Kuroda
Carrot in the US

Carrots are best sown direct into the soil once the ground warms up, usually after your last frost date. Check your USDA zone; for instance, folks in zone 3 might start in May, while those in zone 9 can get going as early as January. Sow seeds thinly about a quarter-inch (6mm) deep in drills, leaving about 12 inches (30cm) between rows. You can sow a small batch every few weeks from spring through late summer for a continuous harvest. Just remember, these timings are a guide, so adjust for your local climate.

Once your carrot seedlings are up and showing a couple of true leaves, you'll need to thin them out. This is important, as overcrowded carrots won't develop well, you know what I mean. Aim for about 2-4 inches (5-10cm) between each plant, depending on the variety. We're not usually faffing about with plug plants for carrots; they much prefer to grow where they're sown.