I grow my food here in MA zone 7b. I always used to try to get my potatoes in around St. Patty's day but one year I was nearly a month late. I observed that it made no difference! The warmer it is the faster they grow, so now I don't worry or rush it. Same is true for snap peas. I buy seed potatoes because there is less chance of disease but if some bought for food sprout they get planted too. I try to pick the smallest potatoes with the most eyes, I don't cut them. I dig a hole roughly a shovel's length deep and press the potato into it but leave the top, with eyes facing up, sticking out. I check my garden every day or so and when I see leaf growth I push some dirt back into the hole to just barely bury it. I repeat this until the soil is level again. My plants are usually very large and bushy and I usually get 6 to 12 potatoes, sometimes more, from each plant depending on variety, I grow Red Norland, Russet, Yukon Gold, Superior, Russian Banana and red fingerling and this year I'm trying a bicolor fingerling. I too have volunteer potatoes, little ones I missed the previous year, coming up all the time so now I am experimenting with a permanent potato bed, I put any and all potatoes that overwinter in it and only dig them up when I have a really nice big plant show up. I always put the smallest ones back in. So far so good I have maintained this bed for 3 years now.