Green Onions in Zone 7B — Pacific Northwest

Green onions are a must-grow in the Pacific Northwest. Their mild, fresh flavor elevates everything from salads to stir-fries, and they're incredibly versatile in the kitchen. Plus, the satisfaction of snipping fresh green onions from your garden throughout our long, mild fall is hard to beat.

While we PNW gardeners do have to contend with cool springs and occasional bouts of late blight, green onions are surprisingly resilient. With our 193-day growing season, you'll find plenty of time to get multiple harvests from a single planting.

You can transplant green onion starts outdoors from mid-March through mid-April. Before planting, make sure to harden off your seedlings. Give them about a week of gradual exposure to the outdoors to acclimate them to the PNW weather, especially those overcast spring days.

Space your transplants about 2-3 inches apart in well-drained soil. Keep an eye on the weather forecast – a late cold snap can still happen, so be prepared to cover them if temperatures dip near freezing.

Direct sowing is the easiest way to grow green onions in the PNW. You can start sowing seeds from mid-March through mid-August for a continuous supply. Green onions aren't too fussy about soil, but they do prefer well-drained soil that's been amended with compost.

Sow seeds about ¼ inch deep and 2-3 inches apart. Keep the soil consistently moist until the seedlings emerge. For an even easier start, you can also plant the root ends of store-bought green onions in water until they sprout, then transplant them directly into your garden.

Green onions need consistent moisture to thrive, but they don't like soggy soil. In our PNW climate, the watering schedule will vary with the seasons. During our wet springs, you might not need to water them at all, especially if you get regular rainfall.

Once our dry summer months arrive, check the soil moisture regularly. Stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Aim for about 1 inch of water per week, delivered at the base of the plants to avoid wetting the foliage. This helps prevent fungal diseases, which can become more prevalent even with our dry-summer humidity.

Signs of underwatering include wilting or yellowing leaves. Overwatering can lead to root rot, so watch for stunted growth and mushy stems. A layer of mulch, like straw or shredded leaves, can help retain moisture and keep the soil cool during our mild summers.

You can expect your first harvest of green onions starting in mid-May and continuing through early November. They're usually ready to harvest about 60-70 days after planting, when the stalks are about pencil-thick. Don't worry if they're not perfectly uniform – you can harvest them at any size you prefer.

To harvest, you can either pull the entire plant or snip the green stalks about an inch above the soil line. If you leave the roots intact, the green onions will often regrow, giving you multiple harvests. As our first frost approaches in late October, harvest any remaining green onions to use fresh or freeze for later.

Here are some common problems you might encounter with green onions in the PNW:

Onion Maggots

• What it looks like: Yellowing and wilting plants, often with maggots visible near the base of the bulb.
• What causes it: These pests lay their eggs near the base of the plants, and the larvae burrow into the bulbs.
• How to fix/prevent it: Use row covers to prevent the adults from laying eggs. Introduce beneficial nematodes to the soil.

Thrips

• What it looks like: Small, silvery streaks on the leaves, often accompanied by distorted growth.
• What causes it: Tiny insects that suck the sap from the leaves.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Insecticidal soap can also be effective.

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: Oomycete pathogen that spreads in cool, humid conditions via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base, never overhead. Copper-based fungicides for prevention.

Pink Root

• What it looks like: Roots turn pink or reddish, and the plants may be stunted.
• What causes it: A soilborne fungus that thrives in warm, wet conditions.
• How to fix/prevent it: Improve soil drainage. Rotate crops to avoid planting onions in the same spot year after year.

Pacific Northwest Specific Challenges: Our mild summers and dry-summer rainfall generally help reduce the severity of some onion diseases. However, our cool springs can slow down growth and make the plants more susceptible to early pest infestations. Keep an eye out for slugs, which love tender young onion shoots.

Companion planting can help your green onions thrive in the PNW. Carrots are excellent companions because they deter onion flies, while the onions deter carrot root flies. Lettuce benefits from the shade provided by green onions, and the onions help repel aphids that can plague lettuce.

Tomatoes and peppers also benefit from being planted near green onions, as the onions can help deter pests like spider mites. Beets and green onions are great neighbors, as they both have similar soil and watering needs. Avoid planting green onions near beans or peas, as they can inhibit each other's growth.