Growing Lettuce Year-Round: Soil, Hydro, and Container Methods for Sweet, Crisp Leaves

Why Lettuce is the Perfect Beginner Crop

Lettuce germinates in three days, matures in as little as three weeks for baby leaves, and asks for nothing more than cool air, bright diffused light, consistent moisture, and loose, fertile soil. A single 4 × 8 foot bed or a 20-liter tote under LED bars can supply a family salad bowl every day of the year once you grasp two principles: variety selection matched to the season and nonstop succession sowing.

This guide walks you through both principles, with exact seed lists, step-by-step indoor and outdoor setups, and—crucially—how to keep slugs, aphids, and summer bolting at bay without toxic sprays.

Lettuce Varieties Decoded

Butterhead (Bibb, Boston)

Tender, mild, loose heads that slip neatly into a sandwich. Great for cool tunnels or indoor hydro systems where space is tight and airflow is high.

Romaine (Cos, Little Gem)

Crisp ribs and sweet hearts. Heat-tolerant varieties such as ‘Rouxai’ and ‘Parris Island Cos’ resist tip burn under LEDs and push into early summer without bolting.

Loose-leaf (Red Sails, Oakleaf)

Continuous cut-and-come-again production. Harvest outer leaves at baby stage in 21–25 days and leave the crown for five harvests.

Iceberg/Crisphead

Classic tight heads. Needs the longest cool period—plant only in fall for overwintering under row covers in USDA zone ≥7.

Summer Crisp/Batavian

Heat-defying, ruffled varieties like ‘Muir’ and ‘Sierra’ keep sweet above 24 °C. This is the missing link between spring and late-summer crops.

Growing Lettuce Outdoors

Soil & Bed Layout

• pH 6.0–7.0. Work in 2 inches of compost plus 3 cups balanced organic fertilizer per 100 sq ft.
• Loosen soil to 8 inches deep—lettuce roots are shallow but quickly pout in caked soil.
• Light shade cloth (30 %) or a northern fence keeps July soil temperature below 20 °C, dodging premature bolting.

Direct Seeding Calendar (Temperate Zones)

Pelleted Seed for Precision Spacing

Use pelleted seed for direct sowing: 1 inch apart in rows 8 inches wide, then thin to every 6 inches for full heads or cut baby leaf strips at 2–3 inches high.

Succession Planting Formula

To never be without lettuce, sow 15 percent of your total space every week. A family of four eats roughly 24 heads or 250 grams of baby leaf mix per week. Sow 3 grams (¼ teaspoon) loose-leaf seed or 24 pelleted romaine seeds weekly in plug trays or bare soil modules.

Lettuce in Containers

Best Pots & Soil Mix

• Window box (4 inch deep) for cut-and-come-again leaf crops.
• 3-gallon fabric pots for single heads.
• Loamy potting mix with 30 % coconut coir and a dash of biochar retains water yet drains excess.

Keep containers in morning sun, afternoon shade on south-facing balconies. Lift them off the deck with bricks to reduce radiated heat.

Indoor Lettuce Under LEDs

Basic Hardware

• 4-foot LED shop light (2200 lm, 40 W, 6500 K) hung 12 inches above trays.
• NFT (nutrient film technique) channels or the classic Kratky mason-jar method.
• 20-gallon reservoir with air pump in summer—roots stay cool and oxygenated.

Hydroponic Nutrient Recipe

EC 1.2 mS cm⁻¹, pH 5.8–6.2. Commercial three-part “Lettuce” formulas work; purists dissolve Masterblend 4-18-38, calcium nitrate, and magnesium sulfate in a 1 : 1 : 0.5 ratio.

Plug & Play Harvest Calendar

• Day 0: Pre-soak seed 30 min, sow 1 seed per 1-inch rockwool plug.
• Day 3: Sprout under transparent domes, open vents.
• Day 14: Transplant plugs into 2-inch net cups.
• Day 35: First baby-leaf cut (loose-leaf).
• Day 42–50: single romaine heads.

Trouble-Shooting Lettuce Problems

Bolting (Flowering)

Cause: Night temps >15 °C or long days above 14 hrs. Fix: choose bolt-resistant varieties, plant below 30 % shade cloth, harvest promptly.

Tip Burn

Cause: Rapid transpiration and calcium not keeping pace. Fix: increase humidity, lessen LED heat, maintain steady solution strength.

Aphids

Fix: Release 1500 green lacewing larvae per 100 square feet, or blast leaves with water hose every second morning.

Slug & Snail Damage

Fix: Copper tape around container rims, board trap nightly, and sole source of moisture 3” deep beer saucers in beds.

Pro Tips for Restaurant-Quality Leaves

• Harvest pre-dawn or after watering—cells are turgid, sugars highest.
• Ice dunk immediately: 30 seconds in icy water snaps out field heat and crispifies ribs.
• Store leaves in a produce saver half-filled with air; do not pack tight.

Reading the Transplant Leaves

Dark, leathery surface under LEDs means light is too close—raise lamps 2 inches. Pale, weak stems hint at too little light—drop lamps or replace with a stronger bar. Purple-tinted veins often follow low nighttime temperatures; seedlings bounce back in 48 hrs once temps rise.

Seed Saving & Genetic Vigil

If a mysterious prized romaine starts to bolt in midsummer, stake the stem and let it self-pollinate in a vacant corner. Lettuce is 90 % self-pollinating, so save seed from 5–7 heads for genetic breadth; dry seeds in paper bags, then refrigerate in glass jars for up to 5 years.

12-Month Lettuce Planner

Glossary of Terms

Cut-and-Come-Again

Repeated harvest of outer leaves, leaving the crown intact.

Tip Burn

Brown necrosis of leaf margins caused by calcium or water stress.

Hydroponic EC

Electrical conductivity measuring dissolved salts; lettuce likes 1.0–1.3 mS cm⁻¹.

Final Resource List

• Cornell University Controlled Environment Agriculture (CEA) Hydroponic Lettuce Guide – cuaes.cornell.edu
• ATTRA Lettuce Production Field Guide – attra.ncat.org
• Johnny’s Seeds Lettuce Variety Comparison Chart – johnnyseeds.com

Disclaimer: This article was generated with the assistance of an AI language model as a journalistic overview. Always cross-reference local extension bulletins for variety trials and disease patterns specific to your region.