Last spring was the first time I had ever grown potatoes - I didn't know what to expect. I watched an empty garden, what was going on below ground. Eventually they began growing - I was so excited. After a while I started wondering when I could dig them up. I was told that when they were blooming, you could harvest "new" potatoes. I waited and waited but no blooms - I heard that sometimes they don't bloom - so I started digging. We ate a lot of new potatoes last spring, before torrential rains came and ruined the potato crop.
This year is different - I've got raised beds which means no flooding, and I've got three kinds of potatoes and my red ones are blooming. It really surprised me, since none of them bloomed last year, but those are the only ones. I don't know whether or not the others will - we'll see.