Green Onions in Zone 5B — Great Plains

Green onions are a must-grow in the Plains. Their mild, fresh flavor elevates everything from grilled burgers to summer salads, and they’re so easy to tuck into any sunny spot. Plus, there's nothing quite like the satisfaction of snipping a few homegrown green onions for a last-minute dinner garnish.

Our Great Plains weather, with its extreme temperature swings and occasional hail, can be a challenge. But green onions are quick to mature, and you can keep them going all season with succession planting. With our 178-day growing season, you have plenty of time to enjoy a continuous harvest.

You can transplant green onions outdoors from late March through mid April. The key is to harden them off first. Give them about a week of gradually increasing exposure to the sun and wind.

When you're ready to plant, space them 2-3 inches apart. Our spring weather can be unpredictable, so keep an eye on the forecast. If a late frost threatens, cover your transplants with a frost blanket.

Direct sowing is the easiest way to grow green onions in the Plains. Start sowing in late March and continue through early August for a continuous supply. Green onions aren't picky.

Just rake the soil smooth, scatter the seeds, and lightly cover them with about ¼ inch of soil. Keep the soil consistently moist. Thin seedlings to 2-3 inches apart once they're a few inches tall. For a super easy start, you can even plant the root ends of store-bought green onions!

Green onions need consistent moisture, but they don't like to be soggy. In our Plains climate, that can be a tricky balance, especially with our hot summers and variable rainfall.

During the spring and fall, when temperatures are milder, check the soil moisture every few days. Stick 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 every day or two, especially if we're experiencing a dry spell. Aim for about an inch of water per week. Water at the base of the plants to avoid wetting the leaves, which can encourage disease in our low-to-moderate humidity.

If the leaves start to yellow or droop, you're likely overwatering. If they look wilted and the soil is dry to the touch, they need more water. A light layer of mulch, like straw or grass clippings, can help retain moisture and keep the soil cool during those hot summer months.

You can expect your first harvest of green onions starting in late May and continuing all the way through late October. They're usually ready to harvest about 60 days after planting, when the stalks are about pencil-thick.

You can either pull up the entire plant or cut the stalks off above the base. If you cut them, they'll often regrow for another harvest. For a continuous supply, harvest only what you need and leave the rest to keep growing.

As our first frost approaches around mid- October, harvest any remaining green onions. You can chop and freeze them for use in soups and stews throughout the winter.

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

Onion Maggots

• What it looks like: Wilting plants, yellowing leaves, and small white maggots feeding on the roots.
• What causes it: Flies lay eggs at the base of the plants, and the maggots burrow into the bulbs.
• How to fix/prevent it: Use row covers to prevent flies from laying eggs. Apply beneficial nematodes to the soil.

Thrips

• What it looks like: Silver streaks on the leaves, distorted growth, and tiny, slender insects.
• What causes it: Thrips suck the sap from the leaves, causing damage.
• How to fix/prevent it: Spray plants with 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.
• 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, plants are stunted, and leaves may yellow.
• What causes it: A soilborne fungus that thrives in warm, wet conditions.
• How to fix/prevent it: Improve soil drainage. Rotate crops. Plant resistant varieties.

Great Plains Specific Challenges: Our extreme temperature swings and variable rainfall can stress green onions, making them more susceptible to pests and diseases. Consistent watering and good soil drainage are key to keeping them healthy. Hot, dry winds can also dry out the soil quickly, so mulching is essential.

Green onions are great companions for many plants in the Plains garden. Carrots benefit because the onion scent deters carrot root flies. Lettuce thrives in the partial shade provided by green onions, especially during our hot summers. Tomatoes and peppers are protected from some pests, and beets enjoy the improved soil conditions.

Avoid planting green onions near beans and peas, as they can inhibit their growth.