How to Grow Carrots: Carrots are a cool-weather vegetable. Sow carrot seed in the garden 2 to 3 weeks before the last frost in spring or about 12 weeks before the date of the average first frost in autumn.
Gardeners' Gems: Designer Crops That Will Wow The Neighbors
Parisian Carrots (55 days)...A great little round carrot that is a nineteenth-century French heirloom. It "excels in clay or rocky soil where other carrots have problems developing properly". They say it works great for containers.