Red onion is a staple vegetable found in nearly every garden. It has been cultivated for centuries, not only as a food ingredient but also for its medicinal properties. Today, we will delve into the process of growing red onions successfully. With the sowing season approaching, it is important to prepare, gather seeds, and plan the best location in the garden for optimal growth this year.
The soil plots designated for onion cultivation must be fertile, well-aerated, and possess good water retention properties. A slightly acidic to neutral soil pH level is ideal, ranging between 6 and 7. To maintain soil health, onions should not be planted in the same location for four consecutive years. Instead, they should be rotated after crops that have been fertilized with manure, leaving the plots free of weeds.
Red onions grow well following crops such as cabbage, carrots, peas, beans, zucchini, and other vegetables. Carrots are particularly beneficial as a companion crop because they protect onions from onion flies, while onions, in turn, safeguard carrots from carrot flies. This natural pest control method enhances the health and productivity of both plants.
For spring sowing, soil preparation should begin in the fall. Based on soil analysis results, a substantial amount of NPK fertilizer should be applied, favoring potassium and nitrogen. Once plowing and fertilization are complete, furrows should be closed using plates. Prior to sowing, additional NPK fertilizer should be incorporated in a 7:14:21 ratio to promote growth.
Proper soil preparation is crucial for successful onion cultivation. During the heading phase, KAN fertilizer should be applied in amounts of 100 kg/ha once or twice. However, excessive nitrogen fertilizers must be avoided as they can prolong the vegetation period and negatively impact bulb quality. The best organic fertilizer for onions is manure, ideally applied in the fall to enhance soil structure and nutrient content.
Before planting, burnt manure or humus can also be incorporated to improve soil structure and supply essential micro and macro elements. Potassium should be added to ensure healthy and resilient onion bulbs. Mixing manure thoroughly into the soil will keep it loose and suitable for sowing.
A crucial preparatory step before planting is the application of wood ash. This natural substance acts as a disinfectant, pest deterrent, and fertilizer. Wood ash is effective against snails, onion flies, and can enrich compost or improve soil quality. Since ash originates from burnt plants, it contains 13 essential nutrients required for plant growth, including calcium and potassium. It also neutralizes soil acidity, which is beneficial for onions as they thrive in non-acidic environments.
Numerous red onion varieties are available, each differing in purpose, sowing time, shape, color, bulb size, pungency, and disease resistance. Some varieties are cultivated for green onions, fresh consumption, or long-term storage. Depending on the variety and growing conditions, the vegetation period can range from 90 to 180 days.
Before sowing, carefully inspect onion sets and remove any that appear damaged, bruised, rotten, or soft. These unhealthy specimens will not sprout or yield quality bulbs. Red onions should be sown as early as possible in spring, as soon as weather conditions permit. Early sowing promotes vigorous plant growth, head formation, and reduces susceptibility to diseases and pests that could diminish yields.
Onion sowing typically occurs in February, March, or early April. Onion sets come in various sizes: less than 1 cm, between 1 and 2 cm, and larger than 2 cm. Medium-sized bulbs are preferred for planting, as smaller ones yield smaller heads, and larger ones tend to flower prematurely. To disinfect onion sets, they can be soaked in potassium permanganate solution or alternately placed in warm and cold water.
To accelerate germination, onion sets can be wrapped in a damp cloth and left for three days before planting. This jumpstarts the germination process and results in faster sprouting. In continental regions, onions are typically sown from late February to early April, depending on soil and air temperatures. The soil temperature should be at least 7°C to prevent slow germination or plant failure.
The optimal temperature range for red onion growth is 12 to 25°C. While onions are fairly resistant to low temperatures, young plants can endure brief exposure to -1°C, while mature plants can withstand -3 to -5°C. The minimum temperature required for germination is 2 to 3°C.
In traditional onion farming, onions are sown using sets. However, they can also be grown from seeds or seedlings. Red onions prefer sunny locations but can tolerate partial shade. They do not thrive in full shade.
Row spacing for onion planting ranges from 15 to 25 cm, depending on bulb size, with plants spaced 7 to 8 cm apart. If planted too densely, thinning is necessary. The ideal planting depth is up to 6 cm, with holes covered by 2 cm of loose soil.
Planting should be done in rows or pre-made holes using a wedge planter or stake, rather than pressing onions into the ground. Pressing can damage the bulbs, delaying sprouting. We created shallow channels, planted onions at even intervals, and gently pressed them into the soil for stability. Covering them lightly ensures even sprouting and growth.
Adequate watering is essential, particularly during early growth and spring development. Irrigation can be done using sprinkler or drip systems, with increased watering during dry periods. Weeds pose a challenge, especially with direct sowing, as they may outgrow and suppress onions. Regular hoeing and weeding should be performed until plants establish themselves. Careful hoeing is necessary to avoid disturbing shallow roots.
Typically, two to three rounds of cultivation are sufficient. The first occurs immediately after sprouting, the second follows two to three weeks later, and a third is done as needed. Mulching with straw helps suppress weeds, retain moisture, and reduce irrigation frequency, leading to high-quality, large onion bulbs.
Red onions are vulnerable to pests and diseases, including onion flies, moths, downy mildew, and rot caused by excessive rainfall. While wood ash provides preventive benefits, additional measures are required to combat other threats.
