Home | Growing onions

Growing Organic Onions: Tips, Advice, and Secrets

Here are the essential tricks and secrets for growing truly organic, healthy, and high-quality onions without resorting to harmful pesticides.

by BioGrow

Growing Onions is a practice no self-respecting farmer can avoid, given its relative ease of cultivation and extended growing season. Onions are highly resilient vegetables widely used in Mediterranean cuisine, enjoyed both cooked and raw. One of the many advantages of growing onions is that the plant is not very attractive to pests. In this article, we will focus on this bulb and its methods of organic cultivation.

Of course, we will analyze all aspects of this vegetable, which is one of the most common in our garden and kitchen. But let’s start by looking at its origin.

Growing Onions: History, Properties, and Organic Cultivation


The onion (Allium cepa) is a bulbous vegetable belonging to the family Liliaceae. Together with its siblings, garlic and leek, it is among the first crops experimented by humans. The Egyptians were the first to cultivate onions around 3,000 B.C. The cultivar then spread with Magna Graecia and the Roman Empire throughout the Mediterranean basin, the true cradle of onion cultivation.

Nutritional Properties

From a nutritional standpoint, onions are highly dietetic. They consist of 90% water, 1% protein, and contain very little fat. They also provide essential minerals such as potassium (140 mg per 100 g), calcium (25 mg per 100 g), and phosphorus (35 mg per 100 g). Onions are also rich in vitamin A (3 mg per 100 g) and vitamin C (5 mg per 100 g).


There are numerous onion varieties suitable for cultivation in a home garden. The choice can be based on color (red, white, golden) or the intended use for consumption. Among the varieties, we distinguish between fresh onions and those left to reach full maturity.
One of the most appreciated varieties globally, proudly representing Italian and Calabrian production, is undoubtedly the Red Onion of Tropea IGP.

red Tropea onions

Red Tropea onions

The distinctive traits of this variety are its intense red color, due to its anthocyanins, which are sulfur-containing polyphenolic compounds; its special organoleptic qualities, namely, its particular sweetness and crispiness; and its oval-shaped form. These characteristics are the result of the plant’s genetic heritage shaped over centuries in the unique microclimate of Tropea, a small town perched on the sea. Tropea’s specific environmental influences make its onion a truly unique product in the world. Nowadays, the Red Onion of Tropea can be cultivated almost anywhere. Both organic seeds and seedlings in the nursery are quite common. However, when grown away from its native environment, the onion loses some of its distinctiveness (here you can find more detailed information about this specific variety).

How to Grow Onions

As mentioned, cultivating onions is not particularly challenging, and they have an extended growing season, which means they can be grown almost all year round, except during December to February.
The best time to grow onions like the Red Onion of Tropea is in the spring and summer. At the latest, they can be transplanted in September to ensure a harvest before winter. The choice of the best cultivation period will also depend on how you want to plant the onions. Different propagation methods exist for this plant.

Transplanting in Seedbed or Open Field

The quickest and safest method to grow onions is by transplanting bulbils from a seedbed, which are small mini onions that will be transplanted into the soil at a depth of about 5 cm.

Onions in a seedbed

Onions in a seedbed

Another method is to use sprouted onions that you may have stored during the winter in the cellar. You may often notice green sprouts in the onions you store. You can obtain a new bulb from these sprouts, perhaps a valuable variety that you purchased or cultivated earlier. To do this, gently separate the sprouted part from the rest of the vegetable. Once separated, the sprout should be planted in soft soil (with the sprout facing upwards).

Sprouted onions to clean up for transplantation

Sprouted onions to clean up for transplantation

This technique may be recommended for those who have balcony gardens. It’s easy to transfer our sprouted onions from the cellar to pots on our balcony.

Seed Sowing

Detail of an onion flower from which seeds are obtained

Detail of an onion flower from which seeds are obtained

Of course, it’s also possible to grow onions from seeds. In this case, the process will take longer, and sowing should take place at the beginning of autumn to allow the bulbs to enlarge by spring. In the spring season, thinning of the seedlings obtained from the seeds can be done, and finally, when you notice that the bulb has grown adequately, the harvest can take place.


Regarding climate, onion cultivars are highly resistant. The only climatic condition they fear is intense cold, so they are not cultivated in winter. However, exposure to sunlight is crucial, so it is advisable to prefer portions of your garden that receive ample sunlight.

Soil and Fertilization

To cultivate onions properly and have well-developed plants, you must work the soil. It should be loose, well-aerated, not too compact or clayey, and with a reduced amount of organic matter. It is essential to remember that it is NOT suitable to grow onions in freshly manured soil. With strong organic fertilization, excessive nitrogen can promote vegetative growth of the aerial part of the plant, to the detriment of the underground bulb, which is what we are most interested in. You can opt for a rotation that involves planting onions in areas manured the previous year, preferably after hosting heavier crops, such as tomatoes or zucchini.

