I bought carrot seeds last year that I never got around to planting so I planted them in May of this year. This particular carrot is called "Carrot Tonda di Parigi." I bought the seed packet online from Baker Creek Heirloom Seed Company. This is a 19th-century Parisian heirloom carrot that only grows to about 2". I harvested these a little early because I couldn't stand the suspense. They still tasted fantastic. They were very sweet and nothing like the bland, watery carrots that I always seem to get from the grocery store.
So this type of carrot seed can be planted in 2-3 week intervals all the way up to the first heavy frost. And because they are short and stubby, a deep pot is not really required. It takes about 60 days for the carrot to reach maturity.