Onion Cultivation

The onion cultivation adapts to all climates and needs little fertilization. It has its place in your natural vegetable garden.


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 in the nursery – at a dose of 5 g per m² – in the second half of August or the beginning of September.

When the plants are 15 cm high (between mid-October and mid-November), plant them in rows spaced 15/20 cm apart to 8 cm in the row. Bury the plants at 2-3 cm by firmly bordering (pack around the plant).

You can also sow directly in rows at a distance of 15/20 cm. You thin out to 5-7 cm (suppressed plants can be transplanted elsewhere).

Onion seedlings, whether in the nursery or directly in place, are quite a pain.

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

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

colored onions

There are 2 options for you:


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

Thin out to 7-8 cm (the removed plants can be transplanted elsewhere or used to fill gaps in the crop line).

Onions take a long time to rise. I recommend hoeing fast (as soon as you emerge).

Planting bulbs is easier…

Bulbil plantations

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

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

Note that onions from bulbils are generally larger than those from seed, but they keep less well.

Recommended associations with the cultivation of onions

Alternate rows of onions with rows of carrots (same repellent effect as leeks against the carrot fly).

The onion also appreciates the proximity of lettuce, beets, parsnips or even radishes, but fears that of peas (which is not apparent with a little experience…) or beans.

Fertilizing an onion crop

As a rule, no additional fertilizer is required for the cultivation of onions.

However, if the soil lacks potassium (essential for bulb growth), or if this element is poorly released, add comfrey, beet vinasse or patenkali (quick action) during cultivation.

Onion Cultivation Care

Hoe and weed your onion crops regularly.

A light mulch during cultivation can also be considered.

Normally, watering is not necessary… except during a heat wave and prolonged drought (but watering should then be very moderate).

Crop protections

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

onion fly

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

The yellow-grey fly resembles the housefly and is about 7 mm in size. The larva is white and shiny and 5 to 8 mm in size.

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 stopping the growth of the plants.

But a few preventive rules are generally enough to avoid this:

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

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

Uproot and burn affected plants.

Onion rotten

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

Preventive action:

  • Do not add fertilizer to your onion plantations;
  • Preventively treat the soil with a decoction of undiluted horsetail;
  • Dry the bulbs well after harvesting.

Onion harvest

Harvest the white onions, fresh, in the spring when you need them.

Harvest colored onions in dry weather, when the leaves are 2/3 yellow (July-August).

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

Successful with your onion cultivation in the vegetable garden? On the contrary, does it cause you problems? Tell us all about it in the comments below…