Romaine Lettuce in Zone 7A — Pacific Northwest

Romaine lettuce is a fantastic addition to any Pacific Northwest garden. Its crisp texture and mild flavor shine in salads, sandwiches, and even grilled preparations. The cool nights of our mild summers actually *improve* the flavor, making it sweeter and less bitter than what you find in the store. Plus, there's nothing like the satisfaction of harvesting your own fresh greens right from your backyard.

While we enjoy relatively mild summers, our springs can be slow to warm up, and we sometimes struggle to get enough heat for truly warm-season crops. Luckily, Romaine thrives in cooler weather, and with a little planning, you can enjoy a long harvest window within our 183-day growing season.

Starting Romaine indoors gives you a head start, especially with our often cool, overcast spring days. You can sow seeds indoors from early to late March, about four weeks before you plan to transplant them outside. Use seed trays or small pots filled with a good seed-starting mix, and keep them in a warm spot, ideally around 70°F, until germination.

A heat mat can help speed things up, but isn't essential. Make sure your seedlings get plenty of light – a grow light is ideal, as our natural light can be weak in early spring. Water gently from the bottom to avoid damping off; set the tray in a shallow dish of water and let the soil absorb it.

Transplant your Romaine seedlings outdoors from early April through early May, once the soil has warmed up a bit and the risk of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Start with a few hours of shade, then gradually increase the sun exposure each day.

Space your Romaine plants 8-10 inches apart in well-drained soil. Keep an eye on the weather forecast – those late-season cold snaps can still happen. Be ready to cover your seedlings with row covers or cloches if frost threatens.

Direct sowing Romaine is a simple and effective method, especially if you're looking for a continuous harvest. Sow seeds directly into the garden from late March through early August. The key is to ensure the soil is consistently moist and has warmed up a bit; aim for a soil temperature around 60°F.

Prepare the soil by loosening it and adding some compost or well-rotted manure. Sow seeds about ¼ inch deep and 8-10 inches apart. Thin seedlings as they grow, leaving the strongest plants to mature. Direct sowing is great for succession planting, allowing you to harvest fresh lettuce throughout the growing season.

Romaine lettuce needs consistent moisture to produce crisp, tender leaves. In our Pacific Northwest climate, that means paying close attention to the weather and adjusting your watering schedule accordingly. While our summers are mild, they can also be quite dry, so consistent watering is key.

During the wet springs, you might not need to water at all, but once the dry summer months arrive, check the soil regularly. The "finger test" is a good guide: stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our sometimes humid conditions. Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to root rot, indicated by yellowing leaves and a generally unhealthy appearance. A layer of mulch, like straw or compost, will help retain moisture and keep the soil cool during our mild summer months.

You can expect your first Romaine harvest from late May through late October, depending on when you planted. Romaine is 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 snap or cut them off near the base of the plant, leaving the inner leaves to continue growing. For a whole head harvest, cut the stem at the base of the plant. To encourage continued production, avoid damaging the central stem.

As our first frost approaches in mid- October, harvest any remaining mature heads. Even though Romaine is semi-hardy, a hard frost can damage the leaves. You can also cover plants with row covers to extend the harvest a bit longer into the fall.

Here are some common problems you might encounter growing Romaine lettuce in the Pacific Northwest:

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: Extended warm temperatures. Even though we have mild summers, a few days above 80°F can trigger bolting, especially in susceptible varieties.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade with row covers or shade cloth during warm spells. Mulch to keep the soil cool. Harvest lettuce before bolting progresses too far.

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. Aphids thrive in warm weather.
• How to fix/prevent it: A strong spray of water from the hose can knock them off. Encourage beneficial insects like ladybugs and lacewings. Use insecticidal soap for heavy infestations. 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: These gastropods love our moist conditions, especially in spring and fall.
• How to fix/prevent it: Use beer traps (shallow dishes of beer sunk into the soil). Apply iron phosphate bait (it's pet-safe). Remove hiding spots like weeds and debris. Water in the morning so the soil surface dries out by evening. Copper tape around beds can also deter slugs. Diatomaceous earth can be effective if reapplied after rain.

Tip Burn

• What it looks like: Brown, dried edges on the inner lettuce leaves.
• What causes it: Calcium uptake issues due to inconsistent watering. Can be worsened by high temperatures.
• How to fix/prevent it: Water consistently. Avoid fertilizers high in ammonium nitrogen. Ensure good soil calcium levels by amending with lime if necessary. Choose resistant varieties. Provide shade during warmer periods.

Pacific Northwest Specific Challenges: Our mild summers generally favor Romaine lettuce, but the dry-summer conditions mean you need to be vigilant about watering, especially during July and August. Slugs can be a major problem, especially in our wet springs. Keep an eye out for them and take preventative measures early in the season. Late blight is less of a concern for lettuce than for tomatoes and potatoes, but good air circulation and avoiding overhead watering can help prevent any potential issues.

Companion planting can help your Romaine thrive in the Pacific Northwest. Carrots are good companions because their scent deters lettuce root aphids. Radishes are quick to mature and can be harvested before the lettuce needs the space, plus they help break up the soil. Strawberries make excellent ground cover and don't compete with lettuce for nutrients. Chives and onions repel many pests, including aphids and slugs.

Avoid planting Romaine near celery and parsley, as these can attract similar pests and compete for resources.