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Onions - Key Growing Information
CULTURE: Onions require full sun and fertile, well-drained soil with a pH of 6.0–7.0. Sandy loam soils are ideal; in heavier soils, use raised beds or raised rows to promote soil drainage.
DAY LENGTH: Onion bulbing is triggered by day length, and maximum day length during the growing season increases from south to north. Short-day onions are grown at lower latitudes in the South, while intermediate and long-day onions are grown at higher latitudes. Refer to "Adaptation" in each variety description for details.
DIRECT SEEDING: In April or early May, or as soon as the soil can be prepared in early spring, sow in a 2" wide band, about 2 seeds/in., 1/4– 1/2" deep, rows 12–18" apart. Thin to 1 1/2–2" apart for highest yields in fertile soil. Thin to 3-4" apart for larger onions.
TRANSPLANTING: In long- and intermediate-day areas, sow indoors 6–8 weeks before last frost date. Sow 128-cell trays, 1 seed/cell, and cover with 1/4" soil. Transplant 4" apart in rows 12–18" apart. Unruly tops may be clipped to 5" at time of transplant.
CULTIVATION: Keep onions well weeded with shallow cultivation.
WATER: Onions are shallow-rooted and grow best with at least 1" per week of rain or irrigation, especially during the bulbing phase.
DISEASES: Adequate air circulation and crop rotation aids in reducing the risk of foliar disease.
HARVEST: When necks become soft and 50% of tops are falling over, pull and cure in well-ventilated space out of direct sunlight (to prevent greening) or sun-cure in field for 2–7 dry days before moving to dry location. Cure until tops are completely dried; about 2 weeks.
STORAGE: When dry, clip off tops and roots and store in onion bags or shallow boxes at near freezing and 65–70% humidity.
DAYS TO MATURITY: From direct seeding; subtract 10–15 days for days to maturity from transplant.
AVG. DIRECT SEEDING RATE: 1 oz./25', 1M/50', 5M/250', 25M/1,250', 580M/acre at 20 seeds/ft., in rows 18" apart.
TRANSPLANTS: Avg. 1 oz./4,900 plants, 1 lb./78,750.
SIZED SEEDS: Standard on all varieties.
SEED SPECS: SEEDS/LB.: 96,900–127,700 (avg. 112,000).
PACKET: 250 seeds, sows 12' or makes 140 plants.