IF YOU live in an area where carrot fly is a problem, as I do, you’ll find raising carrots in containers a lot easier than growing them in the open soil. Carrot flies lay eggs in the soil near carrot seedings, and the maggots that hatch out of them burrow into the carrot root, making it inedible. It is possible to minimise the problem with barriers of fleece or very fine mesh, but the slightest opening through May to late August can let the flies in.
Growing carrots in pots means you can protect the crop much more easily. Carrot flies buzz around just a couple of feet above the ground, so moving pots up high is a simple way of keeping them safe. it also means you can get seeds sown really early – these were sown in mid January, very thinly. I try to space seeds about an inch apart (2.5cm) on pre-watered multipurpose compost, but they still need thinning because I never get the spacing quite right!
The sown seeds are covered lightly with vermiculite and the 5 litre pot squeezed into a cheap 1 x seed tray sized heated propagator (which I bought from B&Q for under a tenner four years ago, and it’s still going strong).
Good germination usually results, as you can see. The trick is to always buy fresh seeds – carrot seed seems to deteriorate quite quickly if kept for more than a couple of years.

Thinning is a boring job that requires nimble fingers, but it is essential if you want a pot of carrots that all grow to a decent size. Fail to thin and you might get one or two well-sized roots, but the rest are likely to be very weedy.
To thin the seedlings, identify the ones that need to come out so that you’re left with sturdy seedlings spaced 1-1/2in (2.5- 3.5cm) apart across the compost.

Grasp the offending seedling firmly between thumb and forefinger, and lift steadily but gently. it’s sometimes necessary to hold down the compost around adjoining seedlings to prevent them being lifted too. Remember, once they’re out, they’re out.

There we are – this one lifted out nice and cleanly. It helps to let the compost dry out a little which allows the roots to lift. Wet compost seems to stick around them.

Keep going until you’re happy you’ve removed all seedlings that are closer than 1in (2.5cm) to each other. It can be a bit worrying to see so many healthy seedlings bite the dust – but you’ll see it’s worth it as the rest mature.

The final job is to carefully water-in the seedlings remaining in the pot. Avoid their foliage and water directly onto the compost – this small house plant watering can makes it much easier.
Pop the pot back in a bright spot (high up to avoid carrot fly), keep the compost moist and start to feed once a fortnight when the foliage gets about six inches tall.