Native to Afghanistan, carrots are known botanically as Daucus carota sativus. The key to success in growing them is loose, deep soil: Carrots reach smooth perfection only in light soils free of stones and clods. If you have heavy clay or rocky soil, plant in raised beds or choose short-growing kinds. Carrots are a good spring crop and even better for fall; their flavor sweetens as the weather cools. You can leave roots in the ground until a hard freeze, pulling them as desired. In the Coastal and Tropical South, grow them as a winter crop.
For spring harvests, sow seeds about 6 weeks before the last frost. To extend your harvest, make two or three small, consecutive plantings 10 days apart. For a fall crop, sow in midsummer in the Upper and Middle South, in August or September in the Lower South. For winter crops in the Coastal and Tropical South, sow in November or December.
Plant the right selection for your type of soil. Long grocery-store kinds, such as 'Scarlet Nantes' or 'Envy' require loose, sandy soil at least 1 feet deep. For shallower, heavier soils that contain some clay, try blunt-nosed, half-long selections such as 'Bolero', 'Danvers Half Long', 'Nelson', 'Royal Chantenay', 'Yaya', and 'Sweet Sunshine' (a yellow carrot). For containers, try miniatures like 'Little Finger' and 'Short 'n Sweet', baby carrots like 'Baby Sweet' and 'Sweet Baby Jane', and round ones like 'Parmex' and 'Thumbelina'.
Before planting, work into the soil 12 cup of 10-10-10 fertilizer per 10 feet of row. Cover seeds with no more than 14 inches of soil. If your soil tends to crust over when dry, cover the seeds with sand, milled peat moss, or potting mix instead of soil. Seeds may take 1 to 3 weeks to germinate. Keep soil evenly moist. When seedlings are 2 inches tall, thin them to 24 inches apart. (You can steam these tiny carrots in butter or chop the entire miniature plant, tops and all, for a fresh addition to tossed salads.) Cover root tops with soil to keep them from turning green, which results in bitterness. Most types are ready to harvest 60 to 70 days from sowing.