Collard Greens in Zone 8A — Pacific Northwest

Collard greens are a fantastic addition to any Pacific Northwest garden. Their slightly bitter, earthy flavor mellows with cooking, making them incredibly versatile in everything from soups and stews to stir-fries. Plus, with our cool nights and long, mild fall, the flavor actually sweetens after a light frost, giving you delicious greens well into the shoulder season.

While we might not have the intense heat some warm-season crops crave, collard greens thrive in our 203-day growing season. With a little attention to timing and a few regional-specific strategies, you can enjoy a bountiful harvest of these nutritious greens.

Starting collard greens indoors isn’t strictly necessary in our region, but it can give you a jump start, especially if you're eager for an early harvest. Sow seeds indoors from early to late March, about four weeks before you plan to transplant them outside. Use seed trays with a good seed-starting mix, and provide warmth and consistent moisture – bottom watering works great to prevent damping off.

Since spring can be slow to warm up here in the PNW, starting indoors gives the seedlings a head start against the cool soil. Just be sure to provide adequate light to prevent leggy growth.

Transplant your collard greens seedlings outdoors from early April through early May, once the soil has warmed up a bit. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space your plants 18-24 inches apart to allow for adequate growth. Keep an eye on the forecast – a late cold snap can still happen, so be ready to cover them if necessary.

Direct sowing collard greens is a simple and effective method for the PNW gardener. Sow seeds directly into the garden from late March through early August. This gives you a long window for succession planting and extended harvest.

Prepare the soil by loosening it and adding compost. Ensure the soil temperature is at least 50°F for good germination. Sow seeds ½ inch deep, and thin seedlings to 18-24 inches apart once they emerge. Direct sowing avoids transplant shock, but the plants may take slightly longer to mature compared to transplants.

Collard greens need consistent moisture to produce tender, flavorful leaves, but it's all about balance here in the PNW. While we have mild summers, the dry summer months mean you'll need to supplement rainfall.

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 two inches deep 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.

Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our sometimes overcast conditions. Underwatering leads to tough, bitter leaves, while overwatering can cause root rot. A layer of mulch, like straw or compost, helps retain moisture and regulate soil temperature, which is especially helpful during those mild summer days.

You can expect your first harvest of collard greens from early June through early November, about 75 days after planting. Harvest the lower leaves when they reach 10-12 inches long. This allows the top rosette to continue growing and producing more leaves.

To harvest, simply snap or cut the leaves off near the base of the plant. Avoid damaging the central stem. The flavor of collard greens actually improves after a light frost, so don't be afraid to leave them in the garden through late October.

As the first frost approaches, you can either harvest the entire plant or cover it to extend the harvest a bit longer. Even after a frost, the leaves are still edible, though they may become a bit softer.

Here are some common problems you might encounter with collard greens in the Pacific Northwest:

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, dark green droppings, and white butterflies fluttering nearby.
• What causes it: Larvae of white cabbage butterflies. They thrive in our mild summer conditions, leading to multiple generations.
• How to fix/prevent it: Use Bt spray, which is very effective. Floating row covers prevent butterflies from laying eggs. Handpick caterpillars when you see them. Interplant with aromatic herbs like thyme and sage to deter the butterflies.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides, sticky honeydew residue, and curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations can explode during our mild summers.
• How to fix/prevent it: Knock them off with a strong spray of water. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations, or neem oil for a systemic approach. Avoid excess nitrogen fertilizer, which attracts them.

Cabbage Loopers

• What it looks like: Pale green caterpillars that move in a looping motion. They chew large, irregular holes in leaves, often leaving the veins intact.
• What causes it: These caterpillars are the larvae of a nocturnal moth. They are most active during the warmer months.
• How to fix/prevent it: Handpick the caterpillars or use Bt (Bacillus thuringiensis) spray. Row covers can help prevent moths from laying eggs on your plants.

Downy Mildew

• What it looks like: Yellow patches on leaf tops with fuzzy gray-purple growth on undersides. Leaves brown and die from the bottom up.
• What causes it: Oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. It can be exacerbated by our overcast spring days.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation around plants. Water at the base, never overhead. Use copper-based fungicides for prevention. Plant resistant varieties if available.

Pacific Northwest Specific Challenges: While our mild summers are great for collard greens, the dry summer months can stress plants if not watered adequately. Slugs can also be a problem, especially for young seedlings. Use slug bait or traps to protect your plants. Late blight is less of a concern for collard greens than for tomatoes or potatoes, but it's still something to watch out for, especially during wet springs.

Collard greens benefit from companion planting. Onions and garlic help deter pests with their strong scent, protecting your collards from unwanted visitors. Beets and potatoes are good neighbors as they don't compete for the same nutrients and can help improve soil structure. Dill attracts beneficial insects like ladybugs and lacewings, which prey on aphids and other pests.

Avoid planting collard greens near strawberries or tomatoes. Strawberries can attract slugs, which will also munch on your collards. Tomatoes are susceptible to similar fungal diseases, potentially increasing the risk of problems for your collards, especially in our sometimes humid conditions.