How Do You Propagate An Onion?

Last updated on October 23rd, 2023 at 08:45 pm

Onions are one of the most popular and versatile vegetables. Whether raw, fried or stewed, they add a special flavor to many dishes. Cultivation and propagation in the home garden are unproblematic.

  • The onion (Allium cepa) belongs to the allium family (Alliaceae).
  • A distinction is made between table onions and vegetable onions
  • Vegetable onions are larger, mild and significantly heavier
  • Different colors, shapes, degrees of pungency and sweetness
  • Propagation by seeds and cuttings or bulbs possible

Propagate by sowing


Appropriate seeds can be purchased or obtained from existing specimens. To sow in the spring, they must be taken out of the ground in the fall of the previous year, along with the flowers, and hung upside down to dry. The dry inflorescences are then dried and stored in a cool, dry place during the winter. About a month before sowing, place them in a warmer place with temperatures of at least 25 degrees.

Zwiebeln im Gemüsebeet

How Do You Propagate An Onion?

Tip: To catch the seeds, for example, you can loosely pull a paper bag, not foil, over the inflorescences.

Perform germination test


Onion seeds usually remain germinable for up to three years. Nevertheless, not every seed germinates. Therefore, it is advisable to test the germination capacity before sowing. All you need is a bowl of water and the seeds.

  • Fill the bowl with water
  • Put the seeds into the water and wait for them to germinate.
  • Germinable seeds sink quite quickly to the bottom of the bowl
  • Non-germinable seeds float on the surface
  • Can be fished off there with a fine hair sieve
  • Then pour the water with the good seeds through a sieve.
  • Germinable seeds remain in the sieve
  • Let the seeds dry for some time and then sow them


Best time for sowing


The right time depends on the variety. Is it summer onions, winter onions, or to grow your own onions from seed? Summer onions are sown as early as possible, ideally from March to April, and winter onions between mid and late August. To grow your own onions, the seeds should be sown between the end of March and April.

Zwiebelernte zur rechten Zeit einbringen


In order to be able to harvest leeks as early as possible, a preculture is suitable for propagation. As early as mid-February, young plants can be sown on the windowsill or in a heated greenhouse.

  • To do this, fill small pots with growing medium.
  • Spread seeds on it
  • onions, four to six seeds per pot
  • Vegetable onions, one to two seeds
  • Insert seeds about one centimeter deep
  • Cover with substrate and moisten
  • In the greenhouse, row spacing of 20-30 cm is recommended


Depending on the variety of onion, the optimal germination temperature is 15-20 degrees and the germination period is between 14 days and three weeks. In the beginning, small, thin stalks appear. As soon as they are somewhat stronger, they can be separated or planted out to five to ten centimeters, depending on the variety.

Tip: To positively influence the development of the onions and to protect them from onion or carrot fly, a mixed culture with carrots is recommended.

Propagate via direct sowing


For a harvest in the same year, sowing in the garden should be done early and preferably in a sunny location and in loose, humus-rich and preferably unfertilized soil.

Steckzwiebel, Zwiebeln stecken
  • First draw grooves in the soil
  • About one centimeter deep
  • Spread seeds in them, not too densely
  • Cover with soil and press it down
  • Water carefully with a watering can
  • Germination occurs after two to four weeks
  • Separate young seedlings to onion thickness
  • Sow and harvest summer onions within a year.


Tip: Onions obtained by sowing usually have a longer shelf life than those obtained from bulbs. Late varieties in particular can be stored into March of the following year.

Grow your own onions


Onions for the coming year are sown directly into the bed at the end of April. Harvest the onions as soon as they have reached the size of a hazelnut. To be able to plant them next year, let them dry and overwinter them in a cold but frost-free and dry place. About four weeks before planting, move them to a warmer place with temperatures of at least 25 degrees.

Tip: This vegetable should never be planted or sown where leeks, chives, garlic or chives were previously planted (cultivation pause of at least five years).

Zwiebel im Beet

Propagate via bulbs


Winter onions for the spring harvest you put from August to October. They remain in the bed throughout the winter and mature in the spring. For summer onions for fall harvest, the timing is the same as sowing. Even though onions belong to the medium and low growers, fertilizer should not be applied. It is best to draw grooves again, it will facilitate the sticking. You stick them so deep that the upper third of the bulb is still visible. Finally, water the whole thing.

Frequently asked questions


Can germinating onions be used for new planting?


In principle, they can be planted like classic onions. However, it is not worth it, because no onion crop can be obtained from these significantly larger specimens. Only fresh green will form, which can be harvested and used.

Which is better, plugging or sowing?


Plugging onions is definitely the more convenient option. You save sowing and separating, because the already pre-cultivated onions only need to be plugged. However, plug onions are more expensive than seeds. In addition, onions that have been created by sowing have a much longer shelf life.

How to prepare the soil for the leeks?


The bed in question should be weeded and the soil well loosened. Already in the previous year is recommended to apply an organic fertilizer, but in any case do not fertilize before planting.

Author

  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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