hi
i've got various potatoes growing, mainly in compost bags. I noticed today that the stems of one of the plants wasn't looking at all healthy so decided to harvest some out of that bag. The potatoes themselves seem ok, but some of them have black bits several mm across on the surface of the potato skins. It's not soil, and it doesn't appear to be a living bug of any kind, and it seems to rub off and the potato skin under these black blobs looks normal - can anyone tell me what it might be? and whether this affects what we can do with the potatoes? should i fully harvest the rest of that bag?
ps not grown main crop before - when are they best to harvest? some of the ones i pulled today are a bit on the small side, and whilst there are some nice sized ones, none are at the sort of size i'd want for jacket potatoes etc...
thanks L