Lars Lund

27 Jul 2023 11:41

Success with carrots

By Lars Lund


There's nothing quite like pulling up fresh and juicy carrots. However, that joy quickly fades when you spot that your carrots were attacked by larvae. That's the work of the carrot fly, which lays its eggs between the roots. The visible result are larvae eating their way through the carrots making them inedible, also because of the bitter flavour the carrots develop.

This problem is particularly significant in organic horticulture, where people have been trying to combat these destructive flies for several years.

Sowing Time

The carrot fly has two generations, and sometimes even three. The first generation of flies appears at the end of May or the beginning of June, while the second generation emerges in July and continues until the middle of September. The damage caused by the first generation isn't severe, but it does negatively affect root development, causing some crops to wither. The second generation inflicts much worse damage, creating small tunnels in the roots and affecting the taste of the affected areas.


Quick Development

The carrot fly lays its eggs close to the soil surface and near the plant itself. The eggs hatch quickly, so within a week or two, there are larvae that immediately start nibbling. They grow larger and fatter, and when they are big enough, they go deeper into the soil to pupate. By late July, they are ready to fly and lay eggs. It's not only the carrots that are affected; it can also affect other umbelliferous plants such as parsley, parsnip, celery, and dill. With the first attack, you will see some of your parsley or carrots wilt.

Combatting the Carrot Fly

To confuse the carrot fly, you can try using smells that are different from the smell of umbellifer flowers. Onion oil has shown promising results but be aware that it has a strong smell that can be difficult to remove from clothes. Another method is to place onions between the carrot and parsley, which confuses the carrot fly to some extent. However, the most effective approach is using an insect net.

Four Tips to Protect Your Carrots from Larvae

  1. Sow summer carrots in early April so that they have time to develop before the first generation of flies causes damage.
  2. Sow winter carrots in early June and cover them with an insect net by the end of June. Keep the net in place until harvest, ideally until early September, as one generation of carrot flies replaces the other. Additionally, you can deter the carrot fly by setting up a net fence. The net should be around 60 cm high.
  3. Regardless of whether you choose summer or winter carrots, cover the neck of the roots with grass cuttings or soil.
  4. Remember to rotate your crops. Wait for at least four years before sowing umbelliferous plants in the same soil again, as there may be fly larvae present in the soil.


Pre-Germinating Carrots

Although it's not necessary, you can pre-germinate carrot seeds. Pour the seeds into a cup or plate and lightly cover them with water. Let the seeds soak overnight, then drain the water using a coffee filter, for example. Place the filter on a green foam moss in a bowl of water to keep it moist. This arrangement should be kept in the refrigerator. After around fourteen days, the seeds will crack, indicating that they are ready to be planted in the garden.

Sowing in Milk Cartons

Another method is to sow carrot seeds in milk cartons, either indoors or in your greenhouse. When it's time to plant them out, remove the bottom of the milk carton and place the seedlings in a hole in the size of the carrots. If you sow them in small pots and later transplant them, the resulting carrots may be deformed, or they may not survive.

Easier Outdoor Sowing

To make outdoor sowing easier, prepare a kind of porridge by boiling a litre of water and adding four to five tablespoons of cornflour. Stir vigorously until the mixture thickens and allow it to cool down before placing the seeds in it. Ensure the temperature stays below 35 °C. Fill a plastic bag with the mixture of seeds and porridge, then cut a corner of the bag and squeeze the mixture into the seed furrow. The seed furrow should be around 3 cm deep. Approx. 10 days later, the tops of the carrots will emerge from the soil, making it easier to distinguish between desired plants and those that need to be removed. Alternatively, you can purchase seed tapes that are pre-spaced, but keep in mind that not all seeds sprout.

Sowing and thinning out

If you take precautions against the carrot fly, you can sow when the soil temperature reaches 4 °C, but it's better to wait until around April when it's a little warmer. The soil should be porous and free of rocks, as rocks and hard soil can cause the carrots to separate. Use a stick or a dibble to create a 1-2 cm deep furrow and cover it with soil. As the plants grow, thin them out so that there is approx. 5 cm of space between each carrot.

Later, when the carrots have grown larger, remove every other carrot. The smaller carrots that are removed can still be consumed and are quite tasty. Keep the plants well-watered and cover them with grass cuttings to retain moisture. If the soil dries out completely and then all over sudden gets a lot of water, the carrots may crack.



The selection of carrot varieties is almost endless. I recommend exploring options online or buying seeds from a known variety that you enjoy. Here are some examples:

  • Nantes: A popular variety that produces long, slim carrots.
  • Nantes 2: This early and fast-growing sort can be harvested in July but is not suitable for storage. Organic seeds are available.
  • Jeanette White Satin and Yellowstone: These summer carrots offer different colors if you're looking for something unique.
  • Paris Market: These carrots resemble round radishes in shape.
  • Berlikumer 2-Buzzy: A winter carrot suitable for storage. Organic options are available.
  • Flaskkese 2 - Buzzy: Another storage carrot variety.
  • Autumn King2 or Flakke2: Thicker varieties suitable for storage. Organic options are available.
  • Chanteney Red Cored 3: A thick variety with a great taste.

Remember that winter carrots can be stored if protected from frost.

Winter carrots can be stored if protected from frost. One method is to create a warm bed for them by digging a hole in the ground, covering it with leaves and spruce or pine branches. This arrangement prevents frost from reaching the carrots. Alternatively, you can also use for example garden fleece other materials instead of leaves. Another option is to place the carrots in a box, cover them with moss to retain moisture, and then insulate the box with an isolating material. By following these steps, you can successfully store your winter carrots.

If you want to learn more about getting early vegetables by germinating, you can read this related article. 


Om Lars Lund

Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.  

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