Collard Greens in Zone 7B — Pacific Northwest

Collard greens thrive in our mild summers and even taste sweeter after a light frost, making them a perfect fit for the Pacific Northwest garden. Their sturdy leaves hold up well in stir-fries, soups, or even fermented, and they’re satisfying to grow, offering a generous harvest over many months. You'll appreciate them even more because cool nights improve the flavor of many of your garden crops.

While we might not have the long, hot summers of other regions, our 193-day growing season provides ample time to enjoy collards. We might need to be mindful of slugs and the occasional bout of downy mildew, but with a bit of planning, you'll be enjoying homegrown collards from summer well into fall.

Starting collards indoors gives you a head start, especially with our slow springs. If you want to get a jump on the season, aim to sow seeds indoors from mid-March through early April, about four weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light; a simple shop light works wonders.

Consistent moisture is key, and bottom watering is a great way to avoid damping-off; just set the tray in a shallow dish of water for a few minutes until the soil surface is moist. Starting indoors isn't essential, but it can be helpful if you want earlier harvests, especially since our overcast spring days can slow down growth.

Transplant your collard green seedlings outdoors from mid-April through mid-May, once they have a few sets of true leaves. 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 the plants 18-24 inches apart to give them room to grow. Keep an eye on the weather forecast; a late cold snap can set them back, so be ready to cover them if needed.

Direct sowing collard greens is an easy option, especially if you're not in a rush. Sow seeds directly into the garden from early April through late July. The soil needs to be at least 50°F for good germination, so wait until the soil has warmed up a bit.

Prepare the soil well, and sow seeds about ½ inch deep, spacing them a few inches apart. Thin seedlings to 18-24 inches once they're a few inches tall. Direct sowing can be a bit slower than transplanting, but it avoids transplant shock and works well if you have the space.

Collard greens need consistent moisture to produce tender, flavorful leaves, but we don't need to overdo it here in the PNW. During our wet springs, you likely won't need to water much at all, if ever. Once our dry summer months arrive, though, regular watering becomes important.

Check the soil moisture by sticking your finger about 2 inches deep; if it feels dry, it's time to water. Aim for about 1 inch of water per week, especially during hotter periods. Watering at the base of the plants is best to avoid wetting the leaves, which can encourage downy mildew.

If the leaves are wilting or turning yellow, you might be underwatering. Conversely, if the leaves are yellowing and the soil feels soggy, you're likely overwatering. A layer of mulch, like straw or compost, can help retain moisture and keep the soil cool during our mild summer heat.

You can start harvesting collard greens from mid-June through early November, about 75 days after planting. Look for the lower leaves to be about 10-12 inches long. Harvest by cutting the outer leaves, leaving the top rosette intact; this allows the plant to continue producing throughout the season.

The flavor of collard greens actually sweetens after a light frost, so don't be afraid to leave them in the garden as long as possible. As our first frost approaches in late October, you can harvest the entire plant or cover it with a blanket to extend the harvest a bit longer.

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

Cabbage Worms

• What it looks like: Smooth green caterpillars on leaves, irregular holes, dark green droppings, white butterflies.
• What causes it: Larvae of white cabbage butterflies, multiple generations in warm weather.
• How to fix/prevent it: Bt spray is effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs.

Aphids

• What it looks like: Clusters of tiny insects on stems and leaf undersides, sticky honeydew, curled growth.
• What causes it: Rapid-reproducing sap-sucking insects, populations explode in warm weather.
• How to fix/prevent it: Strong water spray. Encourage ladybugs and lacewings. Insecticidal soap. Neem oil. Avoid excess nitrogen.

Cabbage Loopers

• What it looks like: Similar to cabbage worms but move in a looping motion. Eat large holes in leaves.
• What causes it: Larvae of cabbage looper moths.
• How to fix/prevent it: Handpick. Bt spray. Encourage natural predators like birds and parasitic wasps.

Downy Mildew

• What it looks like: Yellow patches on leaf tops, fuzzy gray-purple growth on undersides, leaves die from the bottom up.
• What causes it: Oomycete pathogen, spreads in cool, humid conditions.
• How to fix/prevent it: Remove affected leaves. Improve air circulation. Water at the base. Copper-based fungicides for prevention.

Pacific Northwest Specific Challenges: Our mild summer heat and dry-summer rainfall often mean fewer pest pressures than other regions. Slugs can be a problem, especially in spring, so use slug bait or traps. Late blight, while more common on tomatoes and potatoes, can occasionally affect collards, so good air circulation and avoiding overhead watering are key.

Companion planting can help your collard greens thrive. Onions and garlic are great companions because their strong scent deters pests. Beets and potatoes are also good choices, as they don't compete for the same nutrients. Dill attracts beneficial insects that prey on pests like aphids.

Avoid planting collard greens near strawberries or tomatoes. Strawberries can attract slugs, which will happily munch on your collards, and tomatoes can harbor diseases that might spread to your collards.