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Growing Onions: A Simple Guide to Long Day, Intermediate Day, and Short Day Varieties

Onions are a versatile and flavorful addition to any garden. With their distinct taste and culinary uses, growing onions at home can be a rewarding experience. However, understanding the different types of onions and their specific growing requirements is essential for a successful harvest. In this guide, we'll explore the three main categories of onions: long day, intermediate day, and short day varieties. We'll delve into the characteristics of each type, how and when to grow them, fertilizer requirements, and when to harvest your crop.

Long Day Onions: Long day onions require approximately 14-16 hours of daylight to initiate bulb formation. These onions are typically grown in regions with higher latitudes, such as northern states in the United States or Canada. They are best suited for cooler climates, and usually overwintered because they are frost tolerant and need a long period of cold weather. Examples of long day onion varieties include Yellow Globe, Walla Walla, and Spanish Sweet.


To grow long day onions:

  • Start seeds indoors 8-10 weeks before the first frost date in your area. Use a well-draining seed starting mix.

  • Transplant the seedlings outdoors when the soil is till workable, before a hard frost arrives. Space the seedlings around 4-6 inches apart in rows with 12-18 inches of spacing between rows.

  • Provide consistent moisture and weed control throughout the growing season.

  • Long day onions are usually ready for harvest in mid to late summer when the tops start to yellow and fall over. Allow them to cure for a week or two in a warm, dry location before storing.

Intermediate Day Onions: Intermediate day onions require approximately 12-14 hours of daylight to initiate bulb formation. These onions are versatile and can be grown in a wider range of climates, including moderate temperature zones. They are suitable for regions like the central states of the United States. Popular intermediate day onion varieties include Candy, Red Candy Apple, and Super Star.


To grow intermediate day onions:

  • Start seeds indoors 8-10 weeks before the last frost date or directly sow seeds in the garden when the soil is workable.

  • Follow the same spacing and care instructions as for long day onions.

  • Intermediate day onions are usually ready for harvest in early summer. Harvest and cure them similarly to long day onions.

Short Day Onions: Short day onions require approximately 10-12 hours of daylight to initiate bulb formation. These onions thrive in regions with mild winters and shorter day lengths, such as southern states or tropical regions. They are typically grown during the late winter months into early spring. Some popular short day onion varieties include Texas Early Grano, Red Creole, and Bermuda.


To grow short day onions:

  • Start seeds indoors 8-10 weeks before the last frost.

  • Plant seedlings directly in the garden when the soil is cool and workable. Typically early spring.

  • Short day onions should be spaced 4-6 inches apart in rows with 12-18 inches of spacing between rows.

  • Provide adequate moisture and weed control during the growing period.

  • Short day onions are ready for harvest in early to mid-summer. Harvest and cure them similar to long day onions.


Fertilizing Onions: Onions generally require a balanced fertilizer with a higher nitrogen content (N) during the early growth stages to promote leaf development. Use a fertilizer with an NPK ratio of around 10-10-10 or 12-12-12. Apply the fertilizer according to the manufacturer's instructions, usually every 3-4 weeks.


Harvesting Onions: Onions are typically ready for harvest when the tops begin to yellow and fall over naturally. Once the tops have fallen, gently push the remaining foliage to the ground to allow the bulbs to mature and dry. Carefully lift the bulbs from the soil using a garden fork or shovel. Allow the onions to cure in a well-ventilated area for a week or two until the outer skins are dry and papery. Trim the tops and roots before storing the onions in a cool, dry location.


Growing conditions, onion varieties, and regional climate variations can influence the specific planting and harvesting times. It's advisable to consult local gardening resources or contact your local agricultural extension office for more precise recommendations tailored to your area.

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