Green Onions in Zone 3A — Mountain West

Green onions are a fantastic addition to any Mountain West garden. Their mild, fresh flavor elevates everything from summer salads to grilled meats, and they're incredibly versatile in the kitchen. Plus, the satisfaction of snipping fresh green onions from your own garden is hard to beat, especially when they're so quick to mature in our intense sunlight.

We know high altitude gardening comes with challenges, like our short 96-day growing season and unpredictable weather. But with a little attention to timing, you can easily grow a continuous supply of green onions. You'll be harvesting flavorful stalks from early July through mid-September.

If you choose to start your green onions indoors, aim to transplant them outdoors from early May through early June, once the soil has warmed up a bit. Be sure to harden off your seedlings for about a week before transplanting. Gradually expose them to the elements to avoid shocking them.

Space your transplants about 2-3 inches apart. In early May, we can still get some chilly nights and even a late frost, so keep an eye on the forecast and be ready to cover your young plants if needed.

Direct sowing is the easiest way to grow green onions in our short season. Sow seeds directly into the garden from early May through late June. You can plant a new batch every few weeks for a continuous harvest.

Make sure the soil is loose and well-draining. Green onions prefer a soil temperature above 50°F for germination. Plant seeds about ½ inch deep and 2-3 inches apart. Keep the soil consistently moist until seedlings emerge. For an even easier start, try planting the root ends of store-bought green onions – just stick them in the ground and watch them grow!

Green onions need consistent moisture to thrive, but overwatering can lead to problems. In our dry Mountain climate, this can be a tricky balance. Aim to keep the soil consistently moist, but not soggy.

During the heat of summer, you'll likely need to water your green onions every 2-3 days. Use the "finger test" – stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. Give them about 1 inch of water per week, either from rainfall or irrigation. Water at the base of the plants to avoid wetting the foliage. This helps prevent fungal diseases in our low-humidity environment.

Wilting or yellowing leaves can indicate underwatering, while mushy or rotting stalks can signal overwatering. A light layer of mulch, like straw or shredded bark, can help retain moisture in the soil and regulate soil temperature, which is especially helpful with our intense sun.

You can expect your first harvest of green onions from early July through mid-September, about 60 days after planting. A good indicator is when the stalks are about pencil-thick. Don't wait too long, or they can become tough.

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, giving you multiple harvests. For continuous production, plant new seeds every few weeks.

As our first frost approaches in early September, harvest any remaining green onions. You can chop and freeze them for later use or transplant them into pots and bring them indoors to extend your harvest.

Here are some common problems you might encounter growing green onions in the Mountain West:

• 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 onions and related plants. They can be more prevalent during cool, wet springs.
• How to fix/prevent it: Use row covers to prevent the adult flies from laying eggs near your plants. Introduce beneficial nematodes to the soil.
• Thrips
• What it looks like: Silvery or white streaks on the leaves, distorted growth, and tiny black insects visible on the plant.
• What causes it: Thrips are tiny insects that suck the sap from plants. They thrive in hot, dry conditions, which we often experience in the summer.
• How to fix/prevent it: Encourage beneficial insects like ladybugs and lacewings. Spray plants with a strong stream of water to dislodge thrips. 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. Plant resistant varieties where available.
• Pink Root
• What it looks like: Pink or reddish roots, stunted growth, and yellowing leaves.
• What causes it: A soilborne fungus that infects the roots, especially in warm, dry soil. Alkaline soil can worsen the problem.
• How to fix/prevent it: Improve soil drainage. Rotate crops to avoid planting onions in the same spot year after year. Amend the soil with organic matter to improve its structure and nutrient content.

Mountain West Specific Challenges: Our intense sun can stress plants, making them more susceptible to pests and diseases. The low humidity helps reduce the risk of fungal diseases, but it also means we need to be extra vigilant about watering. Hail can also damage plants, so consider using row covers or other protective measures during severe weather.

Companion planting can be a great way to improve the health and yield of your green onions. Carrots are good companions because they deter onion flies. Lettuce provides ground cover, helping to keep the soil cool and moist. Tomatoes and peppers benefit from the onion's pest-repelling properties. Beets also make good companions, as they don't compete for the same nutrients.

Avoid planting green onions near beans and peas. These legumes can inhibit the growth of onions, as they prefer different soil conditions.