Swiss Chard in Zone 7A — Pacific Northwest

Swiss chard is a fantastic addition to any Pacific Northwest garden. Its mild, earthy flavor shines in everything from stir-fries to soups, and its vibrant colors add a visual punch to your plate. Plus, those cool nights we get here really bring out the sweetness in leafy greens.

Our wet springs and mild summers can present some challenges, but with a little planning, you can enjoy a bountiful chard harvest. Our 183-day growing season offers plenty of time to get this semi-hardy crop established and producing.

While you can direct sow Swiss chard, starting indoors gives you a head start, especially with our sometimes slow-to-warm spring soil. If you want to get a jump on the season, sow seeds indoors from mid-March through early April, about four weeks before you plan to transplant.

Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist by bottom watering – set the tray in a shallow dish of water and let the soil soak it up from the bottom. Provide warmth and plenty of light; a sunny windowsill or grow lights work well.

Transplant your Swiss chard seedlings outdoors from mid-April through mid-May, after the danger of hard frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week.

Choose a spot with full sun to partial shade and space the seedlings 8-12 inches apart. Our overcast spring days mean even "full sun" spots are gentler than in other climates, which chard appreciates. Keep an eye on the weather forecast; a late cold snap can still happen, so be ready to cover your young plants if needed.

Direct sowing Swiss chard is a simple and reliable method, especially since our mild summers give you a long window for succession planting. Sow seeds directly into the garden from early April through mid-August.

Prepare the soil by loosening it and amending with compost. Plant seeds about ½ inch deep and 8-12 inches apart. Keep the soil consistently moist until germination, which usually takes about a week or two depending on soil temperature. A soil thermometer can be helpful to know when the soil is consistently above 50°F.

Swiss chard needs consistent moisture, but it's more tolerant of drier conditions than spinach, making it a good choice for our dry summer months. Aim for about 1 inch of water per week, but adjust based on rainfall and soil conditions.

During our wet springs, you may not need to water at all, but once the dry summer hits, check the soil moisture regularly. Stick your finger about 2 inches deep into the soil; if it feels dry, it's time to water. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our sometimes-humid springs.

Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to yellowing leaves and root rot. A layer of mulch around your chard plants will help retain moisture and suppress weeds, which is especially helpful during those dry summer months.

You can expect your first Swiss chard harvest from late May through late October, about 55 days after planting. Harvest the outer stalks when they reach 8-12 inches in length. The colorful stems (red, yellow, or white) are perfectly edible and add a nice touch to any dish.

Cut the stalks at the base of the plant, leaving the inner leaves to continue growing. This cut-and-come-again method allows for continuous harvests throughout the season. As our first frost approaches in mid-October, harvest any remaining large leaves to use in soups or stir-fries, or consider covering your plants with a frost blanket to extend the harvest a bit longer.

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

Leaf Miners

• What it looks like: Tan, winding tunnels inside the leaves.
• What causes it: Small flies lay eggs on the leaves, and the larvae burrow inside to feed. Our mild summers and relatively few hard freezes allow these pests to thrive.
• How to fix/prevent it: Cover young plants with row covers to prevent the flies from laying eggs. Remove and destroy any infested leaves as soon as you see them.

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: A strong water spray can knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap can be used for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer (it attracts them).

Cercospora Leaf Spot

• What it looks like: Small, circular spots with tan or gray centers and reddish-brown borders on the leaves.
• What causes it: A fungal disease that thrives in warm, humid conditions. While our summers are dry, our springs can be quite humid, which can contribute to this problem.
• How to fix/prevent it: Provide good air circulation by spacing plants properly. Avoid overhead watering. Remove and destroy infected leaves. Use 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. Our wet springs and mild climate provide ideal conditions for slugs.
• 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: Late blight isn't usually a major issue for Swiss chard itself, but it can affect nearby tomatoes and potatoes, so be mindful of crop rotation. Our cool soil in spring can slow down growth, so consider warming the soil with plastic mulch before planting. While our summers are mild, providing some afternoon shade during the hottest part of the day can prevent bolting. And always be vigilant about slugs, especially during our wet springs!

Swiss chard plays well with several other vegetables in the Pacific Northwest garden. Lettuce thrives in similar conditions and provides ground cover to help retain moisture. Onions and garlic deter pests with their strong scent. Green beans fix nitrogen in the soil, benefiting chard's growth. Cabbage family members like broccoli and kale also make good companions, as they share similar growing requirements.

Avoid planting Swiss chard near corn or potatoes. Corn competes for nutrients and can shade the chard too much. Potatoes are susceptible to late blight, which, while not a direct threat to chard, can spread in the garden.