We've been growing sweet potato since June, and when we last dug into the soil (about a month ago), we dug up a sweet potato that was roughly the size of tennis ball. However, it was white and not the usual pinky-brown colour.
I've been told that sweet potato comes in different colours, and obviously there would be different varieties of it. So if I have the white variety, how do I tell if it's ready for harvest? Is it a matter of leaving it in the ground for a number of weeks/months, or can you tell by looking at the vines and leaves above ground?