Green Onions in Zone 5A — Midwest

Green onions are a must-grow in any Midwest garden. Their fresh, mild flavor elevates everything from summer salads to grilled meats, and they're so versatile you'll find yourself snipping them almost daily. Plus, they're incredibly satisfying to grow; a quick snip and they're ready to use.

Our Midwest weather can be unpredictable, with temperature swings in spring and the occasional summer heat spell. But don't worry, green onions are forgiving and fast-growing, fitting perfectly into our 157-day growing season. You'll be harvesting fresh onions in no time.

You can transplant green onion seedlings outdoors from early April through early May, giving them a head start. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Midwest weather.

Plant your seedlings 2-3 inches apart in well-drained soil. Keep an eye on the forecast, as late frosts are always possible in early spring. Cover the seedlings with a frost blanket if temperatures dip unexpectedly.

Direct sowing is the easiest way to grow green onions. From early April through late July, sow seeds directly into the garden. Green onions aren't picky, but they do best in soil that's loose, fertile, and around 50-75°F.

Plant seeds about ½ inch deep and 2-3 inches apart. Keep the soil consistently moist until they germinate. For an even easier start, you can also plant the root ends of store-bought green onions in water until they sprout, then transplant to the garden.

Green onions need consistent moisture to produce tender, flavorful stalks. In our Midwest climate, with moderate-to-humid summers and the occasional heat spell, watering is key. They aren't drought-tolerant, and their shallow roots dry out quickly.

During the spring and fall, when temperatures are cooler and rainfall is more frequent, aim for about 1 inch of water per week, either from rain or irrigation. Check the soil moisture by sticking your finger about 2 inches deep. If it feels dry, it's time to water. In the heat of summer, you might need to water more frequently, especially during those summer heat spells.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid climate. Signs of underwatering include yellowing leaves and stunted growth. Overwatering, on the other hand, can lead to root rot, so ensure your soil drains well. Adding a layer of mulch, like straw or shredded leaves, helps retain moisture and regulate soil temperature.

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

Harvest by either pulling the entire plant or snipping the green stalks about an inch above the soil line. If you cut them, they'll often regrow for multiple harvests. As we approach the first frost in early October, harvest any remaining 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 near the roots.
• What causes it: These pests are attracted to onions and lay their eggs near the base of the plant. Our variable spring weather can sometimes favor their development.
• How to fix/prevent it: Use row covers to prevent the adult flies from laying eggs. Introduce beneficial nematodes to the soil. 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 plant.
• What causes it: Thrips are tiny insects that suck plant sap. Hot, dry weather can exacerbate thrip infestations.
• How to fix/prevent it: Spray plants with a strong stream of water to dislodge thrips. Use insecticidal soap or neem oil. Encourage beneficial insects like ladybugs.

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, plants are stunted, and leaves may yellow or wilt.
• What causes it: A soilborne fungus that thrives in warm, wet conditions. Clay soil, common in the Midwest, can worsen the problem by retaining moisture.
• How to fix/prevent it: Improve soil drainage by adding organic matter. Rotate crops to avoid planting onions in the same spot year after year. Solarize the soil in summer to kill the fungus.

Midwest Specific Challenges: The combination of moderate-to-hot heat, moderate-to-humid humidity, and wet-summer rainfall in the Midwest creates conditions that can favor fungal diseases like downy mildew and root rot. Good air circulation and proper watering practices are essential for healthy green onions.

Companion planting can really boost your green onion crop. Carrots are great companions because they deter onion flies, while the onions repel carrot rust flies. Lettuce and other leafy greens benefit from the pest-repelling properties of green onions. Tomatoes and peppers also thrive near green onions, as the onions can help deter aphids and other pests. Beets are also good companions, improving the soil health around the onions.

Avoid planting green onions near beans or peas. These legumes can inhibit the growth of onions, as they compete for the same nutrients in our fertile soil.