Iceberg Lettuce in Zone 8B — Pacific Northwest

Iceberg lettuce might seem basic, but homegrown in the Pacific Northwest, it's a different story. The cool nights we get here actually improve the flavor, making it sweeter and crisper than anything you'll find at the store. Plus, the satisfaction of a perfect wedge salad with lettuce you grew yourself? Totally worth it.

We all know our springs can be a bit wet and our summers surprisingly dry, which can present some challenges. But with a 210-day growing season, you have plenty of time to get it right. Timing your planting and watering carefully will set you up for success.

Starting Iceberg lettuce indoors isn't essential, but it can give you a head start, especially if you're eager for an early crop. Start your seeds indoors from mid-February through early 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 windowsill or under grow lights.

Bottom watering is key to avoid damping off. Just set the tray in a shallow dish of water and let the soil soak it up from the bottom. Our springs here are slow to warm up, so indoor starting buys you some time.

Transplant your seedlings outdoors in late March through mid-April, once the soil has warmed up a bit. Before transplanting, harden them off for about a week by gradually exposing them to outdoor conditions. This prevents transplant shock.

Space them about 12 inches apart in a spot that gets full sun to partial shade. Even though it's spring, our overcast spring days can still stress young plants.

Direct sowing is a perfectly viable option for Iceberg lettuce here in the PNW. Sow seeds directly into the garden from early March through early August. You'll want to prepare the soil well, making sure it's loose and fertile.

Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to about 12 inches apart once they're a few inches tall. Direct sowing means you're more at the mercy of the weather, but it avoids transplant shock.

Consistent moisture is absolutely crucial for Iceberg lettuce, even more so than for loose-leaf varieties. It's not drought-tolerant at all. Aim to keep the soil consistently moist, but not waterlogged.

During our wet springs, you might not need to water much at all. But once the dry summer months hit, you'll need to water more regularly. A good rule of thumb is to check the soil about two inches down – if it feels dry, it's time to water. Give them about 1 inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid getting the leaves wet, which can encourage fungal diseases in our dry-summer humidity.

Signs of underwatering include wilting and stunted growth, while overwatering can lead to yellowing leaves and root rot. Applying a layer of mulch around your lettuce plants helps retain moisture and keep the soil cool, which is especially helpful during our mild summers.

You can expect your first harvest of Iceberg lettuce from mid-May through early 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 harvest. As the first frost approaches in early November, harvest any remaining heads, even if they're not quite fully mature. They won't improve much after a frost.

Here are some common problems you might encounter with Iceberg lettuce in the PNW:

Tip Burn

• What it looks like: Brown, dried edges on the inner lettuce leaves, sometimes spreading to the outer leaves.
• What causes it: Inconsistent watering leads to calcium uptake problems, worsened by warmer temperatures.
• How to fix/prevent it: Water consistently and deeply. Avoid fertilizers high in ammonium nitrogen. Make sure your soil has adequate calcium. Choose tip burn-resistant varieties and provide shade during hotter periods.

Bolting in Heat

• What it looks like: The lettuce plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: Extended warm temperatures trigger bolting, especially when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Select bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest promptly if bolting starts.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects thrive in warmer weather.
• How to fix/prevent it: Blast aphids off with a strong stream of water. Encourage natural predators like ladybugs and lacewings. Use insecticidal soap for heavy infestations, or neem oil systemically. 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 feed at night in moist conditions and hide during the day.
• How to fix/prevent it: Use beer traps (shallow dishes of beer sunk into the soil). Apply iron phosphate bait (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 or diatomaceous earth around plants.

Pacific Northwest Specific Challenges: Our mild summer heat usually isn't a huge problem for bolting if you time things right. However, slugs are a constant battle, especially with our wet springs. Watch out for late blight from nearby tomatoes, as it can sometimes affect lettuce too.

Companion planting can be a great way to improve your Iceberg lettuce crop in the PNW. Carrots are good companions because they deter lettuce root aphids. Radishes break up the soil, making it easier for lettuce roots to grow. Strawberries act as a living mulch, keeping the soil cool and moist. Chives and garlic are said to deter aphids and other pests.

Avoid planting lettuce near celery or parsley. Celery competes for the same nutrients and water, while parsley may attract aphids. By choosing the right companions, you can create a healthier and more productive garden.