Arugula in Zone 7B — Desert Southwest

Arugula, with its peppery bite, is a fantastic addition to any Desert Southwest garden. It’s quick to mature, versatile in salads and cooked dishes, and offers the satisfaction of fresh greens even during our shorter growing windows. Plus, a sprinkle of monsoon moisture can really enhance its flavor.

Desert gardening presents challenges like extreme heat and alkaline soil, but arugula's fast growth cycle allows you to harvest before the worst of the summer heat hits. With our long 245-day growing season and two distinct planting windows, you can enjoy arugula for much of the year with careful timing.

Starting arugula indoors is an option, but honestly, it's so quick to grow from seed that direct sowing is often easier in our climate. If you want a very early start, sow seeds indoors from early to late February, about three weeks before you plan to transplant. Use seed trays with a good seed-starting mix, keep them warm, and provide plenty of light.

Bottom watering is a great way to keep the soil evenly moist without damping off. Because our spring comes on very-early here, you'll want to keep a close eye on soil temps, and transplant as soon as you have true leaves.

Transplant your arugula seedlings outdoors from early March through mid April. Before transplanting, harden them off by gradually exposing them to outdoor conditions for about a week. This prevents transplant shock.

Space the seedlings about 6 inches apart. Keep an eye on the weather forecast – a late frost can still happen, even in our mild winters. Cover your seedlings if a freeze is predicted.

Direct sowing arugula is the most common and easiest method for Desert Southwest gardeners. Sow seeds from mid February through late September for a continuous harvest.

Prepare your soil by loosening it and mixing in some compost. Arugula prefers cooler soil, so avoid sowing during the hottest part of the day. Plant seeds about ¼ inch deep and 6 inches apart. Keep the soil consistently moist until germination.

Arugula needs consistent moisture, especially in our arid Desert Southwest climate. While it's not drought-tolerant, the amount of watering you provide can affect the flavor.

During the spring and fall growing seasons, aim for about 1 inch of water per week. Use the "finger test" – stick your finger about 2 inches into the soil. If it feels dry, it's time to water. In the hotter months, you may need to water more frequently, especially during our monsoon season when humidity spikes. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases.

Signs of underwatering include wilting and yellowing leaves. Overwatering can lead to root rot, indicated by soggy soil and stunted growth. Mulching around your arugula plants with straw or wood chips can help retain moisture and keep the soil cool.

You can expect your first arugula harvest about 40 days after planting, typically from late March through late November in our region. The leaves are ready to harvest when they are about 2-3 inches long.

For a milder flavor, harvest younger leaves. Larger leaves will have a more pronounced peppery taste. Harvest by snipping off the outer leaves, leaving the inner ones to continue growing. This encourages continuous production.

As the first frost approaches in mid- November, harvest any remaining arugula leaves. You can also cover the plants with a frost blanket to extend the harvest a bit longer, but don’t expect it to last much into winter.

Arugula, like all plants, can face challenges in the Desert Southwest. Here are some common problems and how to deal with them:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves, especially on young seedlings. You might see small, dark beetles jumping when disturbed.
• What causes it: These small jumping beetles feed on the leaves. They are most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger. Kaolin clay coating can deter them. Neem oil spray can help. Interplant with basil or catnip. Healthy plants often outgrow the damage.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: Arugula is a cool-season crop and bolts when temperatures rise consistently above its comfort zone.
• How to fix/prevent it: Time your plantings for cool weather (spring and fall). Choose bolt-resistant varieties. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest frequently to delay bolting.

Aphids

• What it looks like: Clusters of tiny insects (green, black, or white) on stems and leaf undersides. You may see sticky honeydew and curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that reproduce rapidly, especially in warm weather.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations. Neem oil can also help. Avoid excess nitrogen fertilizer.

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: This fungal disease spreads in cool, humid conditions.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation. Water at the base, never overhead. Copper-based fungicides can help prevent it. Plant resistant varieties if available.

Desert Southwest Specific Challenges: Our extreme heat can cause bolting, so shade cloth is essential for summer survival. Low humidity reduces the risk of some fungal diseases, but monsoon rainfall can create temporary humid conditions that favor downy mildew. Alkaline soil can impact nutrient availability, so amend with compost regularly.

Companion planting can benefit your arugula in the Desert Southwest. Plant arugula near lettuce and spinach, as they have similar growing requirements and can provide mutual shade. Carrots and beets are also good companions, as they don't compete for the same nutrients. Onions can help deter pests. Avoid planting arugula near strawberries, as they can attract similar pests and diseases.