Early carrots require deep, sandy loams soil that will warm up quickly in the spring; it must also be well-drained; main-crop varieties can cope with heavier soils. The soil must be prepared the season before the crop is to be planted, freshly manured beds will make the roots fork instead of growing long and straight.
Add manure and compost at the rate of 4 oz. (120g) to the sq. yd. in the autumn of the previous season, dig over heavy soil and allow it to stand rough through the winter; it will then be easily forked down in the spring.
Carrots will not germinate if the soil is too cold or too wet. March is normally a good month for sowing carrots but the position should be sheltered and sunny. The alternative is to use cloches to help warm up the soil,
By positioning them over the bed where the carrots are to be sown in early March, the soil will have a chance to warm up before sowing takes place.
The cloches can then be left in position even after sowing if the weather has not improved. Do not sow all the seeds at the same time; make successional sowings with about 2 weeks between each sowing until the middle of April.
The seeds need to be sown about ½ in. (12mm) deep, if it is mixed with a little dry sand it will be easier to sow thinly. After the mix has been sown into two short rows it can then be raked lightly to cover the seed.
Carrots can be stored and used in the winter months and for those they should be sown about the middle of April at a slightly deeper depth of ¾ in. (19mm) and about 15 in (381mm) apart. The main sowing period comes in late July. Choose the quick-maturing varieties to make sure that the tender young roots are ready to pull in the autumn and early winter.
One good point about late sowing is that it tends not to be troubled by the formidable carrot fly, which is at its worst in early June.
Growing Timing To Avoid Carrot Fly
Sowing can take place as early as February/March if a fleece is being used, this will mean that the carrots can be lifted in July. Therefore the soil will be cleared before the second generation of larvae develops.
Seed can be sown in early June, therefore the carrots will be relatively young at laying time and much less attractive as the odour which attracts the fly in the first place has yet to develop. The carrots should then be lifted at the end of October/November, leaving the ground clear with nothing for any larvae to feed on.
Take great care to sow thinly, which will make it unnecessary to thin out later for this action too helps to release odour that will be an invitation to passing flies.