VegetableOnion
Shonan Red Onion
Shonan Red Onion is a Japanese heirloom variety named after a region in Kanagawa Prefecture, prized for its exceptional flavor and crisp, sweet character. This cold-tolerant, open-pollinated bulbing onion reaches maturity in 160 days and grows 18-24 inches tall, thriving across zones 2-9 in full sun. Every part of the plant delivers genuine onion flavor, making it a standout choice for fresh eating and salads where its mild pungency shines without overwhelming the palate.
Photo © True Leaf Market
Growing Conditions
USDA Zone
2-9
Sunlight
Full Sun
Water
Moderate
Soil
Well-drained, Fertile Loam, Moderately Rich
Growth Stats
24 in
Height
Spacing
3
Plant Profile
Sunlight
Full Sun
Water
Moderate
Zones
2-9
Size
24in H x ?in W
Growth
—
Care
High
Hover over chart points for details
Highlights
The Shonan Red Onion earned its reputation through a remarkable balance of sweetness and crispness that works beautifully raw. Its Japanese heritage and intermediate-day bulbing habit mean it adapts well to diverse climates, from cool northern gardens to warmer southern ones. You can harvest and use the greens early on, then wait for the mature bulb to develop, essentially extending your harvest season from a single planting.
Common Uses
This onion shines in salads, where its crispness and gentle sweetness can be fully appreciated without cooking masking its delicate character. You can harvest the green tops early as scallions for a mild onion flavor, then allow the bulb to mature for slicing and eating raw or with minimal preparation. Its excellent flavor also makes it suitable for quick-cooking applications where you want to retain the onion's texture and subtle sweetness.
Growing Timeline
No timeline data available yet for this variety.
Care Instructions
Start Indoors
Start seeds indoors 6-8 weeks before your last spring frost to establish strong transplants. Sow seeds shallowly in seed-starting mix kept at 65-75°F, maintaining consistent moisture. Once seedlings develop their first true leaves, provide bright light and thin them so each has adequate space to prevent leggy growth.
Transplant Outdoors
Transplant hardened-off seedlings outdoors after the last frost date when soil has warmed to at least 50°F. Space transplants 3 inches apart in rows 15 inches apart. Handle seedlings gently to avoid damaging developing roots, and plant them at the same depth they were growing indoors.
Direct Sow
Direct sow seeds outdoors in early spring as soon as soil is workable, pressing seeds lightly into the soil surface since they need light to germinate. Thin seedlings to 3 inches apart once they develop their first true leaves.
Harvesting
Harvest the mature bulbs after 160 days when the tops naturally yellow and fall over, typically in mid to late summer depending on your planting date. Gently lift bulbs with a garden fork and cure them in a warm, dry, well-ventilated location for 2-3 weeks before storing. For early use as scallions, you can harvest green tops anytime after the plants reach 6-8 inches tall, cutting only what you need and allowing the plant to continue bulbing.
Growing Calendar
Enter your ZIP code to see a personalized growing calendar for this plant.
Companion Planting
Ecology & Traits
Edible
Scientific Classification
Allium cepa
Family
Amaryllidaceae
Genus
Allium
Native Status
L48 (I)
History & Origin
“This variety takes its name from Shonan, a coastal region in Kanagawa Prefecture, Japan, where it has been cultivated for generations. It represents the Japanese tradition of developing onions specifically suited to regional climates and culinary preferences, where mild, crisp onions are valued for fresh consumption and traditional preparations. The seed has been preserved and distributed through open-pollinated lines, allowing home gardeners and seed savers to maintain this heirloom's genetic integrity year after year.”