Romaine Lettuce in Zone 8B — Pacific Northwest

Romaine lettuce is a staple in salads, and it's surprisingly easy to grow your own here in the Pacific Northwest. The cool nights we get, even during our mild summers, help keep the leaves crisp and flavorful. Plus, nothing beats the satisfaction of harvesting fresh lettuce from your garden for a BLT.

While the PNW isn't known for scorching heat, our springs can be cool and wet, and we can get the occasional heat wave. But with a little planning and attention to timing, you can enjoy a long season of homegrown Romaine, thanks to our 210-day growing season.

Starting Romaine lettuce indoors isn't strictly necessary in our climate, but it can give you a head start, especially if you're eager for an early harvest. Sow seeds indoors from mid-February through early March, about four weeks before you plan to transplant. Use seed trays or small pots filled with a good seed-starting mix.

Keep the soil consistently moist (bottom watering works great to avoid damping off) and provide plenty of light. Overcast spring days can mean leggy seedlings if you don't supplement with grow lights. A heat mat can help with germination, but isn't essential.

Transplant your Romaine seedlings outdoors from late March through mid-April, after they've developed a few sets of true leaves. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space the seedlings 8-10 inches apart in well-drained soil. Be prepared to cover them with row covers if we get a late cold snap; those cool, wet springs can sometimes throw us a curveball.

Direct sowing Romaine lettuce is a straightforward option, especially for later harvests. Sow seeds directly into the garden from early March through mid-August. Choose a spot with full sun to partial shade, and make sure the soil is loose and well-draining.

Gently press the seeds into the soil, about ¼ inch deep, and keep them consistently moist. Thin the seedlings to 8-10 inches apart once they're a few inches tall. Direct sowing is great for succession planting, ensuring a continuous supply of lettuce.

Romaine lettuce needs consistent moisture to produce crisp, tender leaves, but overwatering can lead to problems. Here in the PNW, our dry summers mean you'll need to pay attention to watering, but it's not as intense as in hotter climates.

In the spring and fall, when rainfall is more frequent, you might only need to supplement with an inch of water per week, if at all. During our drier summer months, increase that to about 1-1.5 inches per week. Always check the soil moisture before watering; stick your finger about 2 inches deep. 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 sometimes humid conditions. Mulching around your lettuce plants with straw or wood chips helps retain moisture and keeps the soil cool. Underwatering leads to wilting and bitter leaves, while overwatering can cause root rot.

You can expect your first harvest of Romaine lettuce from mid-May through early November, depending on when you planted. Start harvesting outer leaves when they are about 6-8 inches long. This allows the plant to continue producing new leaves.

Alternatively, you can harvest the whole head when it feels firm and full-sized, but before the center stem starts to elongate. This elongation is a sign that the plant is bolting. To harvest, simply cut the leaves or the entire head at the base with a sharp knife.

To encourage continued production, keep the plant watered and fertilized lightly. As the first frost approaches in early November, harvest any remaining heads to prevent them from being damaged by the cold.

Romaine lettuce, like any garden vegetable, can face a few challenges. Here are some common problems in the Pacific Northwest:

Bolting in Heat *What it looks like:* The lettuce plant sends up a tall flower stalk. The leaves become tough and bitter. *What causes it:* Extended warm temperatures, which can happen even in our mild PNW summers. *How to fix/prevent it:* Time your plantings for cooler weather. Choose bolt-resistant varieties. Provide shade with shade cloth during warm spells. Mulch to keep the soil cool. Harvest promptly if you see signs of bolting.

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:* Rapidly reproducing sap-sucking insects that thrive in warm weather. *How to fix/prevent it:* Knock them off with a strong spray of water. Encourage natural predators like ladybugs. Use insecticidal soap for heavy infestations.

Slugs *What it looks like:* Irregular holes in leaves, especially on lower leaves. Silvery slime trails. *What causes it:* Slugs love the moist conditions we often have in the PNW, especially in spring and fall. *How to fix/prevent it:* Use beer traps. Apply iron phosphate bait. Remove hiding spots like weeds and debris. Water in the morning so the soil surface dries out by evening.

Tip Burn *What it looks like:* Brown, dried edges on inner lettuce leaves. *What causes it:* Calcium uptake issues due to inconsistent watering, especially during warm spells. *How to fix/prevent it:* Water consistently. Ensure good soil calcium levels. Choose resistant varieties. Provide shade in warm weather.

Pacific Northwest Specific Challenges: Our cool soil in spring can slow down growth, so starting indoors or using row covers can help. While late blight is more of a concern for tomatoes and potatoes, it's still wise to practice good garden hygiene to prevent its spread. The biggest challenge is slugs, which thrive in our damp climate, so be vigilant with your slug control methods.

Companion planting can help your Romaine lettuce thrive. Carrots are good companions because their scent deters lettuce root aphids. Radishes are quick to mature and can help break up the soil, benefiting the lettuce roots. Strawberries provide ground cover, helping to retain moisture and suppress weeds. Chives and onions deter aphids and other pests with their strong scent.

Avoid planting Romaine lettuce near celery and parsley. Celery competes for nutrients and water, while parsley can attract pests that also affect lettuce. Choosing the right companions can lead to healthier, more productive lettuce plants in your Pacific Northwest garden.