How to Grow Onions

Onions are a popular bulb, commonly grown in gardens due to their versatility in cooking, ease of cultivation, and minimal space requirements. Additionally, the growing season for onions is relatively short, meaning you can start harvesting in spring, then dry and store them for winter use.

Select the type of onion to plant. Like most fruits and vegetables, onions come in various types, each with its own appeal for different reasons. Generally, onions come in three colors: white, yellow, and red/purple, each with its own unique flavor. Additionally, onions are categorized as long-day and short-day varieties. Long-day onions germinate when the day length extends between 14-16 hours (typically late spring/summer), whereas short-day onions germinate when the day length is between 10-12 hours (usually in winter/early spring).

• Long-day onions grow best in northern states of the U.S., while short-day onions thrive in the southern states.
• Yellow onions have a golden color and a mild sweetness. White onions are spicier and stronger in flavor than yellow onions, while red onions, with their purple hue, are often eaten raw rather than cooked.

Choosing the Method to Plant Onions. Generally, there are two popular ways to grow onions: from bulbs or from seeds. Gardeners often prefer planting from bulbs because they tend to be more robust and better able to withstand harsh weather conditions compared to seeds. However, if you have the right conditions and determination, you can successfully grow onions from seeds and then transplant them outside. Onions can be planted in soil when the weather is warm.

• You can also grow onions from cuttings or grafts, although this method is usually less successful and more difficult than planting from seeds or bulbs.
• Visit your local nursery to check which onion bulbs and seeds grow well in your area.

Identifying the Right Time to Plant. Onions can be tricky to grow if not planted at the right time. If onion bulbs are planted during cold weather, they may die or be more likely to flower compared to planting in the spring. When sowing onion seeds, it’s advisable to start them indoors at least 6 weeks before moving them outside. Make sure to plant the seeds 6 weeks before the last day of winter, then transplant them outdoors.

Choosing the Ideal Location. While onions aren’t particularly picky, they do require specific conditions to grow well. Choose a sunny, open space for planting. Onions thrive when given enough room to expand; the more space you provide, the larger the onions will grow. Avoid planting them in areas shaded by other plants.

• Onions can also grow well in raised beds. If you don’t have enough space in the garden, consider building a raised bed for planting onions.

Preparing the Soil. If you can prepare the soil a few months in advance, your onion harvest will be better. Ideally, begin preparing the soil and adding compost in the fall. If your soil is stony, sandy, or clayey, mix in some potting soil to balance it out. Additionally, you should check the soil's pH and add necessary compounds to ensure the pH level falls between 6-7.5.

• It's important to adjust the pH of the soil at least a month before planting so that any additives have time to work and establish the right conditions for onion growth.

Prepare the soil. When you're ready to plant onions, dig holes that are about 15 cm deep. Then, add a layer of phosphate fertilizer (1 cup for about 6 meters of soil). However, only add phosphate fertilizer if the soil has a low phosphorus content. Be sure to test the soil before planting. Use a 10-20-10 or 0-20-0 fertilizer mix to stimulate onion growth. Also, make sure to clear any weeds in the garden.

Dig the holes. Plant onions so that the soil above the bulb or seedling is no more than 2.5 cm deep. If the onion bulb is buried too deep, it might shrink, limiting its growth potential. Each onion bulb should be spaced 10-15 cm apart, and seeds should be sown about 2.5-5 cm apart. As the onions start to grow, you can replant or space them further apart to help them grow larger.

Plant the onions. Sow the onion seeds into the freshly dug holes and cover them with about 0.5-1 cm of soil. The bulb shouldn't be buried deeper than 5 cm. Use your hands or shoes to firm the soil above the bulb. Onions grow better when the soil is compacted. After planting, water the area lightly and wait for the onions to grow.

• Onions propagated by cutting need more water than those grown from bulbs or seeds, so you should add extra moisture if you’re using this method.

Caring for the onion garden. Onions are prone to damage because their root system is delicate and can be easily harmed by weeds or being pulled up. Use a hoe to remove any weeds without pulling them out completely, as this can damage the onion roots and hinder growth. Water the onions with about 2.5 cm of water weekly and fertilize them with nitrogen every month to provide extra nutrients. Right after planting, add a thin mulch layer around each onion to retain moisture and prevent weeds.

• If you want sweeter onions, you can water them more than usual.
• If your onions flower, it's a good idea to cut the flowers off. Flowering onions tend to not grow as large or flavorful.

Harvesting onions. Onions are fully mature when the tops turn a golden yellow. At this point, you can bend the tops over to the ground. This helps redirect nutrients to the bulb instead of the shoots. After 24 hours, the tops will turn brown and are ready to be harvested. Pull the onions from the soil, cutting off about 2.5 cm of the shoots and roots. Dry the onions under the sun for 1-2 days, then move them to a dry place indoors and continue drying them for 2-4 weeks.

• Store the onions in tights or mesh bags to improve air circulation while they dry. This method helps preserve the onions for longer and maintains their flavor.
• Sweet onions may spoil quicker due to their higher water content. Therefore, you should consume them sooner to avoid spoilage.
• If any onions show signs of rotting, discard or use them immediately to prevent the spread of disease to other stored onions.

• To encourage quicker growth of onions in your garden, plant the bulbs in a pot with moist soil for two weeks before transferring them to the garden. Keep the pot indoors until the onions sprout and develop roots, then move them outside to plant.
• To prevent pests and microorganisms from damaging your crops, consider planting radishes and onions together in the same garden.

• Onions can resist pests, but they may still be vulnerable to maggots eating the bulbs. It's recommended to use insecticidal soap according to the instructions to control maggots.
• Different onion varieties require different day lengths and usually prefer warmer temperatures. To ensure you're planting the right type of onion, it's best to purchase bulbs locally.