Food, Garden

How to plant onions from seed, seedlings, bulbs or sets

how to plant onions

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Outlines how to plant onions from seed, seedling, bulbs or sets with tips for position, care, harvesting and pest control of your onion crop.

Whether as an onion cake, roasted for roasting or steamed with vegetables – onions can be used in many ways in the kitchen. The good thing about onions is not just their characteristic taste: they contain many healthy substances such as vitamins and minerals. How to pickle onions: simple steps and easy recipes

Sulfur compounds give the vegetables an antibacterial and antiviral effect. The flavonoid quercetin is said to have a positive effect on the heart and fiber ensures a healthy intestine. Perhaps an onion milk or onion juice helped you with a cold? As you can see, the onion is not valued as a medicinal plant for nothing. However, some ingredients are lost during cooking.

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Onion origin

The kitchen onion (Allium cepa) belongs to the Amaryllis family (Amaryllidaceae) and is one of the oldest cultivated plants: It was cultivated in ancient Egypt and even served as a means of payment there. It is also one of the few vegetable plants whose origin has not yet been clarified. The most closely related wild plant has the botanical name Allium vavilovii and is native to Iran and Turkmenistan. Many botanists therefore assume that the wild form of the kitchen onion also comes from this region.

How to plant onions: overview

All onions are naturally perennial vegetables. Thanks to their thickened storage organ – the onion bulb – they are well adapted to a continental climate with strongly fluctuating precipitation and can survive dry periods well. A cross-section through the storage organ shows that it consists of a greatly shortened stem axis which is surrounded by many layers of storage leaves that have grown together. This means that the onion – like the more or less closely related onion flowers – can sprout quickly and form ripe seeds in a very short growing season.

Most hobby gardeners in the northern hemisphere grow the vegetables by planting onions in April and harvesting the onions in July or August. While this cultivation method is convenient, it severely limits the variety of the savory plant. Those who buy seeds can choose from many more varieties. Onions are divided into four groups: mild spring or spring onions , fine shallots , normal summer or kitchen onions and thick vegetable onions. Winter onions are rarely used, but there are many astonishingly cold-resistant varieties such as the popular ‘Stuttgart Giant’.

There are hardly any differences when it comes to cultivation, only the sowing dates vary. For fresh consumption and for storage, summer onions should be sown in March if possible. Spring onions can be grown in several batches from spring to autumn. The best time to sow winter hedge bulbs is the end of August to September, depending on the region.

How to plant onions: steps and requirements

Planting onion sets is a common method of growing onions in your own garden. By the way: even if onions and shallots look similar, they differ in a few ways. The difference between onions and shallots can be clearly seen, among other things, by their appearance and growth. While kitchen onions grow individually, shallots can be harvested in the whole bunch. They form groups of onions in the bed. Compared to the round kitchen onion with golden yellow skin, shallots are also more elongated to elliptical and available in different colors.

How to plant onions: Location and soil

All onions grow best in full sun, warm places in the vegetable garden. The soil should be loose, rich in humus and evenly moist. A certain amount of clay is an advantage, as the onion develops best with an even supply of water. If you have a pure sandy soil, you should ensure a high humus content over the years by regularly incorporating compost.

In the youth stage, onions are extremely sensitive, one secret of success is careful bed preparation: loosen the soil deeply with a sow tooth at least one week before sowing or plantingon. So the soil can settle well until the sowing. Work in three liters of compost per square meter and then cover the bed with fleece.

Tips for growing on the balcony: If you want to plant onions in pots, you will need a south-facing balcony. The onions and spring onions, for example, are best suited for this. In order for them to thrive, they need a planter with a volume of around ten liters.

How to plant onions: Crop rotation and mixed culture

If you want to grow the onion in your own garden, you should rely on a mixed culture in the bed. And do n’t forget crop rotation and crop rotation . These are important points in order to be able to harvest plenty of tasty and healthy vegetables. For example , if you planted leeks or onions in the previous year , you should not grow onions in the bed at this location for about four years.

