Green Onions in Zone 8A — Pacific Northwest

Green onions are a fantastic addition to any Pacific Northwest garden. Their mild, fresh flavor elevates everything from salads to stir-fries, and they're incredibly easy to grow here. Plus, the cool nights we get in the summer seem to make them even sweeter.

Our wet springs and the risk of late blight can be a concern, but with a little planning, you can enjoy a steady supply of green onions throughout our long, mild fall. With a 203-day growing season, you have plenty of time to get multiple harvests.

You can transplant green onion starts outdoors from mid-March through early April. Before planting, be sure to 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 transplants about 2-3 inches apart in well-drained soil. Keep an eye on the weather forecast at this time of year; we often get unexpected cold snaps and overcast spring days that can stress young plants.

Direct sowing is the preferred method for green onions, and it's incredibly simple. You can sow seeds directly into the garden from mid-March through mid-August. Green onions appreciate soil temperatures around 60°F, so you might want to wait until the soil has warmed up a bit in spring.

Prepare the soil by loosening it and removing any rocks or debris. Sow seeds about ¼ inch deep and 2-3 inches apart. Keep the soil consistently moist until the seeds germinate. For a continuous harvest, sow a new batch of seeds every few weeks. Don't forget you can also plant the root ends of store-bought green onions!

Green onions need consistent moisture to thrive, especially during our dry summer months. While we don't experience extreme heat here in the Pacific Northwest, our dry summers and shallow-rooted onions mean they can dry out quickly. The key is to find the right balance.

During the wet springs, you might not need to water at all, but once the dry summer months hit, check the soil regularly. Stick your finger about 2 inches deep; if the soil feels dry, it's time to water. Aim for about 1 inch of water per week, watering at the base of the plants to avoid wetting the foliage.

Overwatering can lead to rot, while underwatering results in tough, strong-tasting stalks. Yellowing or drooping leaves can indicate either issue. A light layer of mulch, like straw or shredded leaves, will help retain moisture and keep the soil cool.

You can expect your first harvest of green onions starting in mid-May and continuing through early November. Green onions are typically ready to harvest about 60 days after planting, when the stalks are about pencil-thick. Don't worry about waiting for a bulb to form; you're harvesting the green stalks.

You can either pull the entire plant or cut the stalks about an inch above the soil line. If you cut them, they'll often regrow, giving you multiple harvests from a single planting. As late October approaches and the risk of frost increases, 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 leaves, stunted growth, and small white maggots at the base of the plant or in the bulb.
• What causes it: These pests lay their eggs near the base of onion plants, and the larvae burrow into the bulbs.
• How to fix/prevent it: Use row covers to prevent adult flies from laying eggs. Introduce beneficial nematodes to the soil. Rotate crops annually.

Thrips

• What it looks like: Silvery or white streaks on the leaves, distorted growth, and tiny, slender insects on the plant.
• What causes it: These tiny insects suck the sap from leaves, causing damage and weakening the plant.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Use insecticidal soap or neem oil.

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: 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. Plant resistant varieties. Solarize the soil in summer to kill the fungus.

Pacific Northwest Specific Challenges: Our mild heat generally isn't an issue for green onions. However, our wet springs can create favorable conditions for fungal diseases like downy mildew, so good air circulation and avoiding overhead watering are crucial. Slugs can also be a nuisance, especially for young plants, so use appropriate control methods.

Companion planting can help your green onions thrive! Carrots are excellent companions because their scent deters onion flies, while the onions deter carrot root flies. Lettuce benefits from the shade provided by green onions, and both tomatoes and peppers enjoy the pest-repelling properties of onions. Beets are also good companions, as they don't compete for the same nutrients.

Avoid planting green onions near beans or peas. Onions can inhibit the growth of these legumes.