Arugula in Zone 4B — Great Plains

Arugula is a fantastic addition to any Plains garden. Its peppery bite adds zest to salads, sandwiches, and pizzas, and it thrives in our cool spring and fall weather. Plus, there's real satisfaction in harvesting fresh greens just weeks after planting.

Our region's extreme temperature swings and potential for drought can be tough on many crops, but arugula is quick and relatively forgiving. With a 149-day growing season, you have plenty of time to get multiple harvests of this leafy green.

Starting arugula indoors is definitely an option, especially if you want a head start in our shorter growing season, or if you're dealing with a particularly windy spring. Starting indoors gives the young plants a chance to get established before facing the elements.

You can start seeds indoors from late March through mid April, about 3 weeks before you plan to transplant them outside. Use seed trays or small pots with a good seed-starting mix. Keep them warm and provide plenty of light – a grow light works wonders. Don't forget to water from the bottom to encourage strong root growth. Given our variable spring weather, this can be a good way to get things going even if the weather outside is less than ideal.

Transplanting arugula seedlings outdoors should be done from late April through early June. This timing allows you to avoid the worst of the late frosts while still giving the plants plenty of time to mature before the summer heat sets in.

Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Space them about 6 inches apart in a well-prepared garden bed. Keep an eye on the forecast – a late spring cold snap can still happen, so be ready to cover them if needed.

Direct sowing arugula is the easiest way to grow it, and it works well in our climate as long as you time it right. You can direct sow from early April through early August, taking advantage of the cooler parts of the growing season.

Prepare your soil by loosening it and removing any rocks or debris. Sow the seeds about ¼ inch deep and 6 inches apart. Arugula seeds germinate best in cool soil, so keep the soil consistently moist until they sprout. The downside of direct sowing is that young seedlings can be vulnerable to flea beetles, so keep a close eye on them.

Arugula needs consistent moisture to thrive, but it doesn't like to be waterlogged. Finding the right balance is key, especially in our variable Plains climate.

During the spring and fall, when temperatures are cooler and rainfall is more likely, you might only need to water once or twice a week, depending on rainfall. But during the hotter summer months, you may need to water every day or every other day, especially if you're dealing with drought conditions. Stick your finger about 2 inches into the soil – if it feels dry, it's time to water. Aim for about an inch of water per week, whether it comes from rain or your hose.

Water at the base of the plants to avoid wetting the leaves, which can increase the risk of fungal diseases in our low-to-moderate humidity. Yellowing leaves can indicate overwatering, while wilting or stunted growth can mean underwatering. A layer of mulch can help retain soil moisture and regulate soil temperature, which is especially helpful during our extreme temperature swings.

You can expect your first arugula harvest about 40 days after planting, so from mid May through early October, depending on when you planted. Look for leaves that are 2-3 inches long for a milder flavor. Larger leaves will have a more pronounced peppery taste.

Harvest by snipping off the outer leaves, leaving the inner leaves to continue growing. This cut-and-come-again method will give you a continuous harvest throughout the season. As the first frost approaches in early October, harvest any remaining leaves to enjoy before the cold weather sets in.

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 see small, dark beetles jumping when disturbed.
• What causes it: Small jumping beetles that feed on leaves. They are most damaging to small, young plants.
• How to fix/prevent it: Use row covers to protect seedlings during their vulnerable stage. Delay planting until plants are larger and more resilient. Kaolin clay coating can deter them. Neem oil spray can also help. Interplant with basil or catnip to confuse the beetles. Healthy, vigorous plants tend to 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 rapidly.
• What causes it: Extended warm temperatures, especially when days consistently exceed 80°F. This is common in our Plains summers.
• How to fix/prevent it: Time your plantings for cooler weather in spring and fall. Choose bolt-resistant varieties if available. Provide shade during warm spells with shade cloth. Mulch to keep the soil cool. Harvest frequently to encourage continued leaf production before bolting progresses.

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 can explode in warm weather.
• How to fix/prevent it: A strong water spray can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap can be used for heavy infestations. 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 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 if available.

Great Plains Specific Challenges: The hot summers in the Plains can quickly cause arugula to bolt, so focus on spring and fall plantings. Our variable rainfall means you need to monitor soil moisture closely and adjust watering accordingly. The wind can also dry out the soil quickly, so mulching is essential.

Arugula benefits from companion planting. Lettuce and spinach make good neighbors because they have similar growing requirements and can provide shade to arugula during hot spells. Carrots and beets are also good companions because they don't compete for the same nutrients and can help loosen the soil. Onions deter pests like aphids, which can be a problem for 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.