Green Onions in Zone 7B — Desert Southwest

Green onions are a must-grow for any Desert Southwest gardener. Their mild, fresh flavor elevates everything from salsas to grilled meats, and they're incredibly versatile in the kitchen. Plus, there's nothing quite like the satisfaction of snipping fresh green onions from your own garden, especially in a climate where truly fresh produce can be a challenge.

Don't let our extreme heat scare you off! With our long 245-day growing season and two distinct planting windows, you can easily grow green onions here. Timing is key, and with a little attention to watering, you'll be enjoying homegrown green onions in no time.

You can transplant green onion starts into your garden beds from mid February through mid March. This gives them a head start before the intense summer heat arrives. Before planting, be sure to harden off your seedlings by gradually exposing them to the outdoor conditions for about a week.

When transplanting, space the seedlings 2-3 inches apart. Keep an eye on the weather forecast, as this time of year can bring unexpected temperature swings. Protect young transplants from late frosts with row covers if needed.

Direct sowing is the easiest way to grow green onions in our climate, and it gives you the most flexibility. Sow seeds directly into well-prepared garden beds from mid February through early September. Green onion seeds germinate best when the soil temperature is between 60°F and 70°F.

Prepare your soil by loosening it and amending with compost to improve drainage and fertility. Plant seeds about ½ inch deep and 2-3 inches apart. You can also plant the root ends of store-bought green onions! Just stick the white root end into the soil, and watch them regrow.

Green onions need consistent moisture to thrive, but they don't like soggy soil. In our arid Desert Southwest climate, this means paying close attention to your watering schedule, especially during the hot summer months. During the spring and fall, water deeply about 2-3 times per week, providing about 1 inch of water each time. When the extreme heat hits, increase watering to every other day, or even daily, ensuring the soil stays consistently moist.

Use the "finger test" to check soil moisture: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Always water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases, especially during our monsoon season. Signs of underwatering include wilting and yellowing leaves, while overwatering can lead to root rot.

Mulching around your green onions with a layer of straw or wood chips helps retain moisture, keeps the soil cool, and suppresses weeds. Just be sure to keep the mulch a few inches away from the base of the plants to prevent rot.

You can expect your first harvest of green onions about 60-70 days after planting, typically from mid April through late November in our region. The ideal time to harvest is when the stalks are about pencil-thick. You can either pull the entire plant up, or snip the stalks off about an inch above the soil line.

If you cut above the base, the green onions will regrow, giving you multiple harvests from a single planting. For continuous production, plant new seeds every few weeks. As our first frost approaches in mid- November, harvest any remaining green onions to use fresh or freeze for later.

Here are some common problems you might encounter growing 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 a problem, especially in spring and fall.
• How to fix/prevent it: Use row covers to prevent adult flies from laying eggs near your plants. Beneficial nematodes can also help control maggots in the soil.

Thrips

• What it looks like: Silvery streaks or spots on the leaves, distorted growth, and tiny, slender insects visible on the plant.
• What causes it: Thrips thrive in hot, dry conditions, making them a common pest in our region.
• How to fix/prevent it: Provide consistent moisture, and spray plants with insecticidal soap or neem oil. Encourage beneficial insects like ladybugs and lacewings to feed 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. 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 is more prevalent in warm soils with high moisture.
• How to fix/prevent it: Improve soil drainage, practice crop rotation, and plant resistant varieties. Solarizing the soil can also help reduce the fungal population.

Desert Southwest Specific Challenges Our extreme heat can stress green onions, making them more susceptible to pests and diseases. Consistent watering is crucial to help them withstand the heat. The monsoon season can bring periods of high humidity, increasing the risk of fungal diseases like downy mildew. Alkaline soil can also be a challenge, so amend your soil with compost to improve its pH and nutrient content.

Companion planting can help your green onions thrive. Carrots are great companions because their scent deters onion flies, while green onions deter carrot flies. Lettuce and other leafy greens benefit from the shade provided by green onions, especially during the hottest part of the day. Tomatoes and peppers also benefit from the pest-repelling properties of green onions. Beets are good companions as they don't compete for the same nutrients. Avoid planting green onions near beans and peas, as they can inhibit each other's growth.