Green Onions in Zone 4B — Midwest

Green onions are a must-grow in any Midwest garden. They're so easy to grow, add a fresh bite to everything from grilled burgers to summer salads, and give you that satisfying "I grew this!" feeling. Plus, they're one of the first things you can harvest, which is a real treat after our long winters.

Our Midwest weather can be unpredictable, with temperature swings in spring and the occasional summer heat spells. But green onions are pretty adaptable, and with a little attention to timing, you can have a steady supply throughout our 138-day growing season.

You can transplant green onion seedlings outdoors starting in mid-April through early May, once the soil can be worked. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space the seedlings about 2-3 inches apart in rows. Keep an eye on the forecast; we sometimes get a late frost in the Midwest, even into early May. If frost threatens, cover your transplants with row covers or blankets to protect them.

Direct sowing is the easiest way to grow green onions in the Midwest. You can start sowing seeds from mid-April through mid-July for a continuous harvest. Choose a spot with full sun to partial shade and fertile soil.

Before sowing, loosen the soil and remove any rocks or debris. Sow seeds about ¼ inch deep and 2-3 inches apart. Keep the soil consistently moist until the seeds germinate, which usually takes about a week or two. 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 thrive, especially in our Midwest summers. Aim to keep the soil evenly moist, but not waterlogged. The finger test is a good way to check: stick your finger about 2 inches into the soil, and if it feels dry, it's time to water.

During the hotter parts of summer, your green onions will likely need about an inch of water per week, either from rainfall or irrigation. It's best to water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid climate. Overhead watering is fine if done early in the morning so the leaves can dry out before nightfall.

If the leaves start to yellow or droop, it could be a sign of underwatering. If the leaves turn pale and the bulbs become soft, you might be overwatering. Mulching around your green onions with straw or shredded leaves can help retain moisture and suppress weeds, especially helpful during our occasional summer heat spells.

You can start harvesting green onions about 60 days after planting, typically from mid-June through early October in the Midwest. Look for stalks that are at least pencil-thick. You can either pull up the entire plant or snip off the green tops about an inch above the soil.

If you cut the tops, the green onions will regrow, giving you multiple harvests. To encourage continued production, make sure to keep the soil moist and fertilize lightly after each harvest. As the first frost approaches in late September, 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 Midwest:

Onion Maggots

• What it looks like: Wilting or yellowing plants, stunted growth, and small white maggots feeding on the roots and bulbs.
• What causes it: These pests are attracted to onions and lay their eggs near the base of the plants. The maggots hatch and burrow into the roots.
• How to fix/prevent it: Use row covers to prevent the adult flies from laying eggs. Apply beneficial nematodes to the soil to control the maggots. Remove and destroy any infested plants.

Thrips

• What it looks like: Tiny, slender insects on the leaves, causing silvery or white streaks and distorted growth.
• What causes it: Thrips are attracted to dry, hot conditions.
• How to fix/prevent it: Keep plants well-watered. Spray with insecticidal soap or neem oil. Encourage beneficial insects like ladybugs and lacewings.

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: Roots turn pink or reddish, causing stunted growth and yellowing leaves.
• What causes it: A soilborne fungus that thrives in warm, wet conditions and high soil temperatures.
• How to fix/prevent it: Improve soil drainage. Rotate crops to avoid planting onions in the same spot year after year. Use resistant varieties if available. Solarize the soil during the summer to kill the fungus.

Midwest Specific Challenges: Our moderate-to-hot summers and moderate-to-humid conditions can create a favorable environment for fungal diseases like downy mildew. Be sure to provide good air circulation and avoid overhead watering to minimize these problems. Keep an eye out for pests like onion maggots and thrips, especially during dry spells.

Green onions are great companions for many plants in your Midwest garden. Carrots benefit from green onions because the onion's scent deters carrot root flies. Lettuce also enjoys the company of green onions, as they help repel aphids. Tomatoes and peppers thrive near green onions because they deter pests like spider mites and aphids. Beets benefit from green onions as well; the onions help to deter leaf miners.

Avoid planting green onions near beans and peas. Onions can inhibit the growth of these legumes, potentially reducing your harvest.