Everyone tells me to use big pots for root veggies, but my balcony carrots grew huge in tiny containers instead. | Balcony Veggie Gardens - Topic Shares
How deep was your soil mix though? Mine did the same thing last year in those shallow window box planters. I used a really loose potting mix with extra perlite, watered them almost every day in the heat. The carrots were short but super fat, like little round disks. I guess they just spread out instead of going down.