I harvested the last of my carrots this January, several of them were large, two or more inches across and reasonably long. I have had carrots that reached from my elbow to nearly my knuckles, that's more than a foot long. But it was not always like this. There were failures. My first attempt, when I grew directcly in the ground, was a disaster, as none grew, and then I found that our plot is bad for carrots, so no one did well. I don't know why. So I tried containers, and it worked, but the carrots were small and stubby. I then found out that I had been watering from the top, and if you do this the carrots never grow long. This is because the root extends to find water, and if it has to go deep it grows long, and then begins to fatten out with nutrients. If all the water comes from the top the plant is too lazy tog row long.
I settled on containers. First I used cut down plastic drain pipes, and these were great. I got my longest ever carrots from them, but they were vulnerable. When we had very heavy rains, the water washed the carrot seedlings down and I got nothing. I finally settled on raised beds, which worked well for both carrots and their kinsfolk in the Umbelliferacea, parsnips.
The key with carrots is that they like a soil which is deep, light and free of obstacles. If the soil is deep the carrot will have an unimpeded search downwards for water and nutrients, but if there are stones to obstruct its path it begins to fork and is harder to peel. Our carrot originated in Afghanistan, so it likes a bit of sand in the soil, so I always like to mix sand and compost together to grow them.The sand lighten the soil and the compost provides the richness that fattens the carrot.
Ideally, if you can get the water in from the base of the raised bed, the carrot will lengthen well. But you will need to thin the carrot seedlings, as they grow into each other and produce some very strange shapes. Actually shape does not matter, and it is only the sort of finicky people who only use supermarkets who bother about it.
Note also that carrots can be of different colours. The reason that we have orange carrots is that we took our carrot varieties form the Netherlands, who grew orange in favour of their national colour, which derives from the house or Orange, their royal family, so people think that carrots have to be orange. I have grown yellow and purple carrots, and the yellow ones are tasty. You can get black, green, yellow and white ones. You often see these on display at flower shows. All are equally good.
Parsnips are more or less the same as carrots where growing is concerned, except that they are hardier and easier to grow. They have large leaves, and the plant can produce some very large roots that are fat and deep. We have a soup maker and we mix parsnips into the blend. We are quite happy with what is produced. The carrots are used for the main course.
Both carrots and parsnips should be kept weed free to ensure that the soil's nutrients go to them rather than the weeds.It is better that the soil be cleared of weeds, particularly perennial ones before you plant, and never let any weed become large, as carrot seedlings are very vulnerable and can be shaded out.
But you need to protect carrots from the carrot root fly. This little beast likes to lay its eggs near carrot roots, and then the larvae eat their way into the root. There are two defences. The first is to use the fact that the fly cannot fly more than eighteen inches [forty five centimetres] above ground, so netting stretching higher than this defeats them. Secondly, palnt marigolds near the carrots. For some reason the fly hates the smell of marigolds and it is deterred by it.
Note that the carrot tops, the greens, are just as edible as the carrots are and can be used in salads.
Use a fork to take the carrots out. Be gentle with them, as they can snap, so lever up the area round the carrot and shake the fork to release it from the soil encrusting it. Spades are more likely to cut the carrits than forks are.