How ongong a carrot’s root is depends partly on genetics (some miniature carrots never make long roots), but is also influenced by the environment. Deep, loose soil without stones, in particular, will give long, straight roots. Hard clay soil, or soil filled with stones or rocks, will give shorter carrots that are often forked or split.
The longest of long carrots are grown in Great Britain where longest carrot competitions are commonly held in agriculture fairs. The results can be surprising: the world-record holder, grown by Joe Atherton in 2016, measured an astounding 20 feet 5.86 inches (6.245 m)! Atherton’s secret is to grow his carrots in 21-foot (6,4 m) plastic tubes standing upright, filling them with ordinary commercial potting soil, which is free of both stones and clay. So if the idea of smashing the world record stirs you seems like a fun challenge, you now know what to do!
In The Home Vegetable Bed
If the soil in your vegetable garden is not 21 feet deep, you can still grow carrots of a quite acceptable length – say about 8 to 12 inches (20-30 cm) long – as long your soil is loose, free of stones and at least 40 to 45 cm deep. That’s why most home gardeners find they get the best carrots in raised beds filled with quality soil brought in from a reliable source rather than in regular beds whose soil has simply been improved with compost over the years. The latter usually have too much clay and too many stones for perfect carrot growth, although if your garden soil is naturally sandy, you’ll find that simply enriching it with compost does indeed give great results.
If your soil is really thin or almost pure clay, though, try round rounds, such as ‘Atlas’. They give excellent results even when soil conditions are not optimal. Or just grow standard carrots and learn to live with their shortened, forking roots. They may be harder to peel, but they’ll still taste just as good.
Carrots can be sown as soon as the soil can be worked, which would in late April or sometime in May in most climates.