Romaine Lettuce in Zone 6B — Southeast

Romaine lettuce is a fantastic addition to any Southeast garden. Its crisp texture and mild flavor make it a versatile choice for salads, wraps, and even grilling. Plus, there's nothing quite like the satisfaction of harvesting your own fresh lettuce, especially when the summer heat starts to kick in.

While our hot and humid summers here in Zone 6B can present some challenges, the long growing season gives you plenty of opportunities to enjoy homegrown Romaine. By timing your plantings right, you can harvest delicious lettuce from mid-spring all the way into fall, taking full advantage of our 208-day growing season.

Starting Romaine lettuce indoors can give you a head start, especially for an early spring harvest. Begin sowing seeds indoors from mid-February through early March, about four weeks before you plan to transplant them outside. Use seed trays or small pots filled with a good seed-starting mix.

Keep the trays in a warm location, around 65-70°F, and provide plenty of light, either from a sunny window or a grow light. Bottom watering is especially helpful to prevent damping off; set the tray in a shallow container of water and let the soil absorb moisture from the bottom. Given our moderate spring, starting indoors buys you some time against any lingering cool snaps.

Transplant your Romaine lettuce seedlings outdoors from late March through mid-April, 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 sunlight and temperature changes.

Choose a spot with full sun to partial shade and space the plants 8-10 inches apart. Be sure to keep an eye on the weather forecast; those unexpected late-season freezes can still sneak in. Cover your young plants with a frost blanket if temperatures are predicted to drop.

Direct sowing Romaine lettuce is a convenient option, especially for succession planting throughout the growing season. Sow seeds directly into the garden from early March through mid-August. Prepare the soil by loosening it and adding compost or other organic matter.

Lettuce seeds germinate best in cool soil, so aim for soil temperatures between 60-70°F. Sow seeds about ¼ inch deep and space them 8-10 inches apart. Thin seedlings as needed to ensure proper spacing. Direct sowing works great, but keep in mind that you'll need to stay on top of weed control, especially in our fertile Southeast soil.

Romaine lettuce needs consistent moisture to produce crisp, tender leaves, but our wet-summer climate can make watering a bit tricky. Aim to provide about 1 inch of water per week, either through rainfall or irrigation. The "finger test" is a good way to check soil moisture: stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water.

Water at the base of the plants to avoid wetting the leaves, which can increase the risk of fungal diseases in our humid climate. Overhead watering is fine occasionally, but try to do it in the morning so the leaves have time to dry before nightfall. Signs of underwatering include wilting leaves and slow growth. Overwatering, on the other hand, can lead to root rot and yellowing leaves.

A layer of mulch around your lettuce plants can help retain soil moisture and suppress weeds. Pine straw or shredded leaves work well in our region.

You can expect your first harvest of Romaine lettuce from mid-May through early November, depending on when you planted. Romaine is usually ready to harvest about 65 days after planting. Look for outer leaves that are 6-8 inches long, or harvest the whole head when it feels firm and full-sized.

To harvest individual leaves, simply cut them off near the base of the plant, leaving the inner leaves to continue growing. For a whole head harvest, cut the plant off at the base. To encourage continued production, remove any yellowing or damaged leaves.

As our first frost approaches in late October, consider covering your lettuce plants with a frost blanket to extend the harvest a bit longer. You might even be able to sneak in a few more salads before winter truly sets in.

Here are some common problems you might encounter with Romaine lettuce in the Southeast:

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: Romaine is a cool-season crop, and it bolts (goes to seed) when temperatures rise consistently above 80°F. This is a common problem during our long summer.
• How to fix/prevent it: Time your plantings for cooler weather (spring and fall). Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest lettuce promptly before it bolts.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that thrive in warm weather. Populations can explode quickly.
• How to fix/prevent it: Spray plants with a strong stream of water to knock aphids off. Encourage natural predators like ladybugs and lacewings. Apply insecticidal soap for heavy infestations. Neem oil can also be effective.

Slugs

• What it looks like: Irregular holes in leaves, especially on low-growing plants. Silvery slime trails on leaves and soil.
• What causes it: Slugs are nocturnal pests that feed on lettuce leaves in moist conditions. They hide under mulch and debris during the day.
• How to fix/prevent it: Use beer traps (shallow dishes of beer sunk into the soil). Apply iron phosphate bait (which is pet-safe). Remove hiding spots like mulch and boards. Water in the morning so the soil surface dries out by evening.

Tip Burn

• What it looks like: Brown, dried edges on inner lettuce leaves. Can affect outer leaves in severe cases.
• What causes it: Tip burn is caused by a calcium uptake problem, often due to inconsistent watering or high temperatures.
• How to fix/prevent it: Water consistently. Avoid fertilizers high in ammonium nitrogen. Ensure good soil calcium levels. Choose resistant varieties. Provide shade during warm weather.

Southeast Specific Challenges: Our hot, humid climate and wet-summer rainfall can exacerbate these problems. High humidity promotes fungal diseases, so good air circulation is essential. Regular rainfall can also create ideal conditions for slugs. And those summer heat waves can quickly cause lettuce to bolt. Be vigilant, and adapt your gardening practices to our unique regional conditions.

Companion planting can be a helpful strategy for growing Romaine lettuce in the Southeast.

Good companions include:

• Carrots: Carrots deter lettuce aphids and loosen the soil.
• Radishes: Radishes are fast-growing and help deter flea beetles. They also break up the soil, making it easier for lettuce roots to grow.
• Strawberries: Strawberries act as a living mulch, helping to keep the soil cool and moist.
• Chives and Onions: These alliums deter aphids and other pests with their strong scent.

Avoid planting Romaine lettuce near:

• Celery: Celery and lettuce compete for the same nutrients in the soil.
• Parsley: Parsley can attract aphids, which can then spread to your lettuce.