Iceberg Lettuce in Zone 7B — Southeast

Iceberg lettuce might seem basic, but there's nothing quite like the crisp, refreshing crunch of a homegrown head, especially after working in the hot and humid Southeast garden. It's the perfect base for summer salads and adds a cool element to sandwiches, and harvesting your own is incredibly satisfying.

While our long summer and disease pressure can be challenging, careful timing and a few tricks will let you enjoy Iceberg lettuce from spring through fall. Our 235-day growing season gives you a great window to work with.

Starting Iceberg lettuce indoors gives you a head start, especially for a spring harvest. Begin in late January through mid February, about four weeks before you plan to transplant. This is particularly useful if you want to get a jump on the growing season before our moderate spring weather kicks in.

Use seed trays or small pots filled with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light—a grow light works best. Bottom watering helps prevent damping-off, a common issue with seedlings, especially with our humid air.

Transplant your Iceberg lettuce seedlings outdoors in early March through early April, once the danger of a hard freeze has passed. Before planting, harden them off for about a week by gradually exposing them to outdoor conditions. This acclimates them to the sun and wind, preventing transplant shock.

Space the plants about 12 inches apart in well-drained soil. Our spring weather can be unpredictable, so keep an eye on the forecast and be prepared to cover the seedlings if a late cold snap threatens.

Direct sowing Iceberg lettuce is another option, especially for a fall harvest. Sow seeds mid February through mid August, ensuring the soil temperature is consistently above 40°F. Prepare the soil by loosening it and adding compost.

Sow seeds about ¼ inch deep and keep the soil consistently moist. Thin the seedlings to about 12 inches apart once they emerge. Direct sowing is convenient, but you'll need to stay on top of weed control and ensure consistent moisture, especially during our hot summer months.

Consistent moisture is crucial for Iceberg lettuce, even more so than for other types of lettuce. Aim to keep the soil evenly moist but not waterlogged. The "finger test" works well – stick your finger about 2 inches into the soil; if it feels dry, it's time to water.

During the spring and fall, when temperatures are cooler, you'll likely need to water about 1 inch per week, depending on rainfall. In the heat of summer, especially with our afternoon thunderstorms, monitor the soil moisture closely. You might need to water more frequently, but avoid overwatering, which can lead to fungal diseases in our humid climate.

Water at the base of the plants to keep the leaves dry and reduce the risk of fungal issues. Overhead watering can be fine if done in the morning, allowing the leaves to dry out before nightfall. Mulching around the plants with straw or pine straw helps retain moisture and suppresses weeds, which is always a win in the Southeast. Signs of underwatering include wilting and stunted growth; overwatering can lead to yellowing leaves and root rot.

You can expect your first harvest of Iceberg lettuce in early May through mid November, about 70 days after planting. The key is to look for a firm, compact head that resembles the size you'd find at the grocery store. Iceberg is one of the more challenging lettuce types to grow, so patience is key.

To harvest, simply cut the head at the base with a sharp knife. This is a one-time harvest, as Iceberg lettuce doesn't typically produce additional heads.

As the first frost approaches in early November, harvest any remaining heads, even if they're not quite fully mature. They won't survive a hard freeze.

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, and sometimes on the outer leaves in severe cases.
• What causes it: A calcium uptake problem caused by inconsistent watering, similar to blossom end rot in tomatoes. High temperatures worsen the issue.
• How to fix/prevent it: Water consistently to maintain even soil moisture. Avoid fertilizers high in ammonium nitrogen. Ensure your soil has good calcium levels. Choose tip burn-resistant varieties. Provide shade during warm weather to keep the plants cooler.

Bolting in Heat

• What it looks like: The lettuce plant sends up a flower stalk. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: Extended warm temperatures above the crop's comfort zone. Lettuce bolts when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings to coincide with cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells. Mulch around the plants to keep the soil cool. Harvest the lettuce before bolting progresses too far.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may "farm" them for honeydew.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage ladybugs and lacewings, which are natural predators. Use insecticidal soap for heavy infestations. Neem oil also works well. Avoid excess nitrogen fertilizer, which attracts them.

Slugs

• What it looks like: Irregular holes in the leaves, especially on low-growing plants. Silvery slime trails on leaves and soil. Damage is worse at night and in wet weather.
• What causes it: 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 hiding spots like boards and debris. Water in the morning so the soil surface dries out by evening. Copper tape around beds can deter them. Diatomaceous earth around plants also helps.

Southeast Specific Challenges: Our hot and humid summers create a perfect environment for fungal diseases and pests. Consistent monitoring and preventative measures are key. The wet-summer rainfall can be a blessing and a curse, providing needed moisture but also increasing the risk of overwatering and disease.

Companion planting can help your Iceberg lettuce thrive. Carrots and radishes make great companions because they help break up the soil, improving drainage and aeration. Strawberries also work well, acting as a living mulch to keep the soil cool and moist. Chives and garlic deter pests like aphids and slugs with their strong scent.

Avoid planting celery and parsley near your lettuce. Celery competes for nutrients and water, while parsley can attract aphids, potentially spreading them to your lettuce.