Mustard Greens in Zone 6A — Pacific Northwest

Mustard greens are a fantastic addition to your Pacific Northwest garden. Their peppery bite adds a unique flavor to salads and stir-fries, and they thrive in our mild summers and cool nights. Plus, there's real satisfaction in harvesting fresh greens nearly year-round in our temperate climate.

While we don't have the blazing heat of other regions, our 148-day growing season and overcast spring days do present some challenges. But with a little planning, you can easily enjoy a bountiful harvest of mustard greens.

Starting mustard greens indoors is an option, but honestly, direct sowing is often easier in our climate. However, if you're eager to get a head start, especially after a cool, wet spring, you can start seeds indoors from late March through mid April, about 3 weeks before you plan to transplant.

Use seed trays with a good seed-starting mix and provide warmth (a heat mat helps) and plenty of light from a grow light. Remember to water from the bottom to prevent damping off; set the tray in a shallow dish of water until the surface looks moist. Our slow springs mean indoor starts can give you a jump on the season.

You can transplant your mustard greens seedlings outdoors from late April through early June, once the soil has warmed up a bit. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space them 6-12 inches apart in well-drained soil. Keep an eye on the weather forecast – a late frost can still happen, so be prepared to cover your seedlings if necessary.

Direct sowing mustard greens is a breeze in the Pacific Northwest. You can sow seeds directly into your garden beds from mid April through early August, giving you a long harvest window.

Prepare your soil by loosening it and adding compost. Sow seeds about ¼ inch deep and space them 6-12 inches apart. Keep the soil consistently moist, especially during germination. Direct sowing is a great way to succession plant for a continuous supply of fresh greens.

Mustard greens need consistent moisture, but overwatering is a problem, especially with our wet springs. During our dry summer months, you'll need to water more frequently. Aim for about 1 inch of water per week, either from rainfall or irrigation.

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 springs.

Underwatering can cause the leaves to become spicier and may trigger bolting. Overwatering can lead to root rot, especially in heavy clay soils. Mulching with straw or compost helps retain moisture and regulate soil temperature.

You can expect your first harvest of mustard greens from late May through mid October, about 45 days after planting. Young leaves have a milder flavor, while larger leaves are spicier.

Harvest by snipping off the outer leaves, allowing the inner leaves to continue growing. This cut-and-come-again method will provide you with a continuous harvest throughout the season. As the first frost approaches in early October, harvest any remaining leaves, even if they're small, as they may not survive a hard freeze.

Here are some common problems you might encounter with mustard greens in the Pacific Northwest:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. Small dark beetles jump when disturbed.
• What causes it: These beetles are most active in spring, attacking young seedlings. Our cool spring soils slow seedling growth, making them more vulnerable.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Try kaolin clay or neem oil. Interplant with basil or catnip.

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: Aphids thrive in warm weather. Although our summers are mild, aphid populations can still explode.
• How to fix/prevent it: A strong spray of water knocks them off. Encourage ladybugs and lacewings. Use insecticidal soap or neem oil. Avoid excess nitrogen fertilizer.

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings.
• What causes it: These caterpillars are the larvae of white cabbage butterflies. They love brassicas.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs like thyme or sage.

Bolting in Heat

• What it looks like: Plant sends up a flower stalk. Leaves become tough and bitter.
• What causes it: Mustard greens bolt when temperatures rise consistently above their comfort zone. Even our mild summers can trigger this.
• How to fix/prevent it: Time plantings for cool weather (spring/fall). Choose bolt-resistant varieties. Provide shade during warm spells. Mulch to keep soil cool. Harvest before bolting progresses.

Pacific Northwest Specific Challenges: Our mild summers help prevent extreme bolting, but our cool, wet springs can encourage flea beetle infestations and fungal diseases. Keep a close eye on your plants, and adjust your watering and pest control strategies as needed.

Companion planting can help your mustard greens thrive. Onions and garlic deter pests like aphids and cabbage worms. Beets improve soil health and provide nutrients. Dill attracts beneficial insects that prey on pests. Lettuce provides ground cover and helps retain moisture. Avoid planting mustard greens near strawberries, as they can compete for nutrients. Also, avoid tomatoes as they can attract similar pests.