Arugula in Zone 7A — Desert Southwest

Arugula is a fantastic addition to any Desert Southwest garden. Its peppery bite adds zing to salads, pizzas, and sandwiches, and it’s incredibly satisfying to harvest fresh greens from your own backyard, especially during our mild winters and extended fall. Plus, it's fast-growing, so you can enjoy multiple harvests in our two growing seasons.

We know the Desert Southwest presents unique challenges like extreme heat and alkaline soil, but with careful timing and a few tricks, you can absolutely grow delicious arugula. Our 230-day growing season offers plenty of opportunities to enjoy this cool-season crop. You just need to plan for summer survival.

Starting arugula indoors is an option, but generally not necessary in our climate, given its fast growth and preference for cooler temperatures. However, if you want a very early start, aim for mid-February through early March, about three weeks before you'd like to transplant.

Use seed trays filled with a good seed-starting mix, keep them warm, and provide plenty of light (a grow light works wonders). Bottom watering is great for seedlings; just set the tray in a shallow dish of water until the surface of the soil is moist. Remember, spring comes early here!

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

Space the seedlings about 6 inches apart in a well-prepared bed. Keep an eye on the forecast; unexpected late frosts can happen, so be ready to cover your plants if needed.

Direct sowing arugula is the easiest method, and it works well in our Desert Southwest climate. You can direct sow from late February through mid September, taking advantage of both our spring and fall growing seasons.

Prepare your soil by loosening it and adding compost. Arugula prefers soil temperatures between 45°F and 65°F for optimal germination. Sow seeds about ¼ inch deep and 6 inches apart. Remember, arugula bolts quickly in the heat, so focus on planting during cooler periods.

Arugula needs consistent moisture to thrive, but it doesn't like to be waterlogged. In our arid Desert Southwest climate, watering correctly is crucial for summer survival.

During the cooler spring and fall months, aim to water deeply about 2-3 times per week, providing about 1 inch of water each time. Use the finger test: if the top 2 inches of soil feel dry, it's time to water. During the monsoon season, let natural rainfall supplement your watering schedule, but be prepared to irrigate if the rains are sparse.

In the extreme heat of summer, you might need to water daily, especially if your arugula is in containers. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our arid environment. Signs of underwatering include wilting and slow growth; overwatering can lead to yellowing leaves and root rot. A layer of organic mulch, like 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 early April through mid November in our region. Harvest young leaves when they are 2-3 inches long for a milder flavor; larger leaves will have a more pronounced peppery taste.

To harvest, simply snip off the outer leaves with scissors, leaving the inner leaves to continue growing. This encourages continuous production. To extend your harvest into the cooler months, consider using row covers to protect against frost. If frost threatens in late October or early November, harvest what you can before it hits.

Here are some common problems you might encounter with arugula in the Desert Southwest, and how to tackle 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 that jump when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They thrive in dry conditions, making them common in our desert climate.
• How to fix/prevent it: Use row covers to protect seedlings. Delay planting until plants are larger and more resilient. Consider a kaolin clay coating or neem oil spray. Interplant with basil or catnip. Healthy, vigorous plants outgrow minor 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: Extended warm temperatures. Arugula is a cool-season crop and bolts when days consistently exceed 80°F, which is common here.
• How to fix/prevent it: Time your plantings for cool weather (spring and fall). Choose bolt-resistant varieties. Provide shade with shade cloth during warm spells. Mulch to keep the soil cool. Harvest frequently before bolting progresses.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects that thrive in warm weather.
• How to fix/prevent it: Strong water spray to knock them off. Encourage ladybugs and lacewings. Use insecticidal soap or neem oil for heavy infestations. Avoid excess nitrogen fertilizer, which attracts them.

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 by spacing plants adequately. Water at the base, never overhead. Copper-based fungicides can help prevent it. Plant resistant varieties if available.

Desert Southwest Specific Challenges: The extreme heat of our summers makes bolting a constant concern, so timing is everything. Low humidity can reduce disease pressure, but also means you need to be diligent about watering. Monsoon moisture can create brief periods of higher humidity, so watch out for fungal issues during those times.

Good companions for arugula include lettuce and spinach, as they share similar growing requirements and don't compete for nutrients. Carrots and beets are also beneficial because they help loosen the soil, improving drainage. Onions can deter some pests that might bother arugula. Avoid planting arugula near strawberries, as they can attract aphids, which can then spread to your arugula.