Romaine Lettuce in Zone 5B — Great Plains

Romaine lettuce is a fantastic addition to any Great Plains garden. Its crisp texture and mild flavor elevate salads and sandwiches, plus it holds up well to grilling. There's real satisfaction in harvesting fresh greens from your backyard, especially when you know exactly what went into growing them – a welcome contrast to grocery store offerings.

Our region's extreme weather can be a challenge, but with careful timing, you can enjoy a steady supply of Romaine throughout much of our 178-day growing season. Knowing the risks of heat and hail, you can still get a good harvest.

Starting Romaine indoors gives you a jump start, but it's not always essential, especially if you're in the southern Plains where the growing season is a bit longer. If you choose to start indoors, aim for early to late March, about four weeks before you plan to transplant.

Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light – a sunny south-facing window or under grow lights. Bottom watering helps prevent damping off; set the tray in a shallow dish of water and let the soil absorb it. Remember, spring in the Plains is variable, so be prepared to adjust your schedule if we get an unexpected cold snap.

Transplant your Romaine seedlings outdoors from early April through early May, once the danger of hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings common in the Plains.

Plant them 8-10 inches apart in rows. Keep an eye on the forecast; a late frost can still happen, so have row covers or blankets ready to protect your young plants.

Direct sowing is a great option for Romaine lettuce, especially if you want successive harvests. Sow seeds from late March through late July, directly into well-prepared soil. Romaine prefers soil temperatures between 60°F and 70°F for optimal germination.

Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to 8-10 inches apart once they have a few true leaves. Direct sowing works well, but be mindful of potential hail or heavy rains that can damage young seedlings.

Consistent moisture is key to growing crisp, tender Romaine lettuce here in the Great Plains. Unlike leaf lettuce, Romaine tends to bolt faster in the heat. Our variable rainfall means you can't always rely on Mother Nature.

During the spring, check the soil moisture regularly using the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rain or irrigation. As the summer heat intensifies (and we know it does!), you may need to increase watering to prevent bolting.

Water at the base of the plants to avoid wetting the leaves, which can encourage disease in our low-to-moderate humidity. Signs of underwatering include wilting and stunted growth, while overwatering can lead to root rot. A layer of mulch, like straw or wood chips, helps retain soil moisture and regulate soil temperature, which is crucial in our extreme temperature swings.

You can expect your first Romaine lettuce harvest from late May through late October, depending on when you planted. Romaine is ready to harvest when the outer leaves are 6-8 inches long, or when the whole head feels firm and full-sized.

Cut the outer leaves with a clean knife, leaving the inner leaves to continue growing for a continuous harvest. Alternatively, you can harvest the entire head at once. It's crucial to harvest before the center stem starts to elongate, as this indicates bolting, which makes the leaves bitter.

As the first frost approaches in mid- October, harvest any remaining heads. You can also cover them with a blanket or row cover on frosty nights to extend the harvest a bit longer.

Here are some common problems you might encounter growing Romaine lettuce in the Great Plains:

Bolting in Heat

• What it looks like: A tall flower stalk emerges from the center of the lettuce head. The leaves become tough and bitter.
• What causes it: Extended periods of warm temperatures, especially when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest lettuce as soon as it's ready to prevent bolting.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on the stems and undersides of leaves. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations explode in warm weather.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage natural predators like ladybugs. Use insecticidal soap for heavy infestations. Avoid excessive nitrogen fertilizer.

Slugs

• What it looks like: Irregular holes in leaves, especially on lower leaves. Silvery slime trails on leaves and soil.
• What causes it: Night-feeding gastropods that thrive in moist conditions.
• How to fix/prevent it: Set out beer traps (shallow dishes of beer sunk into the soil). Use iron phosphate bait, which is pet-safe. Remove hiding spots like mulch and debris. Water in the morning so the soil surface dries out by evening.

Tip Burn

• What it looks like: Brown, dried edges on the inner lettuce leaves.
• What causes it: Calcium uptake problems caused by inconsistent watering, especially during hot weather.
• How to fix/prevent it: Water consistently. Ensure good soil calcium levels. Choose resistant varieties. Provide shade during warm weather.

Great Plains Specific Challenges: The hot, dry summers and variable rainfall in the Great Plains make consistent watering crucial for Romaine lettuce. The intense sun can also lead to bolting and tip burn, so providing shade during the hottest part of the day is beneficial. Wind protection is essential to prevent leaf damage and drying out.

Companion planting can help your Romaine lettuce thrive in the Great Plains. Carrots are good companions because they deter lettuce root aphids. Radishes break up the soil and act as a trap crop for flea beetles. Strawberries provide ground cover and help retain moisture. Chives and onions deter aphids and other pests with their strong scent.

Avoid planting Romaine lettuce near celery or parsley. Celery competes for nutrients, and parsley can attract swallowtail butterflies, whose caterpillars may munch on your lettuce.