Grow Your Own Carrots

Lesson 3: Thinning Carrot Seedlings

Bruising Encounter
Carrot seedlings normally start to appear 2-3 weeks after sowing. Once they're big enough to handle – around 2.5cm tall – weaker seedlings should be removed. With most vegetables, this thinning-out process merely means making sure the strongest plants are left at the correct distance from each other. When you're thinning out carrots, however, you need to ensure that you keep any bruising of the seedlings to a minimum. This is because the carrot fly, a major pest, is attracted to the smell of the bruised foliage. Handle the thinnings as little as possible. Don't leave them lying around the vegetable plot – burn or bury them straight away.

Evening Shift
Many gardeners recommend that you thin carrots in the evening to reduce the likelihood of a carrot fly attack. It's also believed that firming and watering the remaining seedlings immediately after thinning helps to keep this pest at bay. Whatever steps you've taken to reduce the carrot fly threat, aim to leave 5-8cm between your remaining seedlings. Hoe between rows of young carrots to keep weeds down but the plants' own foliage should discourage weeds as the crop matures. Water regularly.

Fly Flighters
Another defence against carrot fly is the use of fine netting. Carrot flies are around 1cm long, so they won't be able to penetrate the finer netting available from garden centres. What you're trying to do is to stop the carrot fly laying its eggs in the soil around the base of the seedling: the resultant larvae eat into the roots. Lay the netting over a simple, low frame to protect seedlings. When the carrots are older, trying surrounding them with a vertical fence of fine netting, at least 70cm high. A mulch of grass cuttings has also been known to deter carrot flies – the mulch makes it difficult for the fly to get to the soil to lay its eggs.

Pic: GAP Photos/Claire Davies