Ishikura Improved is a traditional Japanese bunching onion that delivers tender, mild green onions ready to harvest in just 60 days. Unlike standard onions, these plants grow as upright stalks with pristine white shanks stretching 20 to 24 inches long, topped with 6 or 7 thick, deep green leaves that look almost architectural in the garden. Grown in USDA zones 3 through 9, this frost-hardy annual thrives in full sun and moderate moisture, making it one of the most reliable cool-season crops you can grow. The real appeal lies in its temperature flexibility: it performs equally well in warm summers and cold snaps, even offering winter harvests in milder regions.
Full Sun
Moderate
3-9
30in H x ?in W
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Moderate
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These Japanese bunching onions produce remarkably long, elegant white shanks that set them apart from stubbier American varieties. The thick, deep green foliage sits upright and stays ornamental throughout the growing season. Because they tolerate both warm and cool temperatures without bolting or forming bulbs, they'll keep producing harvestable greens across seasons when other onions would stall.
Harvest these as green onions or scallions, using both the tender white shanks and green tops raw in salads, as a fresh garnish for soups and noodle dishes, or cooked gently in stir-fries. The long white portions are mild enough to eat raw and can be grilled whole for a sweeter, softer character. Unlike bulbing onions, every part of the plant is edible and useful, making these plants exceptionally efficient producers.
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Start seeds indoors 8 to 10 weeks before your last spring frost, sowing at a depth of 1/4 inch in seed-starting mix kept at 50 to 75 degrees Fahrenheit. Keep soil consistently moist until germination, which typically occurs within 7 to 10 days. Transplant seedlings outdoors once they've developed 2 to 3 true leaves and soil temperature reaches at least 50 degrees Fahrenheit.
Harden off seedlings over 7 to 10 days by gradually exposing them to outdoor conditions. Transplant once soil is workable in spring, spacing plants 6 inches apart in rows 18 inches apart. Bunching onions are frost-hardy, so light frosts won't damage transplants.
Direct sow seeds in early spring or late summer, pressing them lightly into moist soil at a depth of 1/4 inch. Keep soil consistently moist until seedlings emerge. Thin seedlings to 6 inches apart once they've developed 2 to 3 true leaves.
Begin harvesting when plants reach 10 to 12 inches tall, typically 60 to 69 days after sowing, by cutting plants 1 to 2 inches above soil level with a sharp knife. The white shanks should be firm and thick, and the foliage should be a vibrant deep green. Harvest outer leaves individually if desired, or cut the entire plant for continuous production. In milder climates (zones 7 to 9), you can leave plants in the ground and continue harvesting through fall and into winter, with plants responding to repeated cuttings by producing fresh growth.
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“Ishikura Improved traces its roots to Japan, where bunching onions have been cultivated for centuries as a staple vegetable. This particular cultivar represents generations of Japanese breeding focused on producing exceptionally long, white shanks and robust foliage, traits prized in Asian markets and kitchens. The 'Improved' designation reflects post-war refinements that enhanced cold tolerance and consistency, allowing the variety to thrive across wider geographic ranges. It arrived in North American seed catalogs as Japanese agriculture and seed exchange expanded in the mid-20th century, and it remains a favorite among gardeners who value heirloom Asian varieties and reliable, unbullying onion crops.”