Otherwise, the vegetables are much more likely to be attacked by pests or plant diseases. Carrots have proven to be ideal neighbors. But also beetroot or parsnips as well as cucumber and lettuce are suitable. On the other hand, you shouldn’t grow your onions next to cabbage, beans or potatoes.

How to plant onions: Sowing onions with seed or seedlings

“If you want thick onions, you sow them to Benedict” is an old farmer’s rule. March 21st is actually recommended as a sowing date. Onion seeds already germinate at temperatures around five degrees Celsius and benefit from the winter-moist soil.

  • You sow about two to two and a half centimeters deep and with a row spacing of 20 centimeters.
  • Separate the seedlings to the final distance of five to ten centimeters as soon as the leaves are about ten centimeters long.
  • Immediate sowing at the correct distance is not recommended because the germination rate of the seeds is usually well below 100 percent.

The large vegetable onions, which can weigh up to one pound, are cultivated in the Mediterranean region and do not grow any larger than normal onions in our climate. Unless they are preferred in a warm, bright place in February. The cultivation in pot plates with later planting out is practiced in commercial cultivation because of the poor germination rate and for early harvest, even with commercially available varieties.

In the garden, the method is particularly worthwhile on soils that dry out slowly in spring.

  • Lay out five to seven of the angular, black kernels per pot.
  • Put the seedlings and their roots in the bed when the third or fourth leaf appears.
  • In the beginning, the groups are a little tight. However, as the onions continue to grow, they will create the necessary space for themselves.
  • When sowing shallots in pots, three seeds per desired plant are sufficient.
  • Spring onions are sown or planted in the bed with closer spacing: three centimeters in the row and 15 centimeters in between are completely sufficient.

The sowing of winter onions for the harvest next May is carried out in the second half of August. However, cultivation is only recommended in milder regions, as the onions cannot tolerate excessive frosts. Before the onset of winter, the shafts should be at least as thick as a pencil. Tip: If the bed is still occupied, you can also prefer the winter onions such as vegetable onions in pots and later simply put them in the ground with the pot balls.

How to plant onions: Planting onions with bulbs or sets

If you plant onion bulbs or sets or seedlings in your garden, you must wait until there is no risk of late frosts. Only then should you put the onions in spring. This method is particularly suitable for regions in which soil and climatic conditions do not allow early sowing. The last cultivation date for winter onion sets is at the beginning of October.

All set onions – from the summer onion to the shallot to the winter onion – are placed about ten centimeters apart in the row and a row spacing of about 20 centimeters is maintained. Press the onions so deep into the soil that the tip just sticks out of the soil. The growing time for onion sets is around two to three weeks shorter than that of sown onions.

How to plant onion bulbs

Onion bulbs, often called onion ‘sets’ are small bulbs harvested in the first 12 monyths of an onion’s life cycle and stored during winter. They are easy to plant in your garden or pots, but often product smaller onions and are more often used to produce green onions than larger bulb onions.

You can see how to plant onion bulbs in this video:

How to plant onions: Caring for onions

Regardless of whether it is sown, planted or preferred: Weeding is one of the most important maintenance tasks in onion cultivation – especially during the youth stage. But be careful not to pull the young vegetables out of the ground. As soon as the shaft thickens, the water requirement increases: Don’t forget to water not only when growing in summer, but also on sunny autumn days. It is best to water in the morning and moderately.

Onions intended for storage are not watered for two weeks before harvest so that they mature completely. Adding additional fertilizer in summer is not forbidden, but it is also not absolutely necessary. Onions are medium to low eaters and are quite frugal: They usually get by with the nutrients that the compost provides, which was worked into the ground in spring. Too much nitrogen in the soil tends to make the plants fattening and difficult to store later.

How to plant onions: Harvest and recovery

In order for the cultivation to be worthwhile and to be able to feed on the spicy vegetables for a long time, the onions must be harvested and stored correctly . The ideal time for harvesting stored onions has come when the leaves twist and turn yellow by themselves and the leaf roots dry out. A good guideline is: around two thirds of the vents should be kinked.

