Romaine Lettuce in Zone 7B — Southeast

Romaine lettuce is a fantastic addition to any Southeast garden. Its crisp texture and slightly bitter flavor make it perfect for salads, wraps, and even grilling. Plus, there's nothing quite like the satisfaction of harvesting your own fresh greens when the grocery store options are looking a little sad after a long, hot summer.

Our long growing season in Zone 7B means you can enjoy Romaine lettuce for a good portion of the year. While we definitely have to deal with our share of heat and humidity, careful timing and smart gardening practices will help you beat the worst of it and keep your lettuce patch thriving for much of our 235-day season.

Starting Romaine lettuce indoors in the Southeast is certainly an option, especially for getting a jump start on the spring crop. Sow your seeds indoors from late January through mid February, about four weeks before you plan to transplant them outdoors.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist by bottom watering, and provide plenty of light, either from a sunny window or a grow light. Given our moderate springs, starting indoors gives you a little more control over the environment, particularly if we get a late cold snap.

Transplant your Romaine lettuce seedlings outdoors in early March through early April, once the threat of a hard freeze has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space the plants 8-10 inches apart in well-drained soil. Keep an eye on the weather forecast, as we can still get some chilly nights during this time. If a frost is predicted, cover your young plants with row covers or blankets to protect them.

Direct sowing Romaine lettuce is a great option, especially for succession planting throughout the growing season. You can direct sow from mid February through late August, staggering your plantings every few weeks to ensure a continuous harvest.

Prepare your soil by loosening it and adding compost. Sow the seeds about ¼ inch deep and keep the soil consistently moist until they germinate. Thin the seedlings to 8-10 inches apart once they have a few true leaves. Direct sowing is a simple method, but be mindful of the soil temperature. Lettuce seeds germinate best when the soil is between 60-70°F.

Watering Romaine lettuce properly is crucial in the Southeast's hot, humid climate. Consistent moisture is key to crisp, tender leaves. Inconsistent watering can lead to bolting, which makes the leaves bitter.

During the spring and fall, when temperatures are milder, aim to water deeply about once a week, providing about 1 inch of water. In the heat of summer, you may need to water every other day, or even daily during dry spells. Use the finger test – if the top 2 inches of soil feel 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 environment. Signs of underwatering include wilting leaves, while overwatering can lead to root rot. A layer of mulch around your plants will help retain moisture and keep the soil cool.

You can expect your first harvest of Romaine lettuce from late April through mid November, depending on when you planted. Romaine is typically ready to harvest about 65 days after planting.

Harvest individual outer leaves when they are 6-8 inches long, or harvest the entire head when it's firm and full-sized. Cut the head at the base, leaving the root intact if you want it to potentially regrow. To encourage continued production, harvest outer leaves regularly, allowing the inner leaves to mature.

As the first frost approaches in early November, harvest any remaining mature heads. You can also cover your plants with row covers to extend the harvest a bit longer, protecting them from light frosts.

Here are some common problems you might encounter growing 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 bitter and tough.
• What causes it: Extended periods of warm temperatures, especially when days consistently exceed 80°F. Romaine is a cool-season crop, and our long summers can trigger bolting.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during the hottest part of the day using shade cloth. Mulch to keep the soil cool. Harvest your lettuce before bolting progresses.

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: Rapid-reproducing sap-sucking insects that thrive in warm weather.
• How to fix/prevent it: Knock aphids off with a strong spray of water. Encourage natural predators like ladybugs and lacewings. Use insecticidal soap for heavy infestations. Neem oil can also be effective. Avoid over-fertilizing with nitrogen.

Slugs

• What it looks like: Irregular holes in leaves, especially on lower leaves. Silvery slime trails on leaves and soil.
• What causes it: Slugs are gastropods that feed at night in moist conditions. They love our humid climate.
• 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 debris. Water in the morning so the soil surface dries out by evening. Copper tape around beds can deter slugs. Diatomaceous earth around plants is also effective.

Tip Burn

• What it looks like: Brown, dried edges on the inner lettuce leaves. Can affect outer leaves in severe cases.
• What causes it: Calcium uptake problems caused by inconsistent watering and high temperatures.
• How to fix/prevent it: Water consistently to ensure even moisture. Avoid fertilizers high in ammonium nitrogen. Ensure good soil calcium levels. Choose resistant varieties. Provide shade during warm spells.

Southeast Specific Challenges: The combination of hot heat, humid humidity, and wet-summer rainfall in the Southeast creates a perfect environment for fungal diseases and pests. Consistent monitoring and proactive measures are essential for keeping your Romaine lettuce healthy and productive. Make sure you give your plants space for air to circulate and scout for pests regularly.

Companion planting can be a great way to improve the health and productivity of your Romaine lettuce in the Southeast.

Good companions include:

• Carrots: Carrots deter lettuce root aphids and don't compete for the same nutrients.
• Radishes: Radishes are fast-growing and help break up the soil, making it easier for lettuce roots to penetrate. Plus, they can act as a trap crop for flea beetles.
• Strawberries: Strawberries provide ground cover, helping to retain moisture and suppress weeds around your lettuce.
• Chives & 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 and water.
• Parsley: Parsley attracts swallowtail butterflies, whose caterpillars can munch on your lettuce leaves.