Arugula in Zone 6B — Pacific Northwest

Arugula, with its peppery bite, thrives in our mild Pacific Northwest summers and cool nights. It's incredibly versatile – toss it in salads, add it to pizzas, or even blend it into pesto. Plus, there's nothing quite like the satisfaction of harvesting fresh greens from your own garden, especially when they're as easy to grow as arugula!

Our growing season here is around 162 days, and while we might struggle with heat-loving plants, arugula is perfectly suited for our climate. We might have overcast spring days and wet springs, but with a little planning, you can enjoy a continuous harvest of this delicious green.

Starting arugula indoors is definitely an option, especially if you're itching to get a jump start on the season. Aim to sow your seeds indoors from mid-March through early April, about three weeks before you plan to transplant. This will give your seedlings a head start before the soil warms up enough for direct sowing.

Use seed trays or small pots filled with a good seed-starting mix. Keep them warm and provide plenty of light – a grow light is ideal, especially with our often-overcast spring weather. Don't forget to water from the bottom to encourage strong root growth and prevent damping off.

Honestly, though, because arugula grows so quickly, you might find direct sowing just as effective, especially if you're short on indoor space.

Once the danger of hard frost has passed, usually from mid-April through late May, you can transplant your arugula seedlings outdoors. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

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

Direct sowing arugula is the easiest way to go for many of us in the PNW. Sow seeds directly into the garden from early April through mid-August for a continuous supply of fresh greens. Arugula germinates quickly, so you'll see seedlings popping up in no time.

Prepare your soil by loosening it and removing any rocks or debris. Sow the seeds about ¼ inch deep and 6 inches apart. Keep the soil consistently moist, especially during germination. The only real downside to direct sowing is that arugula bolts easily in the heat, so time your plantings accordingly to take advantage of our cool weather.

Arugula needs consistent moisture to thrive, but overwatering can lead to problems. During our wet springs, you might not need to water at all, but once the dry summer months arrive, you'll need to be more diligent.

A good rule of thumb is to check the soil moisture about 2 inches down – if it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or irrigation. Watering at the base of the plants is best, as overhead watering can encourage fungal diseases, especially if we get a spell of humid weather.

If your arugula leaves start to wilt or turn yellow, it's a sign of underwatering. On the other hand, if the leaves are swollen and the plants seem stunted, you might be overwatering. Mulching around your plants with straw or wood chips can help retain moisture and keep the soil cool during our mild summers.

You can expect your first arugula harvest about 40 days after planting, typically from mid-May through mid-October in our region. The leaves are ready to harvest when they're about 2-3 inches long. Smaller leaves will have a milder flavor, while larger leaves will be more peppery.

To harvest, simply snip off the outer leaves with scissors or garden shears, leaving the inner leaves to continue growing. This cut-and-come-again method will give you a continuous harvest throughout the season. Be sure to harvest before the plants start to flower, as the leaves will become bitter once they bolt.

As our first frost approaches in early October, harvest any remaining arugula leaves to enjoy before the cold weather sets in. You can also cover your plants with a frost blanket to extend the harvest a bit longer.

Arugula is relatively easy to grow, but you might encounter a few common problems:

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 jumping around when disturbed.
• What causes it: These small jumping beetles love to munch on arugula leaves. They're most active in spring when plants are small and vulnerable.
• How to fix/prevent it: Row covers are your best defense, especially for young seedlings. You can also try delaying planting until the plants are larger and better able to withstand the damage. Neem oil spray can also help, and interplanting with basil or catnip can deter them.

Bolting in Heat

• What it looks like: The plant sends up a flower stalk, and the leaves become tough and bitter.
• What causes it: Arugula is a cool-season crop, and it bolts (goes to seed) when temperatures rise. Extended warm temperatures above 80°F trigger bolting.
• How to fix/prevent it: Time your plantings for cool weather in spring and fall. Choose bolt-resistant varieties. Provide shade during warm spells, and mulch to keep the soil cool. Harvest frequently to encourage continued leaf production.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. You might also see a sticky honeydew residue and curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that thrive in warm weather.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage natural predators like ladybugs and lacewings. Insecticidal soap or neem oil can also be effective. Avoid over-fertilizing with nitrogen, as this attracts aphids.

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: This fungal disease spreads in cool, humid conditions.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation by spacing plants properly. Water at the base of the plants, and avoid overhead watering. Copper-based fungicides can help prevent the spread of the disease.

Pacific Northwest Specific Challenges: While we don't often get scorching heat, our springs can be cool and wet, which can encourage downy mildew. Keep an eye on your plants and take preventative measures to ensure a healthy harvest. Our mild summers are generally great for arugula, but be prepared to provide some shade during any unexpected heat waves to prevent bolting. And don't forget the slugs!

Arugula benefits from several companion plants. Lettuce and spinach are great neighbors, as they share similar growing conditions and don't compete for resources. Carrots and beets also make good companions, as their root systems help to loosen the soil and improve drainage. Onions can help repel pests like aphids.

Avoid planting arugula near strawberries, as they can attract slugs, which will happily munch on your arugula leaves.