Green Onions in Zone 7A — Desert Southwest

Green onions are a fantastic addition to any Desert Southwest garden. Their mild, fresh flavor elevates everything from salsas to stir-fries, and they're incredibly easy to grow in our climate. Plus, the satisfaction of snipping fresh greens just steps from your kitchen is hard to beat.

Sure, our extreme heat and alkaline soil present challenges, but with smart timing and a little extra care, you can enjoy a continuous supply of green onions throughout our long, 230-day growing season. We can take advantage of our two growing seasons, planting in both spring and fall!

If you prefer to start your green onions indoors or purchase seedlings, aim to transplant them outdoors from late February through late March. This gives them a head start before the extreme heat hits.

Before planting, harden off your seedlings by gradually exposing them to the outdoor elements for about a week. This prevents shock and ensures they adapt well to the desert sun.

When transplanting, space them 2-3 inches apart in well-draining soil. Be mindful of late season temperature swings and protect young transplants from unexpected cold snaps with row covers if needed.

Direct sowing is the easiest way to grow green onions here in the Desert Southwest. You can sow seeds directly into your garden beds from late February through late August. That's right, almost year-round!

Prepare your soil by loosening it and amending with compost to improve drainage and fertility. Green onions prefer soil temperatures between 60-70°F for optimal germination. Sow seeds about ½ inch deep and 2-3 inches apart. You can also plant the root ends of store-bought green onions directly into the soil for a quick and easy start.

Green onions need consistent moisture to thrive, especially in our arid Desert Southwest climate. They aren't drought-tolerant and will quickly suffer in dry conditions.

During the spring and fall, when temperatures are milder, water deeply 2-3 times per week, providing about 1 inch of water each time. In the extreme heat of summer, increase watering to every other day, or even daily, to prevent the soil from drying out completely. The monsoon season can provide some relief, but don't rely solely on rainfall. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water.

Water at the base of the plants to avoid wetting the foliage, as this can encourage fungal diseases in our climate. Wilting or yellowing leaves can indicate underwatering, while soggy soil and stunted growth can signal overwatering. A light layer of mulch, like straw or shredded leaves, can help retain moisture and regulate soil temperature.

You can expect your first harvest of green onions from late April through mid November, about 60-70 days after planting. Look for stalks that are at least pencil-thick.

To harvest, you can either pull the entire plant from the ground or snip the green tops off about an inch above the soil line. If you cut them, the plants will regrow, providing you with multiple harvests. For continuous production, stagger your plantings every few weeks.

As the first frost approaches in early November, harvest any remaining green onions to enjoy fresh or preserve for later use. You can also pot up a few plants and bring them indoors to extend your harvest through the winter.

Here are some common problems you might encounter with green onions in the Desert Southwest:

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 and can be particularly problematic in the spring.
• How to fix/prevent it: Use row covers to prevent adult flies from laying eggs near your plants. Remove and destroy any infested plants. Introduce beneficial nematodes to the soil to control the maggots.

Thrips

• What it looks like: Small, slender insects that feed on the leaves, causing silvery streaks and distorted growth.
• What causes it: Thrips thrive in hot, dry conditions, making them a common pest in our region.
• How to fix/prevent it: Regularly spray plants with a strong jet of water to dislodge thrips. Insecticidal soap or neem oil can also be effective. Encourage beneficial insects like ladybugs and lacewings, which prey on thrips.

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.

Pink Root

• What it looks like: Roots turn pink or reddish, causing stunted growth and reduced yields.
• What causes it: A soilborne fungus that is more prevalent in warm, alkaline soils.
• How to fix/prevent it: Improve soil drainage and avoid overwatering. Rotate crops to prevent the fungus from building up in the soil. Solarize the soil during the hottest months to kill the fungus.

Desert Southwest Specific Challenges: The extreme heat of our summers can stress green onions, making them more susceptible to pests and diseases. The arid humidity means we have to be vigilant about watering, while the occasional monsoon moisture can create conditions favorable for fungal diseases. Choosing heat-tolerant varieties and providing afternoon shade can help mitigate these challenges.

Companion planting can be a great way to improve the health and productivity of your green onions. Carrots are excellent companions because their scent deters onion flies. Lettuce provides ground cover, helping to retain moisture and suppress weeds.

Tomatoes and peppers also benefit from being planted near green onions, as the onions can help repel certain pests. Beets are also good companions, as they don't compete for the same nutrients in the soil. Avoid planting green onions near beans or peas, as they can inhibit each other's growth.