Romaine Lettuce

A tall, upright lettuce with sturdy, crisp leaves and a mild, slightly sweet flavor that is the classic choice for Caesar salads. Romaine is more heat-tolerant than many lettuce types and forms a loose, elongated head over time. Harvest outer leaves for extended picking or cut the full head at the base when it feels firm. Provide consistent moisture and light shade in summer to delay bolting and maintain crisp texture.

Sow seeds on the surface of moist seed-starting mix, pressing lightly but not covering (lettuce needs light to germinate). Seeds germinate in 4-10 days at 55-70°F. Temperatures above 80°F inhibit germination; refrigerate seeds for 24 hours before sowing in warm weather. Transplant when seedlings have 3-4 true leaves. For direct sowing, scatter seeds thinly and thin to 10-12 inches. Succession sow every 2-3 weeks for continuous harvest. Seeds remain viable for 3-5 years.

Start romaine lettuce seeds indoors 4-6 weeks before last frost, sowing on the soil surface or barely covered (seeds need light to germinate). Seeds germinate in 4-10 days at 55-70°F. Transplant hardened-off seedlings 10-12 inches apart in rows 12-18 inches apart. Direct sowing is also effective, scattering seeds thinly and thinning to proper spacing.

Romaine lettuce grows best in cool weather between 55-70°F but is more heat-tolerant than many lettuce types. Provide consistent moisture to maintain crisp leaf texture. In warm weather, provide afternoon shade with taller plants or shade cloth to delay bolting. Mulch around plants to keep roots cool and retain moisture. A light feeding with balanced fertilizer every 3-4 weeks supports steady growth.

Succession plant every 2-3 weeks from early spring through fall for continuous harvest. For the best quality heads, harvest in the morning when leaves are most turgid. Romaine can be grown as a cut-and-come-again crop by harvesting outer leaves, or left to form full heads over 55-70 days. In mild climates, romaine can be grown through the winter with minimal protection.

Romaine lettuce grows well with carrots, radishes, chives, and strawberries. Taller crops like tomatoes and corn provide beneficial afternoon shade in summer. Quick-growing radishes can be interplanted as row markers and harvested before lettuce needs the space. Avoid planting near celery, which may inhibit lettuce growth. Herbs like dill and cilantro attract beneficial predatory insects. Lettuce makes an excellent understory crop beneath trellised beans or peas.

Romaine lettuce thrives in fertile, well-drained soil with a pH of 6.0-7.0. Amend with compost before planting for moisture retention and fertility. Apply a balanced fertilizer at planting and side-dress lightly every 3-4 weeks. Avoid excessive nitrogen, which produces lush but bitter-tasting growth susceptible to disease. Lettuce has shallow roots, so consistent surface moisture is more important than deep watering. Organic mulch helps maintain the cool, moist conditions lettuce prefers.

Ideal Temperature

Hardiness Zone Compatibility

Harvest romaine lettuce as baby leaves starting at 25-30 days, or wait 55-70 days for full heads. For cut-and-come-again harvest, pick outer leaves when they reach 6-8 inches, leaving the inner growth to continue. For full heads, cut at the base when the head feels firm and upright. Harvest in the early morning for maximum crispness. If the center starts to elongate upward, the plant is beginning to bolt; harvest immediately as flavor turns bitter after bolting.

Storage & Preservation

Store whole heads or loose leaves in a plastic bag in the refrigerator crisper for 7-10 days. Romaine stores longer than most lettuce types due to its sturdy leaves. Wrap heads in damp paper towels for extended freshness. Lettuce does not freeze or dry well. For maximum shelf life, do not wash until ready to use. Romaine hearts (with outer leaves removed) keep particularly well. Revive slightly wilted leaves by soaking in ice water for 15-30 minutes.

Troubleshooting Common Problems

Bolting (premature flowering) is the main challenge, triggered by temperatures above 80°F, long days, or drought stress. Choose bolt-resistant varieties and provide afternoon shade in summer. Tip burn on inner leaves indicates calcium deficiency or erratic watering. Bitter flavor develops from heat stress or delayed harvest. Bottom rot occurs when leaves contact wet soil; use mulch as a barrier. Pale, leggy growth indicates insufficient light. Slugs are persistent pests in moist conditions.

Growing Tips

1. Lettuce seeds need light to germinate — never bury them. Press seeds gently onto moist soil surface or cover with the thinnest dusting of vermiculite. Germination rates drop dramatically when seeds are planted even 5mm deep.
2. Succession plant every 2-3 weeks from early spring through fall for a continuous romaine supply. A single planting produces one harvest; staggered sowing ensures you always have fresh lettuce coming in.
3. Romaine is more heat-tolerant than other lettuce types, but still bolts in sustained heat above 27°C (80°F). Extend your harvest by choosing bolt-resistant varieties like Jericho or Parris Island Cos for summer growing.
4. Provide afternoon shade in summer using shade cloth (40-50% shade rating), taller companion plants like tomatoes or corn, or by planting on the north side of trellised crops. Even 2-3 hours of shade delay bolting significantly.
5. Water consistently at soil level — overhead watering promotes leaf diseases and soil splash that causes bottom rot. Drip irrigation or soaker hoses are ideal. Romaine needs about 2.5cm (1 inch) of water per week.
6. Harvest outer leaves starting at 25-30 days for an extended cut-and-come-again harvest, or wait 55-70 days for full heads. Morning harvest produces the crispest, sweetest leaves because overnight sugars have not yet been consumed by daytime metabolism.
7. Interplant romaine with quick-maturing radishes as row markers and space-fillers. The radishes mature and are harvested in 25-30 days, just as the romaine needs more room to spread.
8. If your romaine tastes bitter, the most likely causes are heat stress, drought stress, or delayed harvest. Soak bitter leaves in ice water for 15-20 minutes to reduce bitterness before serving.