Irrigation and Proper Spacing

For onions to grow, they need a moderate water supply. Onions do not thrive well in dry soils, but at the same time, they are sensitive to water stagnation. Therefore, it is essential to water carefully, using the drip hose system can be an excellent solution. For spacing, you should leave 10-15 cm between each onion on the row and 20-25 cm between rows, which is closer compared to other vegetables. After transplantation, it is essential to apply a good natural mulch, such as straw. This will limit the growth of weeds and keep the soil cooler.
Weeds take away much vital energy from our onions, which already grow in a more confined space, so pay close attention to cleanliness.

Pests and Diseases

Fortunately, onions are not very attractive to insects and fungi. As we mentioned, the main threat to onions is rot due to water stagnation. For the rest, aphids and mites tend to stay away. Many people even recommend adding onions to garlic macerate to create a more effective mix against pests.

Harvesting and Storage

Growing onions

Braided red Tropea onions

Harvesting onions can occur at different stages, depending on the variety and chosen cultivation period. The variation will also depend on your tastes and dietary preferences, of course. To determine if the onions have reached the desired maturity, simply dig the soil a bit and see if the bulb has enlarged. If you can’t resist the temptation to harvest, you’ll have a delicacy to use in various culinary recipes.
One method to accelerate bulb enlargement in the final phase of cultivation is to bend the stem at the base, without breaking it. This way, the plant’s vital energy will be concentrated in the lower part.
Regarding storage, if you have had a productive harvest, a commonly used method is braiding the onions. They can then be hung and stored in a cool, dry place, where they can last throughout the winter.
Finally, don’t forget the perhaps most important detail for obtaining high-quality onions in the following years: store some onions for sprouting. This way, you will have a foundation for your new cultivation.
That’s it. Now, happy onion cultivation!

Further Reading

  • Medical News Today – “Why are onions good for you?”: Onions may provide potential health benefits, including reducing the risk of cancer, improving mood, and maintaining skin and hair health. They belong to the Allium family and vary in size, shape, color, and flavor.
  • NCBI – “Onion (Allium cepa L.) is potentially a good source of important…”: Onion is a multi-use vegetable consumed fresh and in processed products. This article explores the various uses and benefits of onions.
  • PubMed – “Onions–a global benefit to health”: Onion (Allium cepa L.) is found across various latitudes and altitudes in Europe and Asia. This article explores the global health benefits of onions.
  • PubMed Central (PMC): Onion (Allium cepa L.) is potentially a good source of important antioxidants: This study analyzed six different cultivars of onions for various physico-chemical properties, including moisture content, sugar composition, and antioxidant capacity. The research found variations in these properties among different types of onions and highlighted the importance of the outermost layers, which contain the highest concentration of antioxidant compounds.
  • Phytother Res – “Onions–a global benefit to health.”: Onions have been traded widely due to their storage characteristics and durability. They are versatile and accepted by almost all traditions and cultures.
  • Nat Biotechnol – “Tear-free onions.”: A brief mention of tear-free onions, possibly related to genetic modification or specific cultivation techniques.
  • Crit Rev Food Sci Nutr – “Onion: nature protection against physiological threats.”: Onion is found in various regions and used for culinary and medicinal purposes. It’s often used as protection against physiological threats.
  • Prostaglandins Leukot Essent Fatty Acids – “Garlic and onions: their effect on eicosanoid metabolism and its clinical relevance.”: Both garlic and onion have been used as medicinal agents for thousands of years, with applications as antimicrobial, antithrombotic agents.
  • Int J Food Microbiol – “Black aspergilli in Brazilian onions: From field to market.”: This article discusses the occurrence of black aspergilli in onions, a group of fungi harboring potentially toxigenic species.
  • J Food Prot – “Water Application Method Influences Survival or Growth of Escherichia coli on Bulb Onions during Field Curing.”: This study examines how water application methods influence the survival or growth of E. coli on bulb onions during field curing.
  • Environ Monit Assess – “Determination of macro-, micro-element and heavy metal contents localized in different parts of three different colored onions.”: This research focuses on the determination of various elements and heavy metal contents in different parts of three colored onions.

Leave a Comment

* By using this form you agree with the storage and handling of your data by this website.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

Adblock Detected

This site stays alive thanks to the revenue derived from the advertising banners. By disabling your AdBlocker extension, you will allow us to continue offering free and high-quality content. Thank you.