Green Onions in Zone 7A — Pacific Northwest

Green onions are a must-have in any Pacific Northwest garden. Their fresh, mild flavor elevates everything from stir-fries to salads, and they're incredibly easy to grow in our climate. Plus, there's something deeply satisfying about snipping a few green onions from your garden for dinner on a cool summer evening.

While we might struggle a bit with heat-loving plants, green onions thrive in our long, mild springs and falls. With a little attention to timing, you can enjoy a continuous harvest throughout our 183-day growing season, even with our overcast spring days.

If you're starting green onions indoors, aim to transplant them outdoors from late March through mid April. Before planting, be sure to harden off your seedlings. Give them about a week of gradual exposure to the outdoors, increasing their time outside each day.

When transplanting, space the seedlings 2-3 inches apart in a well-prepared bed. Keep an eye on the weather, as we can still get some unexpected chilly nights in early spring. A row cover can provide extra protection if needed.

Direct sowing is the easiest and most common way to grow green onions in the Pacific Northwest. You have a long window for direct sowing, from late March through early August, which allows for succession planting and a continuous harvest. Green onions don't mind cool soil, but you'll get faster germination as the soil warms up.

Prepare your soil by loosening it and adding some compost for good drainage and fertility. Sow the seeds about ½ inch deep and 2-3 inches apart. Keep the soil consistently moist until the seedlings emerge. You can also plant the root ends of store-bought green onions for a quick start – just stick them in the ground, and they'll regrow!

Consistent moisture is key to growing tender, mild green onions in the Pacific Northwest. While our summers are mild and we don't often see temperatures above 90°F, the dry summer months mean you'll need to pay attention to watering. Green onions have shallow roots and can dry out quickly.

During our wet springs, you may not need to water at all, relying on natural rainfall. As the dry summer months approach, check the soil moisture regularly. Stick your finger in about 2 inches deep; if it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rain or irrigation. Water at the base of the plants to avoid wetting the foliage, which can help prevent fungal diseases in our dry-summer humidity.

Signs of underwatering include yellowing or wilting leaves, while overwatering can lead to rot. A light layer of mulch, such as straw or shredded leaves, can help retain moisture and keep the soil cool during the warmer months.

You can expect your first harvest of green onions from late May through late October, about 60 days after planting. Look for stalks that are at least pencil-thick. You can harvest the entire plant by gently pulling it from the soil, or you can cut the stalks about an inch above the base.

If you cut them, they will often regrow, giving you a continuous harvest. For continued production, make sure to keep the soil moist and fertilize lightly with a balanced fertilizer every few weeks. As our first frost approaches in mid- October, harvest any remaining green onions and store them in the refrigerator.

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

• Onion Maggots
• What it looks like: Yellowing and wilting of leaves, 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 the base of onion plants. The maggots burrow into the bulb and roots.
• How to fix/prevent it: Use row covers to prevent the flies from laying eggs. Apply beneficial nematodes to the soil. Rotate crops each year.
• Thrips
• What it looks like: Silvery streaks on leaves, distorted growth, and tiny black insects visible on the plant.
• What causes it: Thrips are small, slender insects that feed on plant sap. They thrive in warm, dry conditions.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Spray plants with a strong stream of water to dislodge thrips. Insecticidal soap can be used for heavy infestations.
• 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: Downy mildew is caused by an 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 can be used for prevention.
• Pink Root
• What it looks like: Roots turn pink or reddish, plants are stunted, and leaves may yellow.
• What causes it: Pink root is a soilborne fungal disease that is more prevalent in warm soils.
• How to fix/prevent it: Improve soil drainage and avoid overwatering. Rotate crops regularly. Plant resistant varieties if available.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall can actually be beneficial for green onions, reducing the risk of some diseases. However, our cool soil in spring can slow down growth, so be patient. Slugs can also be a nuisance, so use your preferred slug control methods. Late blight is less of a concern for green onions than for tomatoes, but it's still good to be aware of.

Companion planting can help your green onions thrive in the Pacific Northwest. Carrots are excellent companions because their scent deters onion flies. Lettuce also works well, as it provides ground cover that helps retain moisture and suppress weeds.

Tomatoes and peppers benefit from being planted near green onions, as the onions can repel certain pests. Beets are also good companions, as they have different nutrient needs and don't compete with green onions. Avoid planting beans and peas near green onions, as they can inhibit each other's growth.