Green Onions in Zone 4B — Great Plains

Green onions are a must-grow in our Zone 4B gardens. Their fresh, mild flavor elevates everything from summer salads to grilled meats. Plus, they’re incredibly versatile, giving you a steady supply of greens throughout our short but intense growing season.

Sure, we face extreme temperature swings and occasional hail here on the Plains, but green onions are surprisingly resilient. With a little attention to timing, you can easily harvest them within our 149-day growing season.

You can transplant green onion starts outdoors from early April through early May. Before planting, it's important to harden them off. Give them about a week of gradual exposure to the outdoors before planting in their final spot.

Space your transplants about 2-3 inches apart in rows. Keep an eye on the weather; a late frost can happen, so be ready to cover your seedlings if needed. Wind protection is essential for young transplants to prevent damage.

Direct sowing is the easiest way to grow green onions here. Sow seeds from early April through mid July for a continuous harvest. Green onions are very forgiving.

Prepare your soil by loosening it and adding some compost. Aim for a soil temperature of at least 50°F. Sow seeds about ¼ inch deep, spacing them 2-3 inches apart. For an even easier start, you can even plant the root ends of store-bought green onions – just stick them in the ground and keep them watered!

Green onions need consistent moisture to thrive, but they definitely don't want to be soggy. This is especially true given our hot summers and variable rainfall here on the Plains. Aim for about 1 inch of water per week, either from rain or irrigation.

During hot, dry spells, you'll probably need to water more often. Use the finger test: if the top 2 inches of soil feel dry, it's time to water. Water at the base of the plants to avoid wetting the foliage, which can encourage disease in our low-to-moderate humidity.

Yellowing leaves can be a sign of underwatering, while mushy, rotting stalks indicate overwatering. A light layer of mulch, like straw or shredded leaves, can help retain moisture and regulate soil temperature, which is helpful in our extreme climate.

You can start harvesting green onions around early June, and continue through early October. Green onions are typically ready to harvest about 60 days after planting, when the stalks are about pencil-thick. Don't worry if it takes a bit longer; they're pretty flexible.

To harvest, you can either pull up the entire plant or cut the stalks about an inch above the soil line. If you cut them, they'll often regrow for another harvest. As our first frost approaches in early October, harvest any remaining green onions to enjoy before the ground freezes.

Here are a few common problems to watch out for with green onions in our region:

Onion Maggots

• What it looks like: Yellowing or wilting plants, stunted growth, and small white maggots feeding on the roots and bulb.
• What causes it: These pests thrive in moist soil and can be a problem, especially during wet springs.
• How to fix/prevent it: Use row covers to prevent the adult flies from laying eggs. Rotate crops each year, and remove any infested plants promptly.

Thrips

• What it looks like: Small, slender insects that cause silvery streaks and distorted growth on leaves.
• What causes it: Thrips are more prevalent during hot, dry periods, which we often experience in the Plains.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Insecticidal soap can also be effective.

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.

Pink Root

• What it looks like: Roots turn pink or reddish, and the plant's growth is stunted.
• What causes it: A soilborne fungus that thrives in warm soil.
• How to fix/prevent it: Improve soil drainage and rotate crops. Plant resistant varieties if available.

Great Plains Specific Challenges: Our combination of hot heat, low-to-moderate humidity, and variable rainfall can stress green onions, making them more susceptible to pests and diseases. Consistent watering, good air circulation, and regular monitoring are key to keeping your plants healthy.

Companion planting can really help your green onions thrive. Carrots are great companions because their scent deters onion flies. Lettuce benefits from the pest-repelling properties of green onions.

Tomatoes and peppers also do well planted near green onions, as the onions can help deter certain pests that bother these crops. Beets are another good companion, as they don't compete for the same nutrients and can help loosen the soil.

Avoid planting beans or peas near green onions. They tend to inhibit each other's growth, and you'll get better yields if you keep them separated.