Carrots grow best in light, stone free, well drained, humus rich fertile soil.
Sandy peaty soils provide the best conditions for roots to penetrate deeply and to swell.
The pH value should 6.5 to 7.5 for best results.
If you have heavy soil, dig in plenty of manure, leaf mould and or home made compost several months before planting.
Never work fresh manure into the soil as this encourages sappy growth and forking of the roots.
Carrots appreciate a sheltered sunny position.
To avoid the build up of diseases grow them in a different bed each year.
If practical work to a three year rotation cycle or greater.
Do not be tempted to sow too soon, soil temperature can be critical, for instance at temperatures below 5 ºC, they will struggle to germinate.
Seeds sown as slightly higher temperatures can take up to 35 days to germinate, whereas if you wait until the soil is 10 ºC + (50°F+) germination should occur within ten days.
Root growth is fastest at a temperature between 15 ºC and 18 ºC.(60°-65°F)
As a guide start sowing about two weeks before the last expected frost in your area, then make successive sowings every three weeks there after, but avoid sowing during the hottest part of summer.
There are three main groups of carrots are: short / stump rooted, intermediate-rooted and long-rooted.
Short / stump rooted varieties are best used for an early or forced crop, Intermediate varieties for main crop, and Long rooted varieties for exhibition purposes.
Since one can generally offer some type of protection when growing in this manner, preparations for exhibition carrots can take place a little sooner than carrots that are sown directly into the ground.
circa Week 16-18:
Select any type of container you have at your disposal and fill it with river / sharp sand.
Deep barrels for exhibition varieties
Bath for intermediate / stump rooted
Shallow barrels for intermediate / stump rooted
Once filled, bore tapered holes in the sand with a crowbar (or similar) resulting in a 100mm (4") hole at its top.
Space the holes 200-300mm (8"-12") apart.
Fill the holes with sieved potting compost, pressing it down firmly with a stick.
Thoroughly soak the container with water.
There are growers who advocate that if growing outdoors no further watering should be required other than that that falls as rain, meaning the carrots will have to grow in length to seek moisture which is a valid point.
Then there are others who say soak the container once a week, particularly during during very hot dry weather.
Meaning it is up to the individual grower to choose the method he/she finds best, personally I tend to let common sense prevail and water to suit the prevailing weather conditions that is:
I do not water in wet seasons, and water more regularly, but not necessarily weekly when the weather is changeable or hot and dry.
The reverse is true if the containers are undercover where in such cases one should never allow the containers to dry out.
Sow a pinch of seed in each hole.
Cover the container with a sheet of glass until germination.
When the seedlings appear remove the weaker ones, leaving the strongest one to grow on.
If the containers are in a greenhouse or tunnel these tasks can be completed up to a month earlier.
Rake in a low nitrogen fertiliser into the bed at the rate of 100gms (4oz) per sq metre.
Excess Nitrogen causes branching and hairy, fibrous roots.
If soil temperatures are sufficiently high, sow seeds very thinly in 25mm (1") deep drills 300mm (12") apart.
Soak the drill prior to sowing the seeds and this should ensure that there is sufficient moisture in the soil to last until after germination.
Seeds can be mixed with little silver sand to make sowing a little easier.
Do this by adding ½ a teaspoonful of silver sand into the seed packet and shaking it to mix the seed and sand together.
Germination will take around 10 - 12 days.
Earlier sowings can be made if ground conditions allow, providing cloches are placed over the rows.
Successional sowings of early varieties at fortnightly intervals will prolong the season.
Prior to sowing in manured or stony ground insert the blade of a spade into the bed and push it backwards and forwards to form a Vee shaped trench.
Trickle in a proprietary potting compost into the trench and sow the seed as previously described.
This method is particularly beneficial in dry seasons, because the manure retains sufficient moisture in the ground between rain showers to keep the carrots going.
This method also reduces the chances of stunted or forked growth.
Thin crowded seedlings, when large enough to handle, to 25mm (1") apart, then thin out again a couple of weeks later to 50mm (2") apart.
To reduce the risk of attracting egg-laying carrot flies when thinning, do the job at dusk.
After thinning, water along rows to settle soil around remaining seedlings.
Cover the bed with fleece, but before covering, rake in a high potash fertiliser at 80gms (3oz) per square metre.
Prepare the soil for the following season by digging it deeply and leave it rough through the winter for frost to break it down
Some would say don't dig in manure at this stage as this may cause the roots to fork, and where possible, grow carrots on a plot that was well manured the previous season.
This is a valid point, but it can also be said, that well rotted compost added at this time will have around eight months to rot down even more by the time the next crop is sown.
With this in mind, and before deciding which way to approach this decision one should consider the quality of their soil.
For example: In the case of light soils one would be adding humus to it, and on heavy soils one would be lightening it, the choice is yours!