The coolest thing about growing potatoes in planters is that you can keep a close eye on them. I’m going to let them go until they flower, but for now, I’m checking for new potatoes close to the surface. Lots of gardeners say that this is fine to do as long as you’re careful and don’t injure the plants.
I didn’t want to dig too far, so I stopped when I got five egg-sized spuds.
Here’s a video, in case you want to see how I did it:
Charlie's Garden 