Cortland Onion is a long-day bulbing onion bred for cold climates, thriving in hardiness zones 3 through 10 and reaching maturity in 110 days from direct seed. This cultivar's exceptional frost-hardiness makes it a reliable choice for northern gardeners who want substantial, storage-worthy bulbs rather than quick-maturing scallions. It demands consistent moisture and well-balanced soil to develop its characteristic firm bulbs, rewarding careful attention with dependable harvests even in short-season regions.
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Cortland's cold-hardiness sets it apart as a variety built for challenging climates where many onions struggle to reach full size. The 110-day maturity window positions it perfectly for gardeners working with shorter growing seasons, while its high water needs and preference for neutral soil (6.0 to 7.0 pH) signal that this is a variety that rewards precision. Direct seeding at tight 2-inch spacing within 12-inch rows creates densely productive beds, and the photoperiodic nature of onion growth means Cortland will wait for the right day length before bulking up, rather than bolting prematurely.
As a storage onion, Cortland excels in long-term preservation, making it invaluable for gardeners who want to extend their harvest into winter months. The firm bulb structure and reliable curing capability support traditional storage methods, from root cellaring to cool pantry storage. This variety suits any kitchen use where shelf-stable onions are preferred over fresh scallions.
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Sow seeds indoors in pots 4 to 6 inches across, planting up to 10 to 12 seeds per pot. Keep soil temperature between 50 and 70 degrees Fahrenheit for germination. When seedlings reach 4 to 5 inches tall, thin to the strongest plant. If tops exceed 5 inches before transplant time, cut them back to 3 inches to promote vigorous root systems. Plan to transplant after the last frost in your zone.
When seedlings are ready to move outdoors, carefully separate them and place in a shallow trench, pressing soil firmly around each seedling and watering in thoroughly. Space plants 2 inches apart within rows spaced 12 inches apart. Transplant after frost danger has passed, in zones 3 to 10.
Direct sow seeds in spring once soil is workable and reaches 50 to 70 degrees Fahrenheit. Sow seeds thinly and thin seedlings to 2 inches apart when they reach 4 to 5 inches tall.
Harvest begins around day 110 from direct seeding, once you observe that approximately half the tops have fallen over naturally. At this sign, push over any remaining upright tops and wait about one week before harvesting. Choose a dry day for harvest, as onions harvested in wet weather cure poorly and are prone to rot. Loosen the soil around bulbs gently to encourage them to lift freely and allow the protective paper to dry completely.
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