onion cultivation

Onion cultivation adapts to all climates and needs little fertilization.


A distinction is made between white onions, intended for fresh consumption in the spring (even if they can be stored), and colored onions, for storage.

white onions

Sow at the nursery – at a rate of 5 g per m² – in the second half of August or early September.

When the plants reach 15cm (between mid-October and mid-November), plant them in a line spaced between 15/20cm to 8cm on the line. Bury the plants at 2-3 cm by firmly bordering (wrapping around the plant).

You can also sow directly in rows with a spacing of 15/20 cm. You will thin out to 5-7 cm (removed seedlings can be transplanted elsewhere)).

Onion seedlings, both in the nursery and directly in place, are quite tricky.

The easiest and safest method is to plant bulbils (see below).

For white onions, bulbils are planted either in fall or late winter/early spring.

colored onions

You have 2 options:


Sow from late February to early April in rows 20-25 cm apart.

Thin to 7-8 cm (you can transplant the removed plants elsewhere, or use them to fill in any gaps in the crop line).

Onions take a long time to rise. I recommend that you hoe quickly (once you emerge).

Planting bulbils is easier…

Bulbil Plantations

From the first half of March, plant 12 cm apart in rows 20 cm apart.

Proceed by pushing the bulbs to a maximum depth of 2-3 cm.

Keep in mind that onions from bulbils are generally larger than those from seed, but they have a shorter shelf life.

Recommended associations with an onion crop

Alternate rows of onions with rows of carrots (same repellent as leeks).

The onion also appreciates the proximity of lettuce, beets, parsnips or even radishes, but fears that of peas or beans.

Fertilizing an onion crop

As a general rule, onion cultivation does not require additional fertilization.

However, if the soil does not contain potassium (essential for bulb growth), or if this element is poorly released, add comfrey, beetroot vinasse or patenkali (fast effect) during cultivation.

Take care of onion cultivation

Onion crops should be planed and weeded regularly.

A light mulch during cultivation can also be considered.

Watering is normally not necessary… except during heat wave and prolonged drought (but water very moderately).

Crop protections

The onion is not very susceptible to attacks. However, onion maggot or onion rot are sometimes rampant.

onion fly

The leaves are gnawed and withered… This is probably damage caused by the larvae of the onion fly.

The yellow-gray fly resembles the housefly and measures about 7 mm. The larva is white and shiny and measures 5 to 8 mm.

Only the first generation (flights from mid-April to the end of May) can cause significant damage, namely the destruction of the foliage and thus the cessation of plant growth.

To prevent this, a few preventive rules are generally sufficient:

  • Practice crop rotation
  • Do not use manure or nettle fertilizer for your onion cultivation
  • Sow or plant late (drought destroys eggs)
  • do not water
  • Between your onion crops with carrots
  • Cover with an insect net during the flight period

In case of an attack during the flying period (twice a week) spray a decoction of tansy.

Uproot and burn affected plants.

onion rot

The fungus (botrytis) responsible for onion rot enters the bulb in late summer, but only appears during storage.

Preventive action:

  • Do not add fertilizer for your onion plantations
  • Treat the soil preventively with a decoction of undiluted horsetail
  • Dry the bulbs completely after harvest

onion harvest

White onions are harvested fresh, in the spring, as and when needed.

Colored onions are harvested in dry weather, when the leaves are 2/3 yellowed (July-August).

Keep the leaf and let the onions dry in the sun for a few days before placing them in a cool, ventilated place for winter storage.