Iceberg Lettuce in Zone 7A — Southeast

Iceberg lettuce might seem basic, but a crisp, homegrown head, fresh from your garden, is a different experience than what you find at the grocery store. It's surprisingly versatile, perfect for adding a cool crunch to sandwiches or salads, especially welcome during our long, hot summers. There's a simple satisfaction in growing your own, and Iceberg's tight head makes it less prone to slug damage than some other leafier types.

We definitely have our challenges here in the Southeast, like humidity and pests. But with careful timing and a little extra attention, you can absolutely grow beautiful heads of Iceberg lettuce. Our long growing season, nearly 225 days, gives you a great window of opportunity for both spring and fall crops.

Starting Iceberg lettuce indoors gives you a head start, but it's not strictly necessary in our climate. It's most useful if you want an extra-early spring crop.

If you're starting indoors, sow seeds early to late February, about four weeks before you plan to transplant. Use seed trays with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light, either from a grow light or a very sunny window. Bottom watering helps prevent damping off, so set the tray in a shallow dish of water and let the soil soak it up. Our moderate spring gives you a decent amount of time to get those seedlings going before the real heat hits.

Transplant your Iceberg lettuce seedlings outdoors mid March through early April. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a spot with full sun to partial shade, and space the plants about 12 inches apart. Be mindful of late-season frosts, which can still occur in early spring. Cover the transplants if a frost is predicted. A cloudy day is best for transplanting, to avoid shocking the young plants.

Direct sowing is a great option for Iceberg lettuce in the Southeast, especially for a fall crop. You can direct sow late February through mid August.

Prepare the soil by loosening it and adding compost. Lettuce seeds need light to germinate, so sow them shallowly, about 1/4 inch deep. Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to 12 inches apart once they have a few true leaves. Direct sowing works best when the soil temperature is between 60°F and 70°F.

Consistent watering is absolutely critical for Iceberg lettuce in our hot, humid Southeast climate. More so than other lettuce types, Iceberg needs even moisture to form a tight head and prevent tip burn.

During the spring and fall, when temperatures are cooler, aim for about 1 inch of water per week, either from rain or irrigation. In the heat of summer, you might need to increase that to 1.5-2 inches per week. Use the "finger test" – stick your finger about 2 inches 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 encourage fungal diseases in our humid environment.

Signs of underwatering include wilting and stunted growth. Overwatering can lead to root rot, so make sure the soil is well-draining. Yellowing leaves can also be a sign of overwatering. A layer of mulch, like pine straw or shredded leaves, can help retain moisture and keep the soil cool.

You can expect your first harvest of Iceberg lettuce early May through mid November, about 70 days after planting. The key is to look for a firm, compact head that feels similar to what you'd find at the grocery store.

To harvest, simply cut the head at the base with a sharp knife. Unlike some other lettuce types, Iceberg doesn't offer continuous harvests. You get one head per plant. As the first frost approaches in early November, harvest any remaining heads, even if they're not quite fully mature. They will not improve after a frost.

Here are some common problems you might encounter growing Iceberg lettuce in the Southeast:

Tip Burn

• What it looks like: Brown, dried edges on the inner lettuce leaves. It can spread to the outer leaves in severe cases.
• What causes it: A calcium uptake problem caused by inconsistent watering, worsened by our high summer temperatures. It's similar to blossom end rot in tomatoes.
• How to fix/prevent it: Water consistently! Avoid fertilizers high in ammonium nitrogen. Make sure your soil has adequate calcium levels. Provide shade during the hottest part of the day. Choose tip-burn-resistant varieties.

Bolting in Heat

• What it looks like: The lettuce plant sends up a flower stalk. The leaves become tough and bitter.
• What causes it: Extended warm temperatures. Lettuce bolts when days consistently exceed 80°F. We all know how often that happens here!
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep the soil cool. Harvest the lettuce before bolting progresses too far.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on the stems and undersides of leaves. You might also see a sticky honeydew residue or curled, distorted new growth.
• What causes it: These sap-sucking insects reproduce rapidly, especially in warm weather. Ant colonies may even "farm" them for their honeydew.
• How to fix/prevent it: A strong spray of water will knock them off. Encourage ladybugs and lacewings, which are natural predators. Use insecticidal soap for heavy infestations or neem oil. Avoid excess nitrogen fertilizer, which attracts them.

Slugs

• What it looks like: Irregular holes in the leaves, especially on low-growing plants. You'll also see silvery slime trails on the leaves and soil. The damage is worse at night and in wet weather.
• What causes it: Slugs are gastropods that feed at night in moist conditions. They hide under mulch, boards, and debris during the day.
• How to fix/prevent it: Use beer traps (shallow dishes of beer sunk into the soil). Iron phosphate bait is pet-safe. Remove any hiding spots. Water in the morning so the soil surface dries out by evening. Copper tape around beds and diatomaceous earth around plants can also help.

Southeast Specific Challenges: Our hot, humid summers and wet-summer rainfall mean that fungal diseases are a constant threat to lettuce. Good air circulation and careful watering practices are essential. Japanese beetles can also be a nuisance, skeletonizing the leaves. Row covers can help protect your plants from both pests and excessive sun.

Companion planting can help your Iceberg lettuce thrive. Carrots are good companions because they deter lettuce root aphids. Radishes also deter pests and break up the soil, making it easier for lettuce roots to grow. Strawberries provide ground cover, keeping the soil cool and moist. Chives and garlic are natural pest repellents.

Avoid planting Iceberg lettuce near celery and parsley. Celery attracts aphids, which can then spread to your lettuce. Parsley can inhibit lettuce growth.