Collard Greens in Zone 3A — Great Plains

Collard greens offer a unique, slightly bitter flavor that’s fantastic in soups, stews, or simply sautéed. They're surprisingly cold-hardy, which makes them a great choice for extending your harvest in our short Plains season. Plus, there's nothing quite like the satisfaction of harvesting your own greens after a long winter.

Our Great Plains climate definitely throws some curveballs with its extreme temperature swings, hail risk, and variable rainfall. However, collards can be successfully grown here with careful timing and attention to their needs. With our 108-day growing season, you'll want to be strategic.

Starting collard greens indoors isn't essential, but it can give you a head start, especially in the northern Plains. If you choose to start indoors, aim to sow your seeds from mid-April through mid-May, about four weeks before you plan to transplant them outside. Use seed trays or small pots filled with a good seed-starting mix, and keep them warm and consistently moist by bottom watering.

A sunny windowsill might work, but supplemental light from a grow light will give you stronger, stockier seedlings. Remember that spring in the Plains can be unpredictable, so having seedlings ready gives you flexibility if the weather delays outdoor planting.

Transplanting collard greens outdoors should happen from late May through mid-June, once the danger of a hard frost has passed. Before you move them outside permanently, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings common in our region.

Space your collard plants 18-24 inches apart in rows. This gives them plenty of room to grow. At transplant time, keep an eye on the forecast for late frosts or hail, and be ready to cover your young plants if necessary.

Direct sowing collard greens is a viable option, particularly if you're looking for a low-maintenance approach. Sow seeds from mid-May through mid-June, when the soil has warmed up to at least 60°F. Prepