Arugula in Zone 6B — Great Plains

Arugula delivers a spicy, peppery kick that really brightens up salads and sandwiches, and it's one of the quickest crops you can grow in your Great Plains garden. Its flavor is especially welcome when the intense summer heat is making other greens a bit bland. Plus, it's incredibly satisfying to harvest fresh greens just weeks after planting, even with our variable spring weather.

Our region definitely throws some curveballs – wind, temperature swings, and the risk of hail can be tough on tender greens. But with careful timing and a few smart strategies, you can easily enjoy multiple harvests of arugula throughout our 198-day growing season.

Starting arugula indoors is possible, especially if you're itching to get a head start in late February through mid March. This is about 3 weeks before you'd want to transplant outdoors. Use seed trays with a good seed-starting mix, provide warmth (a heat mat helps), and ensure plenty of light, either from a grow light or a very sunny window.

A good tip is to water from the bottom to prevent damping off. Set your seed trays in a shallow tray of water and let the soil soak it up. This keeps the leaves dry and happy. Honestly, direct sowing usually works great for arugula, but starting indoors can give you a jump on the season if you're eager to get your first harvest extra early, given how variable our springs can be.

Transplanting arugula seedlings outdoors should happen late March through early May. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature fluctuations common in the Plains.

Space your plants about 6 inches apart in a spot with full sun to partial shade. Keep an eye on the forecast – a late frost can still happen, so be ready to cover your seedlings if needed.

Direct sowing is the easiest way to grow arugula in our region, especially since it germinates quickly. You can sow seeds mid March through early September. Just make sure the soil temperature is at least 40°F.

Prepare your soil by loosening it and removing any rocks or debris. Sow seeds about ¼ inch deep and 6 inches apart. Keep the soil consistently moist. Arugula is fast-growing, but it bolts quickly in the heat, so focus on planting in cooler weather for the best results.

Arugula needs consistent moisture to thrive, but avoid soggy soil. In the Great Plains, where we often experience variable rainfall and periods of drought, this can be a bit of a balancing act. During the spring and fall, when temperatures are cooler, aim for about 1 inch of water per week, either from rainfall or irrigation.

The "finger test" is your best friend: stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. In the heat of summer, you might need to water more frequently, especially if rainfall is scarce. 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 a very strong, bitter flavor. Overwatering can lead to yellowing leaves and root rot. Applying a layer of mulch, like straw or shredded leaves, can help retain soil moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

You can expect your first harvest of arugula late April through early November, about 40 days after planting. The best time to harvest is when the leaves are young and tender, about 2-3 inches long. At this size, they have a milder flavor. As the leaves mature, they become more peppery.

To harvest, simply snip off the outer leaves with scissors or a knife, leaving the inner leaves to continue growing. This encourages continuous production. Keep harvesting regularly to prevent the plant from bolting (going to seed).

As the first frost approaches in late October, harvest any remaining leaves. Arugula can tolerate a light frost, but a hard freeze will kill it. You can also cover your plants with a frost blanket to extend the harvest a bit longer.

Here are some common problems you might encounter growing arugula in the Great Plains:

Flea Beetles

• What it looks like: Tiny round holes (shot-hole pattern) in the leaves, especially on young seedlings. You might also see small, dark beetles that jump 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 during their vulnerable stage. You can also delay planting until plants are larger and more resilient. A coating of kaolin clay can deter them. Neem oil spray can also help. Interplant with basil or catnip. Healthy, vigorous 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. Harvest quality declines.
• What causes it: Extended warm temperatures above the plant's comfort zone. In our region, this often happens quickly with our extreme temperature swings.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells using shade cloth. Mulch to 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. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations explode 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 also works. 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: 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 by spacing plants properly. Water at the base, never overhead. Copper-based fungicides can help prevent it. Plant resistant varieties if available.

Great Plains Specific Challenges: Our region's hot summers and variable rainfall can make it challenging to keep arugula consistently moist without encouraging bolting or disease. Wind protection is also essential to prevent damage to the tender leaves. Keep a close eye on the weather forecast and adjust your watering and shading strategies accordingly.

Arugula benefits from companion planting. Lettuce and spinach are good companions because they have similar growing requirements and can provide shade for each other, which is helpful in our hot summers. Carrots and beets are also good choices because they don't compete for the same nutrients and can help loosen the soil, improving drainage. Onions can help deter pests like aphids.

Avoid planting arugula near strawberries. Strawberries are susceptible to verticillium wilt, which can also affect arugula. Keeping them separated reduces the risk of disease spread.