Growing onions from seed


The sowing of white or red onions can take place at two times: from February to April or at the end of summer, until late September, while yellow onions are sown only in spring.

If we want to grow onions to preserve in vinegar, it is possible to sow from February until the whole summer.


Onion seeds need well-worked and aerated soil, they must be placed under a very light layer of earth (max 1 cm) which must then be compressed. If we opt for pot cultivation it may be a good idea to mix a dose of perlite into the chosen soil as the onion loves well-drained soil.

Fertilization must be moderate, the onion grows well in soil that is not excessively "rich". If the soil where we are going to sow is particularly depleted we can carry out a light mineral fertilization before sowing.

Whether you decide to grow our onions in the ground or in pots, it can be advantageous to germinate the seeds in a sheltered environment and then plant the germinated seeds in the ground spacing them about 20-25 cm apart so as to have a regular planting and avoid having to thin out after sowing. Alternatively, it is possible to sow the onions in seed trays and plant the seedlings when we see four or five leaves. We can make simple seedlings at home with recycled materials, for example egg cartons. The distance between the plants will be greater or smaller depending on the type of onion we decide to grow and the use we want to make of it: for canned onions or spring onions to be consumed fresh, a distance of 10-15 cm will be sufficient. The seedlings grown in the seedbed are buried covering them up to two cm above the root attachment.

We must remember that the onion loves the sun and the worst enemy of this vegetable is certainly humidity. We therefore choose soil without stagnation and well exposed. After germination we water sparingly and when the bulb is formed we suspend it.

Collection and conservation

The general rule for harvesting onions is that it is done when the leaves dry, however for fresh consumption the harvest can take place earlier, in spring/early summer or from July to the end of August for onions to be preserved. In the latter case, after harvesting, the onions must be left to dry in a protected place if the season is rainy or hung in the sun for a few weeks, until the leaves are completely dried, at this point it will also be possible to form braids. They can then be stored in a dark, dry and cool place, avoiding overlapping them.

Other tips

According to tradition, the onion is sown with the waning moon.

Generally we can expect to see the beautiful onion flowers two years after sowing, but sometimes abnormal weather conditions could stimulate the onion to flower early, in this case we must proceed to harvest the bulbs immediately even if they have not reached the desired size or we won't collect anything.

If we sow in the vegetable garden or recycle the soil from our pots, be careful not to plant onions where other onions or garlic, leeks, potatoes and cabbages have previously grown. However, it gets along well with nightshades, salads, carrots, chamomile and savory.

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