Senshyu onion

Senshyu Onion Seeds (Allium cepa) – Japanese Overwintering Variety

Senshyu Onion is a traditional Japanese heirloom prized for its sweet, mild flavor and distinctive golden-yellow skin. Bred for overwintering, this hardy variety is also proving highly adaptable for spring sowing in cooler climates like Ireland, making it a versatile and rewarding choice for home growers.

Key Features:

• Origin: Japanese heirloom introduced to the UK in the 1970s

• Type: Long-day onion grown from seed

• Flavor: Mild and sweet – ideal for cooking, salads, or storage

• Storage: Excellent – keeps well for several months

• Days to Maturity: ~160–180 days

 Adapted for Irish Growing Conditions

While traditionally sown in autumn for overwintering, Senshyu Onion has been trialed as an outdoor summer crop in Ireland. In this approach, seeds are sown indoors in late January to early February and transplanted outdoors once conditions allow. Harvest typically occurs in July, offering an earlier crop than many other varieties.

 Growing from Seed:

• Start Indoors: 8–10 weeks before last frost (late Jan–early Feb recommended), 3-4 seed per module

• Transplant Outdoors: When seedlings are strong and soil is workable

• Soil: Fertile, well-drained, pH 6.0–7.0

• Sunlight: Full sun essential

• Watering: Keep evenly moist; avoid waterlogging

• Fertilizer: Apply balanced fertilizer at planting and mid-season

• Harvest: When tops fall over and begin to dry (typically in late July)