Arugula in Zone 5A — Great Plains

Arugula offers a peppery zest that really brightens up salads and sandwiches, and it's surprisingly easy to grow here in the Plains. Its quick growth cycle means you can get multiple harvests, even with our shorter growing season, and the flavor is so much better than what you find in the grocery store.

While we face extreme temperature swings and the occasional hail risk, arugula's fast maturity and tolerance for cooler weather make it a manageable and rewarding crop. With our 168-day growing season, you can easily squeeze in several plantings for a continuous supply.

Starting arugula indoors is definitely an option, especially if you're itching to get a head start. It's most useful for getting an early spring crop going strong.

Start your seeds indoors mid-March through early April, about three weeks before you plan to transplant. Use seed trays with a good seed-starting mix, provide warmth (a heat mat helps), and ensure plenty of light with grow lights. Bottom watering is a great way to keep the soil consistently moist without disturbing the delicate seedlings. Just set the tray in a shallow dish of water and let the soil soak it up. Our variable spring weather can be hard on young plants, so this gives them a protected start.

Transplanting arugula is a good way to get a jump on the season, especially after a late frost.

Harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Transplant outdoors mid-April through late May, spacing plants about 6 inches apart. Keep an eye on the forecast – a late frost can still happen, so be ready to cover your seedlings if needed.

Direct sowing arugula is the easiest and most common method, and it works well throughout the growing season.

Sow seeds directly into well-prepared soil from late March through mid-August. Arugula germinates best in cooler soil temperatures. Space seeds about 6 inches apart. Because it's so fast-growing, you can get a quick harvest this way. Just be aware that it bolts in the heat, so focus on spring and fall plantings for the best results.

Arugula needs consistent moisture to thrive, but overwatering can be just as bad as underwatering, especially with our heavy prairie soil.

During the spring and fall, when temperatures are cooler and rainfall is more frequent, you might only need to water once or twice a week. In the heat of summer, though, you'll likely need to water every other day, or even daily, especially if it hasn't rained. The "finger test" is your best guide: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week, either from rainfall or irrigation.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our low-to-moderate humidity. Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot.

A layer of mulch, like straw or shredded leaves, helps retain moisture in the soil and keeps the roots cool, which is particularly important during our hot summers.

You can expect your first harvest of arugula about 40 days after planting, which means early May for spring plantings and continuing through mid-October.

Harvest the young leaves when they're about 2-3 inches long for a milder flavor. Larger leaves will have a more pronounced peppery taste. Pick the leaves regularly, but before the plant starts to flower. Once it flowers, the leaves become bitter.

Harvest by snipping off the outer leaves, leaving the inner ones to continue growing. This encourages continuous production throughout the season. As the first frost approaches in early October, harvest any remaining leaves and consider succession planting indoors to extend your harvest.

Arugula is generally easy to grow, but here are some common problems we face in the Great Plains:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in leaves. You'll see small, dark beetles that jump when disturbed. The worst damage happens to young seedlings.
• What causes it: These small jumping beetles feed on the leaves. They're most damaging to small, young plants.
• How to fix/prevent it: Row covers are essential to protect seedlings during their vulnerable stage. Delay planting until plants are larger. A coating of kaolin clay can deter them. Neem oil spray also helps. Interplant arugula with basil or catnip. Healthy, vigorous plants often outgrow the damage.

Bolting in Heat

• What it looks like: The cool-season crop sends up a flower stalk when temperatures rise. The leaves become tough and bitter, and the harvest quality declines.
• What causes it: Extended warm temperatures above the crop's comfort zone. Arugula bolts when days consistently exceed 80°F.
• How to fix/prevent it: Time your plantings for cool weather in the spring and fall. Choose bolt-resistant varieties if available. Provide shade during warm spells. Mulch helps keep the soil cool. Harvest leaves frequently before bolting progresses too far.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. You might also see a sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may "farm" them for honeydew.
• How to fix/prevent it: A strong water spray can knock them off. Encourage ladybugs and lacewings, which are natural predators. Insecticidal soap is effective for heavy infestations, and neem oil works systemically. Avoid excess nitrogen fertilizer, as it attracts them.

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on the undersides. Leaves will brown and die from the bottom up.
• What causes it: An oomycete pathogen that spreads in cool, humid conditions via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around the plants. Water at the base, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties where available.

Great Plains Specific Challenges: Our hot summers, low-to-moderate humidity, and variable rainfall can stress arugula, making it more susceptible to bolting and flea beetles. Consistent watering is key, but be careful not to overwater in our heavy soil. Wind protection is also helpful to prevent damage to the delicate leaves.

Arugula benefits from several companion plants. Lettuce and spinach provide ground cover, helping to retain moisture and suppress weeds. Carrots and beets loosen the soil, improving drainage and root growth. Onions deter pests like aphids.

Avoid planting arugula near strawberries. Strawberries attract slugs, which can also damage arugula leaves.