Swiss Chard in Zone 7B — Pacific Northwest

Swiss chard is a workhorse in the Pacific Northwest garden, offering beautiful color and a mild, earthy flavor that thrives in our cool nights. It’s incredibly versatile – use it like spinach in salads, sautés, or soups. The satisfaction of harvesting those vibrant leaves, knowing they’re packed with nutrients and grown right in your backyard, is hard to beat.

While our mild summers are ideal for chard, we do have our challenges. Cool soil in spring and the potential for late blight can be concerns. But with a little planning and attention, you can enjoy a bountiful harvest throughout our long, 193-day growing season.

Starting Swiss chard indoors isn't essential in our region, but it can give you a head start, especially if you're eager to get a jump on the season. If you're going this route, aim to start seeds indoors from mid-March through early April, about four weeks before you plan to transplant. This helps get ahead of our slow-starting springs.

Use seed trays filled with a good seed-starting mix. Keep them consistently moist by bottom watering – set the tray in a shallow dish of water and let the soil soak it up from the bottom. Place the trays in a warm spot with plenty of light, either a sunny windowsill or under grow lights.

Transplant your Swiss chard seedlings outdoors from mid-April through mid-May, once the soil has warmed up a bit. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of direct sunlight and increase the time each day.

When transplanting, space the seedlings 8-12 inches apart in well-drained soil. Keep an eye on the weather, as we can still get some cool, overcast spring days. If a late frost is predicted, cover your young plants with row covers or blankets.

Direct sowing is a perfectly viable option for Swiss chard in the Pacific Northwest, and often the easiest! You can direct sow from early April through mid-August, giving you a long window for multiple plantings. Direct sowing avoids transplant shock and allows the plants to establish strong root systems.

Prepare the soil by loosening it and adding compost. Sow seeds about ½ inch deep and 8-12 inches apart. Keep the soil consistently moist until the seeds germinate. One potential downside is that slugs may find your young seedlings tasty, so be prepared to take action against them.

Swiss chard appreciates consistent moisture, but it's also fairly resilient, making it a great choice for our dry summer months. Aim for moderate watering, keeping the soil consistently moist but not waterlogged. The "finger test" is your friend – stick your finger about two inches into the soil; if it feels dry, it's time to water.

During our wet springs, you may not need to water at all, relying instead on natural rainfall. Once our dry summer months arrive, you'll likely need to water one to two times per week, providing about 1 inch of water each time. Water at the base of the plants to avoid wetting the leaves, which can help prevent fungal diseases in our dry-summer climate.

Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot. A layer of mulch around your Swiss chard plants can help retain moisture and suppress weeds – straw or wood chips work well in our region.

You can expect your first harvest of Swiss chard from late May through early November, depending on when you planted. The leaves are ready to harvest when they are 8-12 inches long. The colorful stems (red, yellow, white) are also edible and delicious!

To harvest, simply cut the outer stalks at the base of the plant, leaving the inner leaves to continue growing. This allows for continuous harvesting throughout the season. Regularly harvesting encourages new growth and keeps your plants producing.

As our first frost approaches in late October, you can extend your harvest by covering the plants with row covers or a cold frame. Swiss chard can tolerate a light frost, and the leaves often taste even sweeter after a touch of cold.

Here are some common problems you might encounter with Swiss chard in the Pacific Northwest:

Leaf Miners

• What it looks like: Tan, winding tunnels or blotches inside the leaves.
• What causes it: Small flies lay eggs on the leaves, and the larvae tunnel through the leaf tissue.
• How to fix/prevent it: Cover plants with row covers to prevent the flies from laying eggs. Remove and destroy infested leaves. Encourage beneficial insects like parasitic wasps.

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: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer (it attracts them).

Cercospora Leaf Spot

• What it looks like: Small, circular spots on leaves that start as yellow and turn brown with gray centers. Spots may merge, causing leaves to yellow and die.
• What causes it: A fungal disease that thrives in warm, humid conditions.
• How to fix/prevent it: Provide good air circulation by spacing plants properly. Remove and destroy infected leaves. Avoid overhead watering. Apply a copper-based fungicide if necessary.

Slugs

• What it looks like: Irregular holes in leaves, especially low-growing plants. Silvery slime trails on leaves and soil. Damage worse at night and in wet weather.
• What causes it: Gastropods that feed at night in moist conditions. Hide under mulch, boards, and debris during the day.
• How to fix/prevent it: Beer traps (shallow dish of beer sunk into soil). Iron phosphate bait (pet-safe). Remove hiding spots. Water in morning so soil surface dries by evening. Copper tape around beds. Diatomaceous earth around plants.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall can actually be beneficial for Swiss chard, as it’s more heat-tolerant than spinach. However, slugs are a constant battle, especially during our wet springs. Keep an eye out for them and take action early to prevent significant damage. Late blight is less of a concern for chard than for tomatoes or potatoes, but it's still good to practice crop rotation and avoid overhead watering to minimize the risk.

Swiss chard benefits from companion planting. Lettuce makes a great companion because it provides ground cover, helping to retain moisture and suppress weeds. Onions and garlic deter pests like aphids with their strong scent. Green beans fix nitrogen in the soil, which benefits chard's growth. Cabbage family members like broccoli and kale also do well planted near Swiss chard.

Avoid planting Swiss chard near corn or potatoes. Corn can compete for nutrients, and potatoes are susceptible to similar diseases, potentially increasing the risk of problems in your garden.