How to grow carrots and best varieties

Whether you grow carrots in spring and summer for quick, tasty crops or in the autumn for larger roots to store over winter, they're one of the tastiest crops you can grow. 

The Which? Gardening team share their growing tips and our Best Buy varieties.

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Baby carrots for pots or in the ground

Maincrop carrots

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Do carrots have to be orange?

Carrots weren’t always orange. Most wild carrots are white or purple, while yellow carrots are thought to have derived from purple ones, thanks to a gene mutation.

Dutch growers bred orange carrots from yellow varieties in honour of William I of the Netherlands, Prince of Orange. Breeders now use wild carrots as a way of increasing the nutritional value of new varieties.

We tested eight non-orange carrots and, while we really liked the look of some of them, we were disappointed by the weight of the crop and the taste. We found most of the purple carrots tasted bitter and astringent, while some of the white and yellow ones were just a little flavourless. Many were also woody and tough .Only ‘Atomic Red’ had an outstanding taste, but it yielded a tiny crop

Do carrot-fly resistant varieties taste good?

We found one of the best ways to beat carrot fly is to grow a resistant variety. In our trial, we wanted to directly compare the taste of three carrot fly-resistant and non-resistant varieties to find out which is best to grow. ‘Flyaway’ This is quite sweet and was good eaten raw, but its flavour isn’t as strong as some of our Best Buys. 'Resistafly’ We think it’s best eaten raw when it’s sweet and tender. It loses some flavour when it’s cooked. ‘Maestro’ Opinion on taste was divided. Some of our tasters liked it and thought it was quite sweet, while others found it bland. It’s best eaten as a young carrot.

When to sow

Sow in May for crops that will stay in the ground into winter. Earlier crops can be sown from April, and you can sow until August if autumn is mild. 

Sow a few carrots every few weeks for a succession of crops. Carrots like sandy soil and don’t grow well in clay soils, or in very stony ground. In this case, grow in pots or raised beds

Carrots fork if there is too much nitrogen in the soil. Add manure to the bed the previous autumn and let it break down. A slow-acting, phosphorus-rich organic feed, such as bonemeal, is better for carrots than a nitrogen-heavy, controlled-release fertiliser.

Dig over your plot well, making sure the ground is crumbly enough for roots to push down into and the surface is fine enough to cover the seeds evenly.

Create a drill around 1cm deep and sow seed thinly, then pull the soil back over the seed and water in gently. When the seeds have germinated, thin to around 5-7.5cm between carrots.

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Caring for your plants

Cover your seeds with insect-proof mesh to protect from carrot fly. Carrots shouldn’t need much watering. If the foliage starts to wilt, give them a good soak. Weed between the rows regularly, using a hoe or a hand fork. Carrots don’t grow well if they have to compete with weeds.

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How and when to harvest

Baby carrots can be harvested from around nine weeks after sowing, but maincrop carrots will need at least 12 weeks to mature. Short carrots, such as chantenay types, can behand-pulled. Longer carrots will need to be gently lifted using a digging fork.

You can leave carrots in the ground until January. Or, store them in a cold, dry, dark space, such as a garage or shed. 

Growing in a pot

You don’t need a deep container to grow baby carrots. Use a 10L or 15L pot, or a windowsill trough and a Best Buy compost for patio pots. If you want to leave your carrots in their pots to mature into maincrop carrots, you will need to add a little bonemeal. This is better than using a controlled-release or liquid feed as these are both very rich in nitrogen, which makes carrots fork. However, if you want to grow baby carrots, there’s no need to feed them: there should be enough fertiliser in the compost to last around six weeks.

You can sow carrots in pots from around April. It’s a good idea to sow a pot every few weeks for a steady supply of baby carrots.

Sow thinly, leaving around 2.5cm between seeds, then cover with 1cm of compost. 

When the seeds have germinated, thin to around 5cm between carrots.  

Carrots in pots should be regularly watered to make sure the compost doesn’t dry out, but avoid keeping them too damp. Weed between the carrots regularly by hand to make sure the carrots don’t have to compete for water and nutrients. 

Baby carrots are ready after around six weeks. The ‘shoulders’ of the carrot should be around 2cm wide when they’re ready to harvest.

Empty out the whole pot, or if you only want a few carrots, pull out a good clump and firm back the compost to let the rest of the pot grow on undisturbed. You may need to add a little more compost to the pot to fill the gap.

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Common growing problems

Carrot fly

Carrot fly can be a real problem. They lay their eggs on carrot tops and the developing larvae eat their way through the root, leaving black tunnels that can make the whole carrot inedible. Affected carrot plants look stunted and 'rusty'. The leaves are small and develop a reddish tinge, before turning yellow and dying.

We found the best way to avoid this is to either cover the crop with insect-proof netting, pegged down around the edges, or grow a carrot fly-resistant variety. Thin seedlings, water and weed on a warm, dry afternoon, when carrot flies are less likely to be flying, and cover with mesh as soon as you have finished.

There are two attacks a year. Where last year's crops were infested, the flies overwinter as pupae. The pupae are tiny, yellowish cylinders with dark ends, and their small size and colour make them hard to spot.

The first fly generation emerges from May. They lay eggs near susceptible plants, which hatch into white maggots. These tunnel into the roots and feed there in mid-summer. They in turn pupate and hatch into the second generation. The second generation then lays their eggs. The larvae tunnel into the roots in the autumn, and sometimes continue to feed all winter. They will all have pupated by late spring, and will be ready to hatch.

Slugs

If slugs are nibbling your seedlings and plants, sprinkle a few organic slug pellets containing ferric phosphate pellets around the crop.

Read more about slugs

Splitting

Sometimes carrot roots split, generally lengthwise – and there may be several of these longitudinal splits – often penetrating to the core, on any one root. Secondary rot-causing organisms may enter the damaged flesh and cause extensive discolouration and deterioration. If lifted promptly, the split carrot may appear perfectly sound.

You can use split carrots for cooking. As soon as you pull any split carrots, start to water regularly to prevent others from splitting.

This problem occurs almost exclusively as a result of erratic moisture levels in the soil, so before sowing, improve the soil texture by incorporating plenty of bulky organic matter. Then when the crop is growing, water regularly so that the soil is kept just moist at all times.

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How we test carrots

Varieties for pots

We chose 25 varieties that we thought would do well as baby carrots and grew them in 15L pots filled with a Best Buy compost for patio pots in our trial gardens in Cambridgeshire. Each pot was covered with a fine mesh to keep out carrot fly. We know  that some varieties take longer to grow to baby size and the flavour can develop as they grow, so we grew four pots of each variety, harvesting the first pot after six weeks, then one pot per week for the next three weeks to see how long they took to reach the perfect size and if more mature carrots tasted better. We weighed and counted the carrots from each pot, grading them to see how many were baby-sized or were too large or too small to fit the bill. We tasted every harvest.

Maincrops

We chose 25 varieties of carrots, selecting old favourites and new varieties we haven’t tested before. In mid-May, we rotavated the ground at our test site, levelled it and added bonemeal. We sowed two 2m-long rows of each variety, and once thes eed had germinated, we thinned them to 5cm between carrots. To avoid our crops being attacked by carrot-root fly, we covered them with fine insect-proof mesh. We harvested three-quarters of our carrots after 12 weeks, in mid-September, and left the rest in the ground, pulling up the remaining carrots in early December and also in mid-January. We weighed, measured and graded the carrots, looking for any with defects, including splits, fangs, green tops, and small or mis-shapen carrots. We tasted them, giving a score for how easy they were to prepare and how tasty they were when eaten raw or cooked