Green Onions in Zone 5A — Great Plains

Green onions are a must-grow for any Plains gardener! Their fresh, mild flavor adds a zing to everything from summer salads to grilled dishes. Plus, they're incredibly versatile – you can use the whole plant, from the white bulb to the green tops.

Our Great Plains climate can throw curveballs with extreme weather. But don't worry, green onions are quick to mature and can handle some cool weather. With our 168-day growing season, you have plenty of opportunity to get several harvests.

You can transplant green onion seedlings outdoors from late March through late April. Before you move them outside, harden them off. This means giving them gradually longer periods of outdoor exposure over about a week.

Space your transplants about 2-3 inches apart. Keep an eye on the weather forecast – a late-season cold snap or even a bit of hail is always possible here on the Plains. Row covers can provide extra protection if needed.

Direct sowing is the easiest way to grow green onions here on the Plains. You can sow seeds directly into the garden from late March through late July. This gives you a long window for successive plantings.

Make sure your soil is loose and well-drained. Green onions prefer a soil temperature of at least 50°F for good germination. Sow seeds about ½ inch deep and 2-3 inches apart. Water gently but thoroughly after planting. 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, but they don't like soggy soil. During our hot Plains summers, you'll likely need to water them more frequently. A good rule of thumb is to water when the top 2 inches of soil feel dry to the touch – the "finger test."

Aim to give your green onions about 1 inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage, especially with our low-to-moderate humidity. Overhead watering can encourage fungal diseases.

If the leaves start to yellow or wilt, it's a sign of underwatering. If the leaves are pale green and the soil is constantly soggy, you're likely overwatering. A layer of mulch, like straw or shredded leaves, can help retain moisture and regulate soil temperature. This is especially helpful during those extreme temperature swings.

You can expect your first harvest of green onions starting in late May and continuing through mid-October. Green onions are typically ready to harvest about 60 days after planting, or when the stalks are about pencil-thick. Don't worry about getting it exactly right – they're tasty at various sizes.

You can either pull up the entire plant or cut the green tops off about an inch above the soil line. If you cut them, the onions will regrow, giving you multiple harvests. As the first frost approaches in early October, harvest any remaining green onions. They can be chopped and frozen for later use.

Here are some common problems you might encounter growing green onions in the Great Plains:

Onion Maggots

• What it looks like: Wilting or yellowing leaves, stunted growth, and small white maggots feeding on the roots and bulb.
• What causes it: These pests are attracted to the smell of onions. They lay their eggs near the base of the plants, and the larvae burrow into the bulbs.
• How to fix/prevent it: Use row covers to prevent the adult flies from laying eggs. Apply beneficial nematodes to the soil. Rotate your crops each year.

Thrips

• What it looks like: Tiny, slender insects that feed on the leaves, causing silvery streaks and distorted growth.
• What causes it: Thrips thrive in hot, dry conditions, which can be common during our Plains summers.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Use 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.
• 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 may be stunted or wilted.
• What causes it: A soilborne fungus that thrives in warm, moist conditions.
• How to fix/prevent it: Improve soil drainage. Rotate your crops. Plant resistant varieties if available. Soil solarization can help reduce fungal populations.

Great Plains Specific Challenges: Our hot summers can stress green onions, making them more susceptible to pests and diseases. Variable rainfall can also make it challenging to maintain consistent moisture levels. Consistent monitoring and proactive management are key.

Green onions are great companions for many plants in your garden. Carrots benefit because the onion smell deters carrot root flies. Lettuce thrives in the partial shade provided by green onions. Tomatoes and peppers are said to benefit from the pest-repelling properties of onions. Beets also enjoy growing near green onions, as they help deter certain pests.

Avoid planting green onions near beans and peas. Onions can inhibit the growth of these legumes. This is especially important in our region, where we need to maximize the productivity of every plant during our limited growing season.