There are many varieties to choose from and all are very good, but some are better than others for specific purposes
It has already been mentioned that on shallow or stony soils, round or short-rooted varieties are best, unless you decide to build a raised bed on top to negate any problems. In the catalogues you will also too carrot fly resistant ones, those recommended for exhibition and others of different colours, from white to purple.
BEST FOR VERY SHALLOW/ STONY SOILS
‘ATLAS’: ‘A Paris Market’ type, with round roots and a crunchy texture. (Marshalls)
‘PARIS MARKET: A heritage variety with spherical roots that’s ideal for growing in containers or shallow soils. (Widely available)
‘EARLY MARKET’: Stump-rooted type good for early or late sowings. (Kings)
BEST FOR EARLY SOWING
‘EARLY NANTES’: Great for sowings and container growing (Widely available)
‘AMSTERDAM FORCING 3’: A good one for starting under cloches in early spring. Best eaten young (Widely available)
‘NORWICH’: A Nantes type with long, uniform roots, (simplyseed)
BEST FOR STORING
‘ESKIMO’: Great cold tolerance makes this a good maincrop carrot for cold regions (Suttons)
‘AUTUMN KING’: A maincrop carrot. Very hardy so can be left in the ground over winter in most soils. (Widely available).
‘ST VALERY’: Uniform maincrop type with good colour and flavour. Good for the show bench.
‘CHANTENAY RED CORED’: Time-honoured stump-rooted maincrop, great for shallower soils (Widely available).
If you intend to lift your crop for winter use, this is best done once growth slows end the foliage starts to yellow in late summer/early autumn. Lift crop, wash the roots to remove most of the soil and allow to dry before storing in trays of dry sand, peat or in hessian sacks. In all cases keep the roots cool, dark and out of the roach of vermin.
Wild carrots from which our modem varieties are bred were white-rooted and you may occasionally find one or two of these among your crop. Our familiar orange carrots are not thought to have come about until the 1700s in Holland and were derived from yellow forms.
Seed packets often advise sowing from February onwards, but this is a risk unless you garden on sandy, free-draining soil. On heavier or water-logged soils it is better to wait another month or two to give the crop the best chance of success.
Do not be tempted to sow early crops until the soil has warmed sufficiently. Wait if it is below 7C, when checked with a soil thermometer, or if conditions are very wet.
Avoid towing on windy days. Water the drill prior to positioning the tape; the paper will absorb the water and stick to the soil, helping to prevent it from blowing away before you can cover it up. Water regularly to help the paper to biodegrade and to allow the seedlings to break through.
You can look here interesting tips about growing carrots too.