Botanical Name: Lactuca sativa
Days to Maturity: 20–25 days
Native: Unknown; lettuce has been in cultivation a long time.
Hardiness: Frost-tolerant annuals
Variety Information: BUTTERHEAD LETTUCE: BUTTERCRUNCH: Soft, slightly crumpled light green leaves in a loose head, often with a creamy yellow core. LEAF LETTUCES: RED SALAD BOWL: Deeply lobed red leaves. RED SAILS: Dark red, crinkled leaves with frilly edges, slower to bolt, an All-America Selections winner. ROMAINE LETTUCES: ROUGE D'HIVER: Green leaves tinged with reddish-brown; rich, buttery flavor. PARRIS ISLAND COS: Upright growth with medium green, slightly savoyed (crinkled) leaves, crisp ribs, and buttery-green heart.
When to Sow Outside: 2 to 4 weeks before your average last frost date, when soil temperature is at least 40°F, ideally 60°–70°F. Successive Sowings: Every 3 weeks until 2 weeks before your average first fall frost date.
When to Start Inside: RECOMMENDED. Sow indoors any time of year, with indoor temperatures 60°–75°F. Successive Sowings: Every 2 weeks for a continual supply.
Days to Emerge: 5–10 days
Seed Depth: ½"
Seed Spacing: ¾"
Thinning: Not required
Harvesting: When seedlings emerge, the first pair of leaves to show are the cotyledons, which can look very different from the leaves that follow, called "true" leaves. Market Day Lettuce baby greens are ready to harvest when they have true leaves, at 2"–4". Slow growers, or cool growing temperatures may require more time. Harvest by cutting just above the soil line. For more than one harvest (up to 3 before flavor declines) leave about 1/2" of leafy growth on the small plants so they can regenerate.