Green Onions in Zone 6B — Pacific Northwest

Green onions are a must-grow in any Pacific Northwest garden. Their mild, fresh flavor elevates everything from stir-fries to salads, and they're incredibly versatile in the kitchen. Plus, those cool nights we get here really help develop a sweeter, less pungent onion flavor.

Our wet springs and relatively short summers can present challenges, but green onions are quick to mature, making them a reliable crop even with our 162-day growing season. Proper timing and a little attention will ensure a bountiful harvest.

You can transplant green onion seedlings outdoors in early April through early May. Before planting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the temperature swings and stronger sunlight.

Space your transplants 2-3 inches apart in rows. Keep an eye on the weather forecast; a late cold snap can set them back. If unexpected overnight temperatures dip near freezing, cover them with horticultural fleece or cloches.

Direct sowing is the easiest way to grow green onions here. You can start sowing in early April and continue through late July for a continuous harvest. The soil should be at least 50°F for optimal germination.

Prepare your garden bed by loosening the soil and amending with compost. Sow seeds about ¼ inch deep and 2-3 inches apart. Keep the soil consistently moist until seedlings emerge. For a fun and easy start, you can also plant the root ends of store-bought green onions – just stick them in the ground, and they'll regrow!

Green onions need consistent moisture to produce tender, mild stalks. Because they have shallow roots, they can dry out quickly, especially during our dry summer months. While our summers aren't scorching, consistent watering is key.

During our wet springs, you likely won't need to water much beyond what nature provides. However, once the dry summer months arrive, check the soil moisture regularly. Stick your finger about 2 inches deep; if it feels dry, it's time to water. Aim for about 1 inch of water per week, delivered in one or two deep soakings.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases, even though we have relatively low humidity in the summer. Signs of underwatering include wilting or yellowing leaves, while overwatering can lead to root rot. A light layer of mulch, like straw or shredded leaves, will help retain moisture and suppress weeds.

You can expect your first harvest of green onions in early June through mid-October, about 60 days after sowing. They're typically ready when the stalks are about pencil-thick. Don't wait too long, or they can get tough.

To harvest, you can either pull the entire plant or cut the stalks about an inch above the soil line. If you cut them, they'll usually regrow for a second harvest. As our first frosts approach in early October, harvest any remaining green onions to use fresh or preserve.

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

Onion Maggots

• What it looks like: Wilting or yellowing plants, stunted growth, and small white maggots feeding on the roots and bulb.
• What causes it: Onion maggots are the larvae of a fly that lays its eggs near onion plants. They thrive in cool, moist conditions, like our springs.
• How to fix/prevent it: Use row covers to prevent the flies from laying eggs. Companion plant with carrots, as their scent can deter the flies. Remove and destroy any infested plants.

Thrips

• What it looks like: Silvery streaks or white patches on the leaves, distorted growth, and tiny, slender insects on the plants.
• What causes it: Thrips are tiny insects that suck plant juices. They are more prevalent during our dry summer months.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Spray plants with a strong stream of water or insecticidal soap.

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. Different species affect different plants.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base, never overhead. Copper-based fungicides for prevention. Plant resistant varieties where available.

Pink Root

• What it looks like: Pink or reddish roots, stunted growth, and yellowing leaves.
• What causes it: A soilborne fungus that infects the roots, hindering water and nutrient uptake.
• How to fix/prevent it: Improve soil drainage. Rotate crops to avoid planting onions in the same spot year after year. Plant resistant varieties.

Pacific Northwest Specific Challenges: Our mild summers generally reduce the severity of some pest problems, but our cool, wet springs can favor diseases like downy mildew. Be sure to monitor your plants regularly and take action quickly to prevent problems from spreading. Slugs can be a minor issue, especially for young seedlings.

Companion planting can help your green onions thrive. Carrots are excellent companions because their scent deters onion flies, and the onions, in turn, repel carrot root flies. Lettuce grows well alongside green onions, as they have similar needs and don't compete for resources.

Tomatoes and peppers also benefit from being near green onions, as the onions can repel some common pests. Beets are good companions as well, helping to loosen the soil and improve drainage. Avoid planting green onions near beans or peas, as they can inhibit each other's growth.