If the root meets an obstacle in the early stages of growth, it will branch or simply stop growing. Carrots prefer full sun but will tolerate partial shade, especially if the weather is very warm. Carrots produce best in a raised bed . Till the soil to a depth of at least 8 inches, adding plenty of compost or well-rotted manure. Excess nitrogen causes branching and hairy, fibrous roots.
Potassium promotes solid, sweet carrots.
Wood ashes contain highly soluble potassium, which reaches the plants quickly. As you prepare the bed, work wood ashes into the top 4 inches of soil, where feeder roots thrive. Add lime if the soil tends to be acid. Planting Carrots are cool-weather vegetables, so start sowing about two weeks before the last expected frost in your area. Make successive plantings every three weeks until but avoid the hottest part of the summer.