I’ve only grown sweet potatoes a couple of times in the past, so I’m still learning the ins and outs of how to best grow and harvest this crop. We planted 2 rows down the length of each of two of our beds, with slips a foot apart. Our 50-square-foot garden beds are 18 inches high, about 3 feet wide, and 16 feet long. We ended up with 2 rows of the Covington variety in one bed, and one row each of Covington and Vardaman in the second bed.
I didn’t want to risk having the sweet potatoes damaged by frost, so we scheduled the harvest for the first week of October, before the date of our average first fall frost.
Then, to make the harvesting easier, we cut all the vines off the roots, and removed them from the bed. The tubers had grown several inches above the soil, as well as nearly a foot below.
We used a spading fork to carefully lift the tubers from the soil. This is much easier to do with larger raised beds. Last year, I grew sweet potatoes in small 3′x4′ 8-inch high beds. There was no room to use a spading fork – so we had to dig them out with a trowel! This proved very difficult, as the tubers grew very deep, into the heavy clay soil below the raised beds.
Fresh sweet potatoes are extremely fragile, and bruise or break easily. Never throw or drop the tubers – set them down carefully. These are brand-new garden beds, and we didn’t know what to expect – but it sure wasn’t digging up 120 pounds in this single 50-square-foot bed!
We were surprised and disappointed to discover extensive damage to the surface of the tubers. This had not happened the year before. After doing some research, we discovered that it was caused by the very large grubs of the June beetle.
However, the grubs only affected one of the two sweet potato beds. The second bed was invaded by chipmunks instead – digging tunnels, and feasting on the tubers, both above and below the surface. Fortunately, they caused less damage than the grubs. We’re still not sure why the grubs only attacked the one bed, but we suspect that the two batches of soil we purchased when we built these beds this spring came from different sources.
We were quite amazed at the size of the Covington tubers. After all, our garden is located in zone 6B in the mountains of southwest Virginia, and we do not have a long, hot climate.
We also grew a bush variety with shorter vines called Vardaman. It has great flavor, and (if properly cured) stores all winter long in a cool room in our house. These tubers are much thinner, but delicious.
You need to cure sweet potatoes properly before storing them. Keep them out of the sun, and cure them with temps in the 80′s and high humidity. We use our spare upstairs bathroom to cure our tubers. It has a closet with several shelves that can hold over 100 pounds of sweet potatoes. We have a separate heater in that room, so we set the thermostat around 83 degrees, and ran a hot shower for a few minutes a couple of times a day to increase the room’s humidity.
After 10 days or so, you can store them for the winter. We keep our tubers in an unheated closet that usually stays between 55 and 60 degrees. We can usually keep eating the tubers throughout the winter, well into April and May, even after they start sprouting.
Note from mid-April 2013: Nearly all of our sweet potatoes have stored very well, despite all the damage from the grubs and chipmunks.