For sweet success in harvesting these tuberous roots, here’s when to dig them up

It’s nearly October, so now is around the time to head out to your garden and dig up this year’s bounty of sweet potatoes. This year has been long and hot, which, fortunately, are the conditions these tuberous roots require to flourish. So how should you harvest them? And how do you know when they’re ready?

One handy trait of sweet potatoes is that unless they have a disease or pest issue, they can continue in the ground from when they are planted until the season’s first freeze. This makes knowing when to harvest them exceptionally easy, as all you need to do is watch the weather report. Knowing that the roots are incredibly tender and will not respond well to frost, you will want to get them out of the ground before this event happens.

While the size of a sweet potato does not affect its quality or taste, you will want to harvest your roots sooner if you aim for a smaller to mid-size crop. Football-sized harvests may not be beloved by chefs. In this case, mid-September to mid-October is your window for harvest, and the only true “tell” is to either dig a plant up and check the size or look at the height of the mound forming at the base of your vines.

When harvesting, aim to either remove the vines or pull them back so you have a visual of the digging area. Then, using a pitchfork, gently dig the plants up. Begin from the perimeter of your plant mound and work your way inward. Like Irish potatoes, sweet potatoes will primarily form in clumps at the center of the plant, but they should be dug gingerly so you do not stab through your harvest or rip the skin of the potatoes.

Out of the ground, know that your sweet potatoes will require a curing time to set the skin and make them suitable for storage. This will also allow them to develop a better flavor. Contrary to Irish potatoes, sweet potatoes prefer warm storage and will decay in the cold. To cure, store your harvest in a ventilating container like a cardboard box in a warm, humid environment for up to two weeks.

Ideally, the curing area will be 85-90 degrees with high humidity. If, however, you don’t have the means to replicate these very specific conditions, a warm shed or garage, or outside in the shade, can also suffice. Given that sweet potatoes have delicate skin as well, it may be best to avoid washing dirt from the crop until after curing. If you do wash the crop after harvest, be sure to dry it thoroughly to prevent mold or rot.

Also, the roots of your ornamental sweet potato vine are technically edible, though they probably won’t taste that good. These varieties have been bred specifically for their ornamental traits, not flavor.

Anthony Reardon is a horticulture agent with Kansas State University Research and Extension. Need help? Contact the Johnson County Extension gardening hotline at 913-715-7050 or email garden.help@jocogov.org.