Lettuce (Lactuca sativa) is the world's most popular salad green — an annual leafy vegetable in the Asteraceae grown on every inhabited continent and consumed by billions of people annually. From crisp, crunchy iceberg to tender, nutty butterhead, from upright romaine to peppery loose-leaf varieties, lettuce provides the crisp, refreshing foundation for salads across virtually every cuisine.
• Global production exceeds 27 million tonnes annually, with China producing over 50%
• Four main types: crisphead (iceberg), butterhead (Boston/Bibb), romaine/cos, and loose-leaf
• Lettuce is approximately 95% water — one of the most hydrating foods in existence
• The species name Lactuca derives from "lac" (milk), referring to the milky latex (lactucarium) that oozes from cut stems
• Ancient Egyptians were the first to cultivate lettuce from wild predecessors
• When lettuce bolts (goes to seed), the stems produce a milky sap that was historically used as a sedative — called "lettuce opium"
• Ancient Egyptians cultivated lettuce by 2680 BCE — it appears in tomb paintings from the 5th Dynasty
• Egyptian lettuce was tall, upright, and produced a milky latex — quite different from modern forms
• The Egyptians associated lettuce with the fertility god Min, likely due to its phallic shape and milky sap
• Greeks and Romans developed headed and loose-leaf forms
• Roman emperor Augustus reportedly built an altar to lettuce because he believed it cured his illness
• Columbus brought lettuce to the Americas in 1494
• Iceberg lettuce was developed in the 1890s in the United States and became the dominant type in the 20th century
• Romaine lettuce has experienced a massive resurgence due to the popularity of Caesar salad
• The genus Lactuca contains approximately 100 to 150 species
Roots:
• Taproot with extensive fibrous lateral roots, typically 15 to 30 cm deep
Leaves (the edible portion):
• Extremely variable across types:
• Crisphead (Iceberg): tight, firm, spherical head of crisp, pale green, heavily veined leaves
• Butterhead (Boston/Bibb): loose, soft head of tender, smooth, sweet, yellowish-green to green leaves
• Romaine/Cos: tall, elongated, upright leaves with a thick midrib, dark green, crisp, slightly bitter
• Loose-leaf: open rosette of tender, ruffled or smooth leaves in green, red, or bronze
• Stem lettuce (celtuce): grown for its thick, edible stem rather than leaves
Flower stalk (bolting):
• When triggered by warm temperatures or long days, the central stem elongates rapidly
• Produces a tall (60 to 150 cm), branching stem bearing numerous small flower heads
Flowers:
• Small, yellow, ligulate (strap-shaped petals), similar to dandelion flowers
• Self-pollinating
Seeds:
• Small, gray to black, with a white pappus (parachute-like tuft)
• Each flower produces 10 to 25 seeds
Per 100 g raw romaine lettuce (most nutritious type):
• Energy: approximately 17 kcal
• Carbohydrates: 3.3 g (including 2.1 g fiber)
• Protein: 1.2 g
• Vitamin K: 102.5 mcg (85% DV)
• Vitamin A: 8710 IU (436 mcg RAE, 174% DV)
• Folate: 136 mcg (34% DV)
• Vitamin C: 24 mg
• Potassium: 247 mg
Per 100 g raw iceberg lettuce (least nutritious type):
• Energy: approximately 14 kcal
• Vitamin K: 24.1 mcg
• Vitamin A: 502 IU
• Significantly lower in all nutrients compared to romaine or leaf lettuce
Key nutrients:
• Romaine and leaf lettuces are excellent sources of vitamin K and vitamin A
• Contains lactucarium — a mild sedative compound in the stems
• Red and bronze varieties contain anthocyanins
• Good source of folate, especially romaine
• All lettuces are extremely hydrating (95% water)
Planting:
• Direct-seed or transplant in early spring or late summer
• Sow seeds on the soil surface or barely covered (they need light to germinate)
• Thin to 15 to 30 cm apart depending on type
• Germination in 7 to 14 days at 10 to 20°C
• Succession plant every 2 to 3 weeks for continuous harvest
Site:
• Full sun in spring/autumn, partial shade in summer
• Rich, moist, well-drained soil, pH 6.0 to 7.0
• Consistent moisture is critical — drought causes bitterness and bolting
Care:
• Keep soil consistently moist
• Mulch to retain moisture and keep leaves clean
• Provide afternoon shade in warm weather to delay bolting
Harvest:
• Heading types: harvest when heads are firm and full
• Loose-leaf: harvest outer leaves as needed, or cut the entire plant 2 to 5 cm above the base
• Harvest in the morning when leaves are crisp and fully hydrated
• Store at 0 to 4°C — lettuce is highly perishable
• Salads — the primary and most universal use
• Caesar salad — romaine lettuce with Caesar dressing, croutons, and Parmesan
• BLT sandwich — lettuce is the essential "L"
• Lettuce wraps — used instead of tortillas or bread in many Asian cuisines
• Burger topping — the crisp, cool contrast to hot, savory meat
• In Vietnamese cuisine: as a wrap for spring rolls and bahn mi
• In Chinese cuisine: lettuce cups for stir-fried fillings ("san choi bao")
• In Korean cuisine: ssam (wraps) with grilled meats and ssamjang
• Juiced: green juice blends
• Grilled romaine — halved and charred briefly for a smoky salad
• Soup: wilted lettuce soup (wilted in butter and chicken broth)
Dato curioso
Ancient Egyptians revered lettuce so much that they dedicated it to Min, the god of fertility and reproduction. The Egyptians believed the plant's milky sap was an aphrodisiac — quite the opposite of lettuce's modern reputation as the most mild-mannered and unexciting of all vegetables.
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