Honestly, the whole 'big pots for big roots' thing never worked on my balcony
I was at a garden show in Portland last spring and saw a guy growing huge peppers in these shallow, wide containers. He said he switched after his deep pots kept getting waterlogged at the bottom. I tried it this year with my bell peppers, using a 12-inch wide but only 8-inch deep planter. Tbh, they're the healthiest plants I've had in three seasons. I think the soil dries out more evenly up here on the 4th floor. Has anyone else had better luck with wider, shallower pots for veggies on a balcony?