There are dozens of different carrot varieties, usually described as early or maincrop varieties, but also described as either short-root or long-root varieties. These names indicate when they crop and also give you an idea of the type of soil that they are suitable for. Carrots grow best in light, sandy soil. If your soil is heavy clay, stony, chalky or doesn’t drain particularly well, you should concentrate on the maincrop, short-root types as they will cope better with these conditions.
Early carrot varieties take around 12 weeks to mature and maincrop carrot varieties are ready in around 16 weeks. Maincrops take up the most space in the garden, but they tend to be the best varieties to grow if you want some for storage. You can use the same techniques for parsnips, but they need to be in the ground for longer.