Summer Island Onion is a frost-hardy bulbing onion that thrives across hardiness zones 3 to 10, making it a reliable choice for gardeners in nearly every climate. This cultivar of Allium cepa produces quality bulbs when direct seeded or transplanted, with tight spacing requirements that encourage efficient garden use. The catalog sources emphasize careful transplanting technique and photoperiodic management, revealing a variety that rewards attentive growing with reliable harvests.
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High
3-10
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Moderate
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Summer Island Onion performs as a true photoperiodic bulber, meaning it responds precisely to day length rather than guesswork. The catalog recommends direct seeding with careful thinning to the strongest seedlings, then transplanting into shallow trenches for superior root establishment. Its frost-hardy nature extends the growing season in spring and fall, while the tight 2-inch spacing allows you to produce more bulbs per square foot than many other onion varieties.
Summer Island Onion grows as a full bulbing onion suited to storage and year-round kitchen use. The variety can be harvested earlier as larger scallions or left to mature fully into storage bulbs. Mature bulbs can be cured and stored for extended periods, making them valuable for preserving summer harvest through winter months.
No timeline data available yet for this variety.
Sow 10 to 12 seeds in a 4 to 6 inch pot at temperatures between 50 and 70 degrees Fahrenheit. If seedling tops exceed 5 inches before transplanting, cut them back to 3 inches to encourage stockier growth. Time indoor seeding so transplants are ready when outdoor soil warms.
When transplanting, carefully separate seedlings and place them in a shallow trench, spacing them 2 inches apart in rows 12 inches apart. Fill the trench around seedlings and water in well. Transplanting into trenches rather than standard rows helps establish superior root systems.
Direct seed and thin to the strongest plant when seedlings reach 4 to 5 inches tall. This method works well for Summer Island Onion and avoids the shock of transplanting.
For scallions, harvest when plants reach pencil size or larger, then wash, trim roots, and store. For full bulbs, allow foliage to mature completely, then after about half the tops have naturally fallen over, push over the remainder and wait approximately 1 week before harvesting. Loosen soil around bulbs before lifting to reduce damage. Always harvest in dry weather; remove any bulbs that have sent up flower stalks, as these will not cure properly.
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