Botanical Name: Allium cepa
Days to Maturity: 60 days
Native: Exists only in cultivation
Hardiness: Biennial grown as an annual
Variety Information: Mild, juicy, sweet, thin whites, with tender, edible, green tops (foliage), harvested early before it has the chance to form a bulb. 'White Lisbon' is a spring onion, generally used as a scallion-type onion. It has been in gardens since the 1700s.
When to Sow Outside: 4 to 6 weeks before your average last frost date or as soon as the soil temperature reaches 45°F, ideally 60°–85°F, and every 2 to 4 weeks recommended for continuous production. In Mild Climates, sow in fall for spring harvest.
When to Start Inside: 8 to 10 weeks before your average last frost date; transplant 4 to 6 weeks before your average last frost date.
Days to Emerge: 10–15 days
Seed Depth: ¼"
Seed Spacing: ½"
Row Spacing: 12"
Thinning: Not necessary unless thicker whites are desired
Harvesting: For repeated harvests of bunching onion greens, clip plants about an inch above the soil surface, and they will regrow. After cutting, apply fertilizer that is higher in nitrogen than phosphorus and potassium to encourage rapid regrowth. Bunching onions of the species Allium cepa can also form a bulb if given the time and space. To grow bulbs, harvest entire plants, leaving 3"-4" of space between the plants you want to remain and produce bulbs.