How To Grow Large Onions From Seed to Harvest

How To Grow Large Onions Guide

Here is how to grow large onions from seed to harvest even as a beginner gardener. I love growing different types of onions and using them in different recipes.

How To Grow Large Onions

Onions are a staple in kitchens worldwide, adding flavor and aroma to countless dishes.

However, there’s something special about harvesting large onions, they not only provide more yield but also offer a sense of accomplishment to the gardener.

In this easy-to-follow post, I’ll delve into the intricacies of growing large onions, covering everything from selecting the right varieties to harvesting and storing your bumper harvest.

Choosing the Right Onion Varieties

Not all onions are created equal when it comes to bulb size. Varieties such as ‘Ailsa Craig Exhibition’, ‘Kelsae’, and ‘Ailsa Craig’ are renowned for producing large bulbs.

Additionally, consider your local climate and day length requirements. Long-day onions require 14-16 hours of daylight, suitable for northern regions.

While short-day varieties thrive in regions with less daylight, like the southern United States.

Preparing the Soil

Onions prefer well-draining soil rich in organic matter. Before planting, conduct a soil test to assess pH levels and adjust if necessary.

Aim for a slightly acidic pH of 6.0-6.8. Incorporate compost or well-rotted manure into the soil to improve fertility and structure. Raised beds are ideal for onions, providing good drainage and warmth.

Starting Onions from Seed

Start onion seeds indoors 8-10 weeks before the last frost date in your area. Use shallow trays or seedling pots filled with a seed-starting mix.

Sow seeds thinly and cover lightly with soil. Maintain consistent moisture and provide bottom heat for quicker germination. Once seedlings emerge, ensure they receive adequate light to prevent leggy growth.

Transplanting Onion Seedlings

Harden off onion seedlings by gradually exposing them to outdoor conditions over 7-10 days before transplanting. Choose a cloudy day or transplant in the evening to minimize stress.

Plant seedlings 4-6 inches apart in rows spaced 12-18 inches apart. Set them slightly deeper than they were in their containers, covering the lower portion of the stem.

Irrigation and Fertilization

Onions have shallow root systems and require regular, consistent watering. Aim to keep the soil evenly moist, especially during bulb formation.

Apply a balanced nitrogen-rich fertilizer every 3-4 weeks to promote healthy foliage and bulb development. Avoid excessive nitrogen during bulb formation, as it can delay maturity and result in smaller bulbs.

Managing Onion Pests and Diseases

Keep an eye out for common onion pests such as onion thrips, onion maggots, and aphids. Practice crop rotation to deter pests and reduce disease pressure.

Mulching with straw or grass clippings can also help suppress weeds and maintain soil moisture. If pests or diseases become problematic, consider organic solutions such as neem oil or insecticidal soap.

Thinning and Pruning

Thinning is essential for allowing onions space to grow large bulbs. Begin thinning when seedlings reach pencil thickness, leaving 4-6 inches between plants.

Use scissors to snip off excess seedlings rather than pulling them, which can disturb the roots of the remaining plants.

Pruning onion tops when they reach 6-8 inches in height can redirect energy to bulb growth.

Providing Support and Protection

As onions grow, they may require support to prevent lodging, especially in windy conditions. Insert stakes or install trellises along rows to keep foliage upright.

Protect bulbs from sunburn by gently bending foliage over the bulbs or covering them with straw mulch. Row covers can also protect from pests and adverse weather conditions.

Harvesting and Storing Onions

Harvest onions when the tops have begun to yellow and fall over. Gently lift bulbs from the soil using a garden fork, taking care not to damage them.

Allow harvested onions to cure in a warm, dry, well-ventilated area for 2-3 weeks. Once dry, trim tops to 1-2 inches and store onions in a cool, dark place with good air circulation, such as a cellar or garage.

Troubleshooting Common Issues

Yellowing foliage, stunted growth, and rotting bulbs are signs of potential problems in onion cultivation.

Ensure adequate drainage to prevent waterlogged soil, which can lead to rot. Address nutrient deficiencies with balanced fertilizer applications.

Monitor for pests and diseases regularly and take prompt action to prevent outbreaks from spreading.

Final Thoughts

Onions are some of the easiest vegetables to grow and I highly recommend them for beginner gardeners who are just getting started in the game.

If you don’t get the onion harvest that you desire during the first try, don’t give up. Be patient and correct any mistakes you might have made the first time.

I would also recommend growing different vegetables so that if one fails another one will do well and you won’t feel discouraged.

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How To Grow Large Onions

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