Beginner Gardening: When should I dig up my one plant potatoes?, 1 by hocasatown

hocasatown wrote:
I have never grown potato before, and I was happy to find one old potato I threw in the garden last year actually grew back this year and out of no where, there are potatoes all over around the plant. I didn't expect it to return and here it is, potatoes!

I am excited to dig them but when should I dig them up? and How?

I live in Portland and rain is coming soon so I don't want to leave them too long, they might rot.

Really appreciate your help.