Growing onions at home: expert tips for planting, fertilising & harvesting onions

Growing onions at home: expert tips for planting, fertilising & harvesting onions

Onions go well with a variety of different dishes. Here you can learn everything you need to know about onion cultivation in your own garden.

The onion (Allium cepa) is one of the most popular vegetables. It belongs to the amaryllis family (Amaryllidaceae). Whether stewed, fried or raw, the onion is simply a must in many dishes. Even if its origin cannot be clearly defined and is somewhat of an unsolved mystery, it feels very much at home in the temperate latitudes of Central Europe. In the following, we will show you how to grow onions at home, what you need to know to take care of them and give you step-by-step instructions for onion harvesting.

Growing onions

Although onions can be cultivated from seed, most gardeners prefer to simply put onion bulbs into the ground to grow them. This is more convenient and usually more successful. In the next section, we discuss what is important to consider when planting onions.

Planting onion bulbs: the right location

Onions thrive best in loess and clay soils. The balanced amount and the constant supply of nutrients as well as the high proportion of humus make these soils the perfect location for onions. Those who do not have such ideal conditions for growing onions in their garden can incorporate compost into their onion bed. The most important thing is that the soil is deeply loosened. Loosening up stimulates soil life and aerates the deeper layers. This creates the best conditions possible for the onions to grow.

Tip: Would you like to grow onions in a container or on the balcony? No problem! The only thing that is essential is that the tub is large enough so that new bulbs can form.

When is the best time to plant onions?

You should not plant your onions before the end of April. The bulbs contain a lot of water and are therefore sensitive to cold. At the end of April, the risk of night frost is decreased, and the higher soil temperature ensures rapid growth of the young plants.

Note: Most of the time, it is the “summer” varieties of onion that are planted in domestic gardens. As described above, these should only be planted in April. Apart from that, there are also winter varieties that can be planted in August. The first bulbs are then usually harvested in late May.

How to plant onion bulbs?

The bed should be well loosened up before planting. Plant your bulbs deep enough so that the shoots just stick out of the soil. Plant at a distance of at least 15 cm in a row, leaving 25 cm between rows. Planting in rows also makes it easier to take care of your bulbs later on (while weeding etc.).

planting onions
Planting onions in rows makes it easier to take care of them [Shutterstock.com/yuris]

Planting onions in summary:

  • Loosen up the soil; if necessary, mix in compost (preferably in autumn!)
  • Sow onion seeds at the end of February or plant onion bulbs at the end of April
  • Do not plant the onion bulbs too deep; their shoots should be at the surface
  • Distance between rows 25 cm; distance within the row at least 15 cm
  • Regularly remove weeds to prevent competition

Buying onions vs. propagating onions

Buying onions

Cultivated onions are the safest way to a lush onion harvest. You can buy onions in any well-assorted gardening centre or order them conveniently online. Depending on the variety, you can purchase a bag of 250 grams of onions for as little as €1.80.

Growing your own onion bulbs

After the first year of cultivation you can propagate your freshly harvested onions yourself. Simply harvest and dry the bulbs as described above. Some onion varieties can also be propagated by division. This is done by cutting the tuber along the base of the shoot so that it is divided in the middle. It is crucial that both halves of the onion contain part of the shoot and root base, otherwise sprouting is impossible.

Note: The propagation of store-bought common onions is usually not very successful, as these vegetables have often been stored for a long time and also come from overbred varieties. During grafting, high-yielding and tasty varieties are placed on a resistant rootstock. Although it is possible to graft vegetables at home, this is very time-consuming and not always fruitful.

Propagating onions from seeds

If you want to accompany your onions from the beginning of germination, you can also buy onion seeds. The options are endless! A bag of onion seeds is very affordable and available from as little as €0.80 either online or in well-stocked local shops. Onion seeds can be sown directly in the garden in February or grown beforehand in a pot.

Tip: In order to not complicate things, it is best to just buy onion bulbs to grow more onions. These are very affordable and usually promise greater success of harvest than seeds!

Onion varieties: best varieties to grow and cook with

There is a large selection of onion varieties, so it can be overwhelming to choose from. We have compiled a small selection of different onion varieties for you below, where we briefly explain their differences:

Smaller and spicier onion varieties:

  • ‘Tonda Musona’: a white onion variety; very tasty and lasts long in good storage
  • ‘Rossa di Toscana’: a traditional heirloom red variety from Italy; round shape; intense flavour
  • ‘Zittauer Gelbe’: an heirloom onion variety; firm consistency; good flavour
  • ‘Texas Early’: late-ripening yellow variety; bears larger onions; abundant yields and good aroma

Large and mild onion varieties:

  • ‘Exhibition’: lush green shoots and abundant yields; aromatic; onions weigh up to 1.5 kg
  • ‘The Kelsae’: an English variety; very mild and large; record harvest: 6 kg onion!
  • ‘Alisa Craig’: an English variety; mild flavour; large onions (>700 g)

Onion plant care

The onion plant itself is relatively easy to care for. However, there are a few things you should pay attention to to ensure that the onion harvest is good. We will tell you what is important when it comes to onion care.

Fertilising onions

Onions are low to medium-yielding plants. Adding compost in autumn is the best way to enrich the soil with nutrients and positively influence its structure. After that, it is not necessary to add fertiliser. An excess of nitrogen in early summer can lead to an increased growth of the green onion shoots. Moreover, an overload of nitrogen can also cause a higher susceptibility to diseases and pests (e.g. onion fly).

Note: Depending on soil conditions, potassium and phosphorus fertilisation is sometimes recommended.

Watering onions

Onions prefer they soil to be moderately moist. When watering onions, you should make sure that there is no waterlogging. Depending on the weather conditions, regular watering at longer intervals is the best way to provide your onions with an adequate supply of water.

Harvesting and storing onions

Onions are a classic kitchen staple and are used for cooking all year round. In the next section, we discuss how to harvest, preserve and store onions so that they last long.

Harvesting onions

The onions are ripe and storable from the beginning of August. No gardening tools are required to harvest the bulbs. Simply pull your bulbs out of the ground by the leaves and place them side by side spread out on the ground. By storing them in this way, the outer skins of the bulbs can dry out over several days and thus become more durable.

Important: Turn your bulbs regularly while they are drying!

Storing onions

When the outer skins of the onions are dried, they can be stored. You can store your onions either hanging or lying down. To hang the onions, simply tie them together at the base of the leaves and hang them in a dark, cool and dry place.

storing onions
One of the best ways to store onions so that they keep for long is by hanging them in a dry place [Shutterstock.com/Martien van Gaalen]

Note: Do not store onions next to potatoes! Potatoes release a lot of moisture, which can be easily absorbed by dry onion skins.



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