The turning of the leaves, which is still often practiced in many gardens, does not accelerate ripening and is only useful in exceptional cases. On nutrient-rich soils or in persistently damp weather, the plants form many leaves and become very tall – in such cases you can help a little. Despite careful drying, the onions that are forced to ripen contain more water and are less storable.

Be careful when harvesting the onions: it is best to carefully loosen the soil with a digging fork before pulling the vegetables out of the ground. In dry summer weather, leave the harvested onions on the bed for a few days so that the skins dry off.

Alternatively, you can braid the yellowed foliage into braids. Then hang the onions in an air-dry and rain-protected, not too cool place to dry. Braided like this, they can also be stored.

Do not keep the stored onions in the refrigerator, because the cold stimulus will cause them to sprout again very soon. They keep the longest in a light, dry attic or in a boiler room that is not too warm at temperatures around 15 degrees Celsius.

Onions can also be stored in shallow boxes or hung in cotton bags. The important thing is: do not keep them in the same room as potatoes! The tubers release moisture to the onions, which can rot from the inside out.

How to plant onions: Winter protection

You should have a fleece ready for winter onions if the temperatures at the end of the season are well below zero. If there is freeze below five degrees Celsius, the bed is covered for safety. Light protection with fir branches also prevents the leaves of the plants from drying out in the cold east wind.

Onion varieties to try

There is a great variety available for growing onions in your own garden. Especially when buying seeds. Only a few are available as onion sets. Overall, the varieties vary in shelf life, taste, size, shape and color. We give you a small overview of the groups mentioned above:

Summer onions

  • ‘Stuttgarter Riesen’ is a well-tried and traditional variety with large, flat-round onions. They can be stored well, are medium hot and taste spicy.
  • ‘Zittau Yellow’ delivers a rich harvest and is well known among vegetable gardeners. The round onion has a strong aroma and has a long shelf life.
  • ‘Roter Laaer’ is a storable, purple-red variety with a flat, round onion that can be eaten directly, but can also be stored. Their white flesh is crossed with red rings.
  • ‘Piroska’ forms a medium-sized, broad onion. It is mild in taste and has a dark, blood-red skin. It is considered to be robust and can be stored for a long time.

Large onions

  • ‘Ailsa Craig’ produces large, usually round, juicy onions. With sufficient preculture, the variety is considered to be very productive and can also be stored until around December.
  • ‘Valencia Temprana’ is a large, precocious vegetable onion from Italy. The meat is firm and sweet, but the onion cannot be stored well.

Winter onions

  • ‘White Queen’ is a winter onion that forms medium-sized, finely aromatic onions when sown in spring. They are easy to put in, but cannot be stored.

Spring onions

  • ‘Baja Verde’ is a fast growing variety and does not make onions. The green and white shafts taste spicy and go well with Asian dishes.
  • ‘Elody’ is resistant to cold and has snow-white, mild onions. You can sow them in spring or summer.


  • ‘Laaer Rosa Lotte’ is a tried and tested Austrian variety with pink meat and a mild taste.
  • ‘Yellow Moon’ is robust, grows quickly and has round, yellow onions with a mild, piquant aroma.

How to plant onions: Propagating onions

Onions can be propagated using onion sets or bulbs. The single onion, in turn, can be multiplied by its brood onions, which it forms on its stems that grow upwards. A pole division is also possible. The clumps of the spring onions can also be divided.
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Diseases and pests

One of the most common pests is the onion fly , the larvae of which live in the storage tissue and render the onion unusable. It can be fended off by a mixed culture with carrots, but only protective vegetable nets are reliable protection . Downy mildew also appears on onions. Incorrect care and cool, damp weather favor the fungal disease . Some types of onion, such as shallots, multi-layer onions and winter onions are generally considered to be more robust than the kitchen onion. However, they are not completely immune to diseases and pests .