Succeeding in leek cultivation

Location and soil

Leeks thrive in full sun, in deep, rich soil. An application of compost or manure is necessary, ideally at a rate of 3 to 4 kg per m², preferably a few months before planting, as leeks are sensitive to fresh amendments.

In the vegetable garden, leeks pair very well with carrots, as well as with celery, Swiss chard, and strawberries. However, avoid planting them near garlic, onions, shallots, and beetroot.

The choice of variety

Each variety of leek corresponds to an ideal sowing period, which can vary in length: this information is found on the seed packet, and it is important to refer to it. Generally, for a harvest:

• in summer, sow from early March to mid-May,
  e.g. ‘Gros long d’été’, ‘Jaune gros du Poitou’, ‘Géant précoce’
• in autumn, sow from mid-March to the end of April,
  e.g. ‘Monstrueux d’Elbeuf’, ‘Electra’, ‘de Carentan’
• in winter, sow from April to mid-May,
  e.g. Bleu de Solaise, ‘Vernor’, ‘de Saint-Victor’

Easy sowing and planting

Sowing is carried out in open ground nurseries or in sufficiently deep trays, such as fish boxes, at a minimum temperature of 13 °C. Once the young plants have reached the diameter of a pencil, dressing and planting in their final position is carried out, spacing the young plants 15 to 20 cm apart in the rank.

Slow growth and hilling up recommended

The growth of leeks is quite slow. To obtain beautiful “whites”, one can either:

• plant in deep furrows of 10 to 15 cm that will be filled in as the leek grows,
• carry out earthing up when the young plants start to develop.

Regular maintenance involves performing regular hoeing and weeding. Watering should be regular.

Pests and potential diseases

Leek moth (or “worm”) and leaf miner are the main pests. The caterpillars or larvae burrow into the leaves and then settle in the bole.

Among all the preventive measures, the installation of an insect net is the most effective. However, it can be accompanied or replaced, if you believe you are not in a high-risk area, by:

• association with carrot,
• the establishment of a mulch made from repellent plant waste (lavender, tansy).

The most common disease is Rust. It is a fungal disease that appears in late summer as small orange spots on the foliage. This condition is treated with sprays of horsetail decoction or Bordeaux mixture. Some varieties such as ‘Below Zero F1’ or ‘Oarsman F1’ are less sensitive to it.

The harvest

Harvesting takes place between 5 and 8 months after sowing and is done as needed. To do this, gently pull on the leek. In heavy soil, use a fork to lift it a few centimetres away from the leek to raise it without damaging the bole.