How to Grow Cos Lettuce Paris Island
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Cos Lettuce Paris Island
Lactuca sativa var. longifolia
vegetableParis Island Cos, also known as romaine lettuce, is a crisp, upright-growing lettuce variety with elongated leaves and a tender heart. Named after the Mediterranean island of Cos, this heirloom variety is prized for its excellent flavor, crunch, and traditional Caesar salad applications. It grows in a tight head formation with dark green outer leaves and pale, blanched inner leaves.
When should you plant Cos Lettuce Paris Island in your zone?
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Example Cos Lettuce Paris Island timeline · Pittsburgh, PA (Zone 6b)
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Plant Cos Lettuce Paris Island
Around Apr 17Near Pittsburgh's average last spring frost.
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Tend & protect
Late spring–summerWatering, feeding, and pest-watch reminders.
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Harvest Cos Lettuce Paris Island
Around Jun 16≈ 60 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Cos Lettuce Paris Island dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 3-9; cool-season crop best grown in spring and fall
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Get my Cos Lettuce Paris Island timeline →Growth Stages
Germination & Seedling
2-3 weeksSeeds sprout in 7-10 days at 65-70°F. Tiny seedlings develop their first true leaves, appearing delicate with cotyledons followed by serrated leaf edges.
Maintain soil moisture without waterlogging. Ensure bright light (grow lights if indoors). Thin seedlings to prevent crowding. Maintain cool temperatures (65-70°F).
Vegetative Growth
3-4 weeksPlant develops 4-6 true leaves and forms a low rosette. Leaf production accelerates with increasingly serrated, elongated leaves in green to dark green coloring.
Thin to final spacing if direct seeded. Water consistently and deeply. Apply balanced fertilizer every 2-3 weeks or side-dress with compost. Monitor for early pest issues.
Head Formation
2-3 weeksLeaves begin clustering upright into a loose, then increasingly tight head. Outer leaves grow large and dark; inner leaves remain pale and tender.
Continue consistent watering—this is critical for head quality. Maintain cool temperatures (60-70°F optimal). Reduce nitrogen to favor head firmness. Remove any damaged outer leaves.
Maturity & Harvest-Ready
Ready to harvest; window lasts 1-2 weeks before declineHeads reach 8-10 inches tall with firm, well-formed structure. Inner leaves are pale, crisp, and sweet. Head resists bolting if temperatures remain cool.
Heads can be harvested at this stage. Continue watering to maintain crispness. Harvest before sustained hot weather triggers bolting. If not harvested, maintain moisture and coolness.
Bolting (if temperatures rise)
1-2 weeks before seed setPlant produces a central flower stalk with yellow flowers and developing seeds. Leaves become bitter and lose tenderness. Head loosens and elongates upward.
Harvest immediately if bolting begins, as lettuce becomes inedible. Provide afternoon shade in summer. Plant later-season crops in fall for best results.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Spray with strong water spray; use insecticidal soap or neem oil; encourage natural predators like ladybugs and lacewings
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Rotate crops; use floating row covers; apply beneficial nematodes to soil; grow resistant varieties
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Handpick; use copper tape or barriers; apply diatomaceous earth; beer traps; remove garden debris
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Use yellow sticky traps; spray neem oil or insecticidal soap; encourage parasitic wasps
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Improve air circulation; avoid overhead watering; remove infected leaves; ensure proper spacing
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Plant resistant varieties; space plants well; water at soil level; remove affected leaves; apply sulfur dust if needed
Uses
Caesar Salads & Fresh Cooking
CulinaryParis Island Cos is the traditional choice for Caesar salads, prized for its crisp texture, upright leaves that hold dressing well, and slightly sweet flavor. The tender inner leaves are ideal for fresh eating, while outer leaves work well in cooked applications. [source]
Sandwich & Wrap Lettuce
CulinaryThe firm, elongated leaves of Paris Island make excellent wraps and sandwich layers. Individual leaves can be used to replace tortillas or bread for low-carb meal options. [source]
Dietary Fiber & Minerals
MedicinalRich in fiber for digestive health and contains valuable minerals including potassium, magnesium, and iron. Low in calories with high water content, supporting hydration and weight management. [source]
Micronutrient Source
HouseholdContains significant amounts of vitamins A, K, and C, along with folate and antioxidants that support immune function and overall wellness when consumed fresh. [source]
Garden Biodiversity
WildlifeFlowering plants (if allowed to bolt) provide nectar and pollen for bees and beneficial insects. The dense foliage offers shelter for ground-dwelling beneficial organisms. [source]
This is not medical advice. LizPlants is not a medical resource. Always consult a qualified healthcare professional before using plants medicinally.
Harvest Tips
Harvest when heads reach 8-10 inches tall and feel firm. For whole-head harvest, cut at soil level with a sharp knife in the early morning when leaves are crisp and cool. For continuous harvest, remove outer leaves as needed while leaving center for regrowth. Paris Island can produce a second, smaller harvest if left in the ground. Best harvested when morning temperatures are cool (before 10 AM). Store in refrigerator in breathable produce bags for up to 2 weeks.
Fun Facts
- 🌱 Paris Island Cos is named after the Greek island of Kos (Cos), where romaine lettuce is believed to have originated before spreading throughout the Mediterranean. The 'Paris Island' designation comes from seeds introduced to Paris markets in the 1800s.
- 🌱 This heirloom variety has been grown continuously since at least the early 1900s and remains virtually unchanged, making it a living piece of vegetable history prized by seed savers and heirloom gardeners worldwide.
- 🌱 Romaine lettuce is sometimes called 'cos lettuce' in British English, and Paris Island Cos is considered superior to modern hybrids by many chefs and gardeners for its exceptional flavor, often described as nutty and slightly sweet compared to iceberg varieties.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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