What kind of onion should I grow - and how do I do it?

Onions come in many forms, but what they all have in common is that they are both useful and delicious. Here we guide you through different types of onions and give you tips for cultivation.

People have been cultivating onions for a long time. In China, onions were cultivated thousands of years ago, and there are also depictions of onions in the Egyptian pyramids. Here in the north, we grow a variety of onions today, ranging from green onions, which produce small, sweet onions on the top of a long shoot, to giant onions weighing up to a kilo. Regardless of which variety you choose, onions are full of vitamin C and an important flavoring in a wide range of dishes. Onions are also a fairly forgiving vegetable to store.

Common onions, like yellow onions, red onions, silver onions, shallots, and pickled onions can be stored at room temperature for several months – even longer if you store them dry and cool. Upward-growing varieties, like chives, spring onions, and leeks, can be frozen, but they can also be dried and used in herb salts and the like.

This is how you grow onions

Onions thrive best in a sunny spot, with loamy soil and regular watering. This way you will get the largest possible yield. Extra nutrients, preferably from manure water, and a little lime also help with growth, especially for leeks, which are one of the more demanding varieties. Leeks also typically grow well in sandy soil. When it comes to cultivating food onions, it is easiest to buy ready-treated onion sets, which are planted in well-fertilized soil as soon as the risk of frost is over in the spring.

The onions should be planted shallow, with a distance of about 10 cm. You can also sow food onions from seeds indoors, in March and April, which you can later plant outside. Feel free to use plant lighting and keep the fresh seedlings cool once they have started to sprout, around 15 degrees Celsius is ideal. For upright-growing onions like chives, leeks, spring onions, and scallions, it is best to start them indoors in the spring. Some varieties, like leeks, have a long development time and can be sown as early as late winter. Some onions, like scallions, may need a cold period to germinate. If the seeds have not sprouted after a month, you can try putting them in the refrigerator for the same amount of time - usually, the seeds will sprout as soon as they are exposed to warmth again. Read also How to get difficult seeds to sprout

Onion that gives you a bonus

If you grow shallots, which have a round and mild flavor, it can be fun to know that one single bulb can produce a cluster of up to eight bulbs. Shallots also come in an elongated variety, known as banana shallots.

As for garlic, which should be planted in late autumn – about two weeks before the first frost, one clove planted will yield a whole new bulb the following summer.

When should the onions be harvested?

Garlic is usually ready for harvesting when the stem bends down and turns yellow. Harvest them on a dry and sunny day, and let the onions dry in the sun for a few days before bringing them inside at room temperature. The onion stem is edible, but if you want the onion in the ground to continue growing, you should harvest very little of the stem that grows above ground. Upward growing onions, like chives, leeks, and scallions, provide a lot of onions with little effort, since they are often perennial. Certain varieties, like chives, can be harvested continuously throughout the season until the ground freezes, and can then be chopped up and stored in the freezer - or dried.

Onions help insects

The flowers of onions contain pollen and nectar that are beneficial for wild bees, hoverflies, butterflies, honey bees, and other useful small insects. Therefore, it is nice to let a small part of the chives, leeks, and other onions bloom. The flowering onions help to save many small insects that are unfortunately now threatened - besides, the flowers are beautiful in themselves.

Planting guide for different types of bulbs

Shallot
Pickled onion
Chives
Garlic