Grower’s Reference Guide: Lettuce

Introduction

Lettuce (Lactuca sativa) is a versatile, cool-season leafy green that thrives in organic gardens and small farms. It is a staple in salads and sandwiches and is grown worldwide for its crisp texture and mild flavor. Organic lettuce cultivation enhances its nutritional value, avoids synthetic chemicals, and supports soil health.

Fun Fact:

Lettuce was first cultivated by the ancient Egyptians over 6,000 years ago and was considered a sacred plant dedicated to the god Min!

Scientific Information

• Scientific Name: Lactuca sativa
• Key Characteristics: Fast-growing, cool-weather crop with tender, edible leaves that come in a variety of shapes, textures, and colors.
• Common Uses: Salads, wraps, sandwiches, juicing, garnishes, and companion planting for pest control.

Growth Overview

• Annual or Perennial? Annual
• Growth Form: Loose-leaf, head-forming, or romaine-type
• Toxicity: Non-toxic to humans and animals
• Edibility: Fully edible
• Size & Growth Rate: Grows 6–12 inches tall; matures in 30–70 days depending on variety

Varieties of Lettuce & Related Greens

Loose-Leaf Lettuce Varieties:

• Green Leaf Lettuce – Classic, tender, mild-flavored leaves.
• Oakleaf Green Lettuce – Delicate, lobed leaves with a buttery taste.
• Royal Oakleaf Lettuce – Larger, darker green version with crisp leaves.
• Prizehead Lettuce – Loose, frilly, red-tinted green leaves.

Head-Forming Lettuce Varieties:

• Buttercrunch Lettuce – Soft, buttery leaves with a mild flavor.
• Bibb Lettuce – Small, compact, and tender leaves.
• Iceberg Lettuce – Crisp, round heads with a refreshing crunch.
• Cimarron Red Lettuce – Romaine-style, deep red leaves with a robust taste.

Romaine Lettuce Varieties:

• Romaine Lettuce – Long, upright leaves with a crisp texture.

Specialty & Related Greens:

• Arugula Seeds – Peppery, slightly spicy green for salads.
• Spinach Seeds – Nutrient-rich, tender leafy green.
• Swiss Chard Seeds – Colorful stalks and thick, flavorful leaves.
• Kale Seeds – Hardy, nutritious, and cold-resistant leafy green.
• Mache Seeds – Small, nutty-flavored leaves.
• Sorrel Seeds – Tart, lemony leaves, great for soups and salads.
• Curled Mustard Seeds – Spicy, frilled mustard greens.
• Curled Cress Seeds – Sharp, peppery greens, similar to watercress.
• Broadleaf Endive Seeds – Bitter, crisp, large leaves.
• Curled Ruffec Endive Seeds – Frilly, slightly bitter green.
• Mizuna Seeds – Japanese mustard green with a mild, peppery flavor.
• Collards Seeds – Thick, nutrient-dense, cold-hardy greens.
• Radicchio Seeds – Bitter, red-leafed Italian chicory.

Growing Conditions

Ecosystem/Climate

Lettuce thrives in cool-season climates (spring and fall) with mild temperatures between 45°F–75°F (7°C–24°C). It can tolerate light frost but bolts in excessive heat.

Soil & pH

• Prefers well-draining, nutrient-rich soil.
• Optimal pH range: 6.0–6.8.
• Improve soil with compost, aged manure, and worm castings.

Temperature & Hardiness

• Ideal range: 45°F–75°F.
• Hardiness zones: 3–9 (cool-season crop).

Moisture & Humidity

• Requires consistent, even moisture (1 inch per week).
• Use mulch to retain soil moisture and regulate temperature.

Season

• Spring & Fall: Best growing seasons.
• Summer: Grow heat-resistant varieties like romaine and oakleaf in partial shade.

Companion Plants

• Good Companions: Carrots, radishes, onions, chives, dill, marigolds (pest deterrent).
• Avoid: Cabbage, broccoli (competes for nutrients).

Pollination

Lettuce is self-pollinating and doesn’t require pollinators.

Propagation & Seed Starting

Growing from Seed

• Seed Selection: Choose organic, non-GMO seeds.
• Harvesting Seeds: Allow some plants to bolt; collect seeds once flower heads dry.
• Germination:
  • Ideal temperature: 50°F–65°F.
  • Days to germinate: 7–14 days.
  • Tip: Refrigerate seeds before planting for better germination in warm climates.

Propagation

• Best grown directly from seed.

Transplanting

• Start indoors 4 weeks before last frost, then transplant once true leaves form.

Cultivation & Maintenance

Organic Fertilizers

• Best options: Compost tea, fish emulsion, aged manure.
• Schedule: Feed every 2 weeks during growth.

Mulching

• Use straw or grass clippings to keep soil cool and moist.

Pruning/Training

• Cut outer leaves regularly to encourage new growth.
• Thin plants 4–6 inches apart to prevent overcrowding.

Seasonal Care

• Summer: Provide shade cloth to prevent bolting.
• Winter: Use cold frames or row covers for protection.

Pests & Diseases

Common Diseases

• Downy mildew: Prevent with good air circulation.
• Leaf spot: Avoid overhead watering.
• Damping off: Ensure well-draining soil.

Pest Management

• Aphids, slugs, cutworms: Control with neem oil, hand-picking, and natural predators like ladybugs.
• Floating row covers prevent insect infestations.

Harvesting

When & How

• Loose-leaf types: Cut outer leaves when they reach 4 inches.
• Head-forming types: Harvest whole heads when firm and mature.
• Bolting signs: Leaves turn bitter—harvest before flowering.

Storage & Preservation

How to Store

• Store fresh lettuce in a damp cloth in the fridge for up to 10 days.
• Keep in a ventilated container to prevent wilting.

How to Preserve

• Freezing not recommended—lettuce loses texture.
• Best method: Store seeds for future planting.

Seed Saving

• Dry and store in an airtight container in a cool, dark place.

Usage & Nutrition Information

Edibility

• Fully edible—leaves used fresh, in wraps, or juiced.

Culinary Uses

• Salads, sandwiches, wraps, garnishes, soups (for some varieties like romaine).

Nutritional Information

• Low-calorie (5–15 calories per cup).
• Rich in:
  • Vitamin A (eye health).
  • Vitamin K (bone health).
  • Folate (cell growth).

Pet Safety

• Safe for dogs, cats, rabbits, and guinea pigs.

Troubleshooting

• Bitter leaves? Too much heat—harvest sooner.
• Bolting? Provide shade & mulch to keep roots cool.
• Slow growth? Boost nitrogen with organic fertilizer.

Final Thoughts

Lettuce is one of the easiest and most rewarding crops for organic growers. With the right care, you can enjoy a steady supply of fresh, homegrown greens all season long! 🌱🥬