Parker, Extension Master Gardener, University of Vermont.