Today we are digging sweet potatoes. You can start digging them as soon as you like the size...Vivian likes small ones and so does Langley. Harvesting is usually about three to four months after you plant the slips. The leaves might be turning yellow, but we've had so much rain lately (Hurricane Joaquin) that the colors are muddy. You can also leave them in the ground until the first fall frost.
The roots will have spread about 4-6 inches into the soil (ours is sandy/loamy) and so you might want to use a spade fork to dig. Warren uses his hands. Be careful since the potatoes bruise easily.
After you dig them up, shake off the excess soil but do not wash them. They will need to cure...this forms a second skin that forms over the scratches and bruises. Lay them out so they do not touch. Keep them in a warm place (about 80 degrees) at high humidity (about 90%) for 10-14 days (Warren says for a couple of months!). The roots should last about six months if you keep them in a cool place (about 55-60 degrees). (Thanks to almanac.com!)
Be gentle with them! Langley adds orange juice, nutmeg, cinnamon, brown sugar to cooked and mashed potatoes, and then covers them with tiny marshmallows and browns them for Thanksgiving goodness!