Arugula in Zone 6A — Midwest

Arugula is a fantastic addition to any Midwest garden. Its peppery bite adds a unique flavor to salads, sandwiches, and pizzas, and it thrives in our fertile soil. Plus, it's incredibly rewarding to harvest fresh greens just weeks after planting, especially in early spring when we're all craving fresh produce after a long winter.

Our Midwest weather can be unpredictable, with variable springs and summer heat spells, but arugula's quick growth cycle makes it manageable. You can easily sneak in multiple plantings throughout our 178-day growing season, taking advantage of the cooler periods for optimal growth.

Starting arugula indoors is possible, but honestly, direct sowing is usually the way to go here in the Midwest. However, if you're eager for an extra-early start, you can sow seeds indoors from early to late March, about 3 weeks before you plan to transplant.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist (bottom watering helps prevent damping off) and provide plenty of light, either with a grow light or a sunny windowsill. Given our moderate-to-late spring character, this can give you a head start, but watch the weather closely before transplanting.

Transplanting arugula outdoors can begin from early April through mid May, as soon as the soil is workable. Before transplanting, be sure to harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space the plants about 6 inches apart in well-drained soil. Keep an eye on the weather forecast – a late frost can still happen in the Midwest, so be prepared to cover your seedlings if necessary.

Direct sowing arugula is the easiest and most common method for Midwest gardeners. You can sow seeds directly into the garden from late March through late August, allowing for multiple harvests throughout the growing season.

Prepare the soil by loosening it and removing any rocks or debris. Sow seeds about ¼ inch deep and 6 inches apart. Arugula is fast-growing and germinates quickly in cool soil, but it also bolts in the heat, so focus on planting during cooler periods.

Arugula needs consistent moisture to thrive, but it's crucial to find the right balance, especially with our Midwest climate. During the spring and fall, when temperatures are cooler and rainfall is more frequent, you may only need to water once or twice a week, depending on rainfall.

The finger test is your best friend: stick your finger about 2 inches into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation. During the summer heat, you'll likely need to water more frequently, perhaps every other day, especially during any summer heat spells.

With our moderate-to-humid conditions, it's best to water at the base of the plants to avoid getting the leaves wet, which can encourage fungal diseases. Signs of underwatering include wilting leaves and slow growth. Overwatering, on the other hand, can lead to root rot. A layer of mulch, like straw or shredded leaves, will help retain moisture and keep the soil cool.

You can expect your first arugula harvest from early May through late October, about 40 days after planting. The best time to harvest is when the leaves are young and tender, about 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, leaving the inner ones to continue growing. This encourages continuous production throughout the season. Be sure to harvest before the plants start to flower, as bolting will make the leaves bitter.

As our first frost approaches in mid- October, harvest any remaining leaves to enjoy a final taste of fresh arugula before winter sets in. You can also cover the plants with a frost blanket for a little extra protection and a few more harvests.

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

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: Flea beetles are small jumping beetles that feed on the leaves. They are most damaging to small, young plants and can be a real nuisance in the spring.
• How to fix/prevent it: Row covers are your best defense to protect seedlings during their vulnerable stage. You can also delay planting until plants are larger. Kaolin clay coating can deter them, and neem oil spray is another option. Interplanting with basil or catnip can also help.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter. Harvest quality declines rapidly.
• What causes it: Bolting is triggered by extended warm temperatures, which are common during our Midwest summer heat spells.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties if possible. Provide shade during warm spells with shade cloth or by planting in a partially shaded location. Mulch to keep the soil cool. Harvest frequently to delay bolting.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue and curled or distorted new growth are also signs.
• What causes it: Aphids are sap-sucking insects that reproduce rapidly, especially in warm weather.
• How to fix/prevent it: A strong water spray can knock them off the plants. Encourage ladybugs and lacewings, which are natural predators. Insecticidal soap can be used 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 the upper leaf surface with fuzzy gray-purple growth on the undersides. Leaves turn brown and die from the bottom up.
• What causes it: Downy mildew is a disease 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 of the plants, never overhead. Copper-based fungicides can be used for prevention.

Midwest Specific Challenges: Our moderate-to-hot summers, moderate-to-humid humidity, and wet-summer rainfall create conditions that can exacerbate bolting, aphid infestations, and downy mildew. Pay close attention to watering practices and air circulation to minimize these issues.

Arugula benefits from companion planting. Lettuce and spinach are good companions because they share similar growing requirements and don't compete for resources. Carrots and beets help loosen the soil, making it easier for arugula roots to grow, plus they don't take up much space above ground. Onions deter pests like aphids, protecting your arugula.

Avoid planting arugula near strawberries. Strawberries are susceptible to verticillium wilt, which can also affect arugula, so it's best to keep them separated to prevent the spread of disease.