Green Onions in Zone 6B — Great Plains

Green onions are a must-grow for any Plains gardener. Their fresh, mild flavor elevates everything from grilled burgers to summer salads, and they're so easy to snip right from the garden as you need them. Plus, the satisfaction of growing your own onions, even these little guys, in our prairie soil is hard to beat.

Our region's extreme weather can be a challenge, with temperature swings and the occasional hail risk, but green onions are fast-growing and relatively unfussy. With a 198-day growing season, you have plenty of time to get multiple harvests.

You can transplant green onion seedlings outdoors from mid-March through early April. Before planting, be sure to harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Plains' intense sunshine and variable temperatures.

When transplanting, space the seedlings 2-3 inches apart. Keep an eye on the forecast, as late frosts are possible. If a cold snap threatens, cover your transplants with row covers or blankets for protection.

Direct sowing is the easiest way to grow green onions here. Sow seeds from mid-March through mid-August for a continuous harvest. Green onions don't mind the heat as long as they have consistent moisture.

Prepare your soil by loosening it and adding compost. Plant seeds about ½ inch deep, spacing them 2-3 inches apart. Keep the soil consistently moist until the seedlings emerge. For a super easy start, you can also plant the root ends of store-bought green onions in the soil. They'll readily sprout new growth.

Consistent moisture is key for tender, mild green onions. They aren't drought-tolerant and their shallow roots dry out quickly, especially during our hot Plains summers. But you also don't want soggy soil, which can lead to problems.

During the spring and fall, when temperatures are milder and rainfall is more frequent (if we're lucky!), aim for about 1 inch of water per week. In the heat of summer, increase that to 1.5-2 inches, depending on rainfall. Check the soil moisture by sticking your finger about 2 inches deep; if it feels dry, it's time to water. Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity.

Signs of underwatering include wilted or yellowing leaves. Overwatering can cause stunted growth and yellowing, especially at the base of the plant. A layer of mulch, like straw or shredded leaves, helps retain moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

You can expect your first harvest of green onions starting in mid-May, and you can continue harvesting well into early November. Green onions are ready to harvest when the stalks are about pencil-thick, typically 60-70 days after planting.

To harvest, you can either pull up the entire plant or cut the stalks about an inch above the base. If you cut them, they'll often regrow for a second harvest. Keep harvesting regularly to encourage continued production. As the first frost approaches in late October, harvest any remaining green onions to use fresh or preserve by freezing or drying.

Here are some common problems you might encounter with 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: Onion maggots are the larvae of a fly that lays its eggs near onion plants. They thrive in moist soil.
• How to fix/prevent it: Use row covers to prevent the flies from laying eggs. Remove and destroy any infested plants. Introduce beneficial nematodes to the soil.

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 plant sap. They are more common during hot, dry weather.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Spray plants with a strong stream of water or insecticidal soap.

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's growth is stunted.
• What causes it: A soilborne fungus that infects the roots, especially in warm, wet conditions.
• How to fix/prevent it: Improve soil drainage. Rotate crops to avoid planting onions in the same spot year after year. Plant resistant varieties if available.

Great Plains Specific Challenges: Our region's 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 and good soil drainage are key to keeping them healthy. Wind protection is essential.

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. Tomatoes and peppers can also be good companions, as green onions help deter pests that attack them. Beets also make good companions.

Avoid planting green onions near beans or peas. These legumes can inhibit onion growth.