How to Grow Red Cos
Red Cos
Lactuca sativa var. longifolia
vegetableRed Cos, also known as Red Romaine, is a crisp leafy green with deep burgundy-red outer leaves and tender inner leaves. It offers a slightly bitter, nutty flavor and is prized for both nutrition and ornamental appeal in salads. This upright, elongated lettuce variety combines the crispness of romaine with attractive red pigmentation.
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Example Red Cos timeline · Pittsburgh, PA (Zone 6b)
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Plant Red Cos
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 Red Cos
Around Jun 16≈ 60 days after planting
Sample dates for Pittsburgh, PA. Sign up to get exact Red Cos dates for your own zip code.
Growing Conditions
Soil
Growing Zones
Find your zone →Thrives in zones 3-8; can be grown year-round with season selection in zones 9+
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Seedling
2-3 weeksTiny cotyledons emerge, first true leaves appear with reddish tinge
Keep soil moist but not waterlogged. Provide bright light. Thin crowded seedlings at 2-3 weeks.
Vegetative
3-4 weeksPlant develops 6-8 true leaves, forms rosette shape, red pigmentation intensifies
Maintain consistent moisture and even soil temperature. Apply thin layer of mulch. Begin light fertilizing every 2-3 weeks.
Heading
2-3 weeksLeaves tighten and elongate, forming characteristic cos/romaine shape with loose head
Continue regular watering and fertilizing. Monitor for bolting in warm weather; provide afternoon shade if temps exceed 75°F.
Maturity
1-2 weeks optimal harvest windowPlant reaches 10-14 inches tall, outer leaves deep red, inner leaves pale green and crisp
Continue consistent watering. Harvest outer leaves or whole head. Prevent bolting by harvesting promptly.
Bolting
Occurs when temps consistently exceed 75°F or after 80+ daysPlant sends up flowering stalk, leaves become bitter and tough
Harvest immediately or remove from garden. In cool seasons, this stage may be delayed.
Companion Planting
Plan your garden →Plant with:
Avoid planting near:
Common Pests
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Spray with water; use insecticidal soap or neem oil; encourage beneficial insects like ladybugs
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and
Hand-pick in early morning; use copper tape barriers; encourage ground beetles; apply food-grade diatomaceous earth
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Remove affected plants; rotate crops; use reflective mulch; practice crop rotation
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Use yellow sticky traps; spray with strong water; apply insecticidal soap; introduce parasitic wasps
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Improve air circulation; remove infected leaves; avoid overhead watering; use resistant varieties
Uses
Salads and fresh preparations
CulinaryRed Cos provides crisp texture, mild nutty flavor, and striking color for gourmet salads. Its sturdy leaves hold dressings well and are excellent for Caesar salads, composed salads, and raw vegetable platters. [source]
Cooking and braising
CulinaryUnlike delicate lettuces, Red Cos leaves withstand cooking. Lightly sauté or braise whole leaves as a side dish, adding them to soups, or wilting them into warm grain bowls. [source]
Nutritional and antioxidant benefits
MedicinalRed Cos is rich in vitamins A, C, and K, plus anthocyanins and polyphenols from its red pigmentation. These compounds support eye health, immunity, and may provide anti-inflammatory benefits. [source]
Garden ornament and visual interest
HouseholdThe deep red coloring makes Red Cos attractive in edible landscaping and containers. It adds visual contrast to herb gardens and vegetable beds while producing edible harvests. [source]
Beneficial pollinator habitat
WildlifeWhen allowed to bolt and flower, Red Cos produces small yellow flowers that attract bees and other pollinators. Bolted plants left in the garden support early-season pollinator populations. [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 outer leaves individually when 4-6 inches long for continuous production (cut-and-come-again method). For whole head harvest, cut at soil level in early morning when crisp. Red Cos is sweetest and most tender when harvested in cool weather. Harvest before bolting occurs; plants are typically ready 60-80 days from seed.
Fun Facts
- 🌱 Red Cos gets its color from anthocyanins, the same pigments found in blueberries and red wine, making it a phytonutrient powerhouse.
- 🌱 The word 'Cos' comes from the Greek island of Cos (Kos), where this lettuce variety was believed to originate thousands of years ago.
- 🌱 Red Cos leaves can change color intensity based on sun exposure—more sunlight intensifies the red pigmentation, while shade produces a more burgundy-green blend.
Gardening Terms
New to gardening? Learn about terms used in this guide:
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