Onion: planting, growing, caring for and harvesting

Onion is widely used as condiment in cooking, but it is also consumed as vegetable when it is for example stuffed. All varieties of onions are appreciated, whether it is the baby onion, or large white, red or yellow onions … To always have some on hand and enjoy its health benefits, you might as well grow it in the garden. Here are the tips to follow for successful planting or sowing, and meet all the needs of this condiment and vegetable from the family of Amaryllidaceae in order to benefit from an abundant harvest.

Planting onions

Before planting onions, it is essential to smoke the earth which must be sufficiently rich to promote production.

We can buy the onion bulbs in specialist shops from the start of the year. They are ready to be transplanted. This facilitates the work of the gardener who is then exempt from the seedlings that we will discuss in the second part, and in this way he benefits from a earlier harvest.

For a successful onion plantation, it is advisable to first dig furrows spaced about thirty centimeters apart and whose depth is limited to 1.5 cm.

People who garden with the moon will plant the onions in the ascending moon, also known as the rising moon, during the Root days and will harvest on the descending moon. This advice also applies to sowing onions.

Sow your onions

Onion (Allium cepa) is a plant that is grown as an annual although it is, in the wild, a biennial plant. His edible bulb appears in the first year and must be harvested. But if it remains in the ground, it will develop in the second year a tall stem bearing a beautiful inflorescence white. It is this flower that provides capsules containing the seeds that can therefore be recovered to carry out their own sowing of onions.

To succeed in sowing, you have to remember this:

  • White onion is perfect for a winter culture although it does not keep much longer than colored onions. The fall sowing, are in fact between August 15 and September 15. They are carried out in the nursery on the fly, then the young plants are to be transplanted in place around 15/20 October, that is to say when the leaves are about 18 cm.
  • The spring sowing are in place, between March and May, and mainly concern small white onions that are preserved in vinegar in order to consume them as condiments.
  • Colored onions can be sown in place from the beginning of spring in all regions of France for a harvest from the summer. On the other hand, it is only in the areas located in the South that they can be sown just before autumn, between mid-August and mid-September, to benefit from its harvest the following spring.
  • Baby onions are sown online or broadcast in April and May, for a harvest in September.

You have to sow a seed every 2 cm and then cover your seedlings with only a small centimeter of soil. About 11 days after sowing, the onions begin to rise.

About ten weeks after sowing, a first thinning at 5 cm and then three or four weeks later, a second thinning is necessary, this time at about 14 cm. The shoots that are taken out of the rows can easily be eaten with a peppery white cheese or chopped fresh herbs, or even cut into sections and incorporated into a mixed salad.

Growing onions

Onions like light soils that are not too loose, rich in manure and well drained. He hates excess humidity. It is preferably installed in a warm and sunny situation. It is recommended to grow several varieties of onions in order to harvest throughout the year, knowing that only colored onions can be stored all winter.


It’s not only in dry weather that we sprinkle the onions. Another important point to respect: do not water if you have to harvest in the next three or four weeks.


The colored onions need inputs in nitrogen-rich fertilizer once during thinning then a second time four weeks later. We then take advantage of a hoeing session to fertilize the soil.


The onion growing space should always be impeccable. It is therefore essential to weed frequently with a hoe or by hand between the rows and at the base of the plants. Using the hoe also helps aerate the soil.

Parasites and diseases

The onion fly is to be feared when one does not practice crop rotation. It is therefore strongly recommended to grow onions only once every four years in the same area of ​​the vegetable garden. An invasion of white larvae of this parasite forces all the affected bulbs to be destroyed without delay.

Under very good growing conditions, onions are not particularly sensitive. A excess humidity promotes certain diseases. This is mainly the gray rot caused by Botrytis (a fungus), sclerotiniosis also called white rot, or even mildew. Too acidic soil can also cause problems.

Good and bad associations

Onion can be paired with the garden with strawberries, carrots, beets, parsnips, cucumbers, lettuce and tomatoes. It should not be grown too close to peas, broad beans, beans and other legumes or even close to the potato.

Harvesting onions from the garden

It is in the spring that the white onion is harvested. Keeping for a short time, it should be consumed quickly. As for colored onions, they are harvested in dry weather, during the summer season, from July until the end of September, as soon as their leaves are dry. We provide ourselves with a fork-spade to dig up the onions with delicacy because if they are bruised they will not keep. It is advisable to let dry between 24 and 72 hours in the sun, or if there is a risk of rain, under an awning or in the basement for example. They can be stored for several months in a dry room where there is a absolute darkness so that the onions do not germinate. They can be stored in wooden crates. But we can just as easily suspend them. To do this, it is necessary to make boots thanks to the braiding onions, as our elders did.