Green Onions in Zone 4A — Great Plains

Green onions are a must-grow in any Plains garden. Their mild, fresh flavor adds a zing to everything from summer salads to grilled dishes, and they're incredibly versatile in the kitchen. Plus, there’s nothing quite as satisfying as snipping a few fresh green onions right from your backyard, especially when the grocery store prices seem sky-high.

Sure, we've got our share of extreme weather here on the Plains – temperature swings, hail, and the occasional drought. But with a bit of planning and attention to timing, you can easily grow a continuous supply of green onions within our 138-day growing season.

Transplanting green onions is a great way to get a head start. Aim to get your transplants in the ground mid April through early May. This gives them a chance to establish before the real heat of summer hits.

Before planting, be sure to harden off your seedlings. This means gradually exposing them to outdoor conditions for about a week. Plant them 2-3 inches apart in well-drained soil.

Keep an eye on the weather forecast, as those early spring days can still bring unexpected frosts. Have row covers or blankets ready to protect your young plants if needed.

Direct sowing is the easiest way to grow green onions here on the Plains. Sow seeds mid April through mid July for a continuous harvest. Green onions germinate best when soil temperatures are between 60-70°F.

Prepare your soil by loosening it and adding some compost or well-rotted manure. Plant seeds about ½ inch deep and 2-3 inches apart. Keep the soil consistently moist until the seedlings emerge.

Here's a Plains-specific tip: you can also plant the root ends of store-bought green onions! Just stick the white root end in the soil, and new green shoots will emerge.

Green onions need consistent moisture to thrive, but they don't like soggy soil. Here on the Plains, with our hot summers and variable rainfall, watering can be tricky.

In the spring and fall, when temperatures are cooler, you might only need to water once or twice a week. During the heat of summer, especially when the wind is whipping, you may need to water every day or every other day. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation.

Water at the base of the plants to avoid wetting the foliage, which can encourage disease in our low-to-moderate humidity. Signs of underwatering include wilting or yellowing leaves, while overwatering can lead to root rot. A layer of mulch, like straw or shredded bark, will help retain moisture and keep the soil cool during the hottest months.

You can start harvesting green onions about 60 days after planting, so expect your first harvest from mid June through early October, depending on your planting date. They're ready to harvest when the stalks are about pencil-thick.

To harvest, you can either pull up the entire plant or snip off the green tops about an inch above the soil line. If you cut them, the plants will regrow, giving you multiple harvests.

To keep your green onions producing throughout the season, be sure to water and fertilize them regularly. As our first frost approaches in late September, harvest any remaining green onions or consider covering them with a cold frame to extend the harvest a bit longer.

Even with the best care, green onions can sometimes run into problems. Here are a few common issues we see on the Plains:

Onion Maggots

• What it looks like: Wilting plants, yellowing leaves, and small white maggots feeding on the roots and bulb.
• What causes it: These pests are attracted to the smell of onions and lay their eggs near the base of the plants.
• How to fix/prevent it: Use row covers to prevent the flies from laying eggs. Apply beneficial nematodes to the soil. Remove and destroy any infested plants.

Thrips

• What it looks like: Small, silvery streaks on the leaves, distorted growth, and tiny black specks (thrip droppings).
• What causes it: Thrips are tiny insects that suck the sap from plants, thriving in hot, dry conditions.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Spray plants with insecticidal soap or neem oil. Water regularly to reduce plant stress.

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 bulbs are small.
• What causes it: A soilborne fungus that thrives in warm, moist conditions.
• How to fix/prevent it: Practice crop rotation. Improve soil drainage. Plant resistant varieties. Solarize the soil in the summer to kill the fungus.

Great Plains Specific Challenges: Our hot heat can stress plants, making them more susceptible to pests and diseases. The low-to-moderate humidity can help reduce some fungal issues, but our variable rainfall means you need to be vigilant about watering. Watch out for hail damage, which can quickly decimate a crop of green onions.

Companion planting can help your green onions thrive. Carrots are great companions because their scent repels onion flies. Lettuce benefits from the shade provided by green onions, which helps prevent bolting in the summer heat. Tomatoes and peppers also benefit from being near green onions, as they can help deter certain pests. Beets are good companions because they don't compete for the same nutrients in the soil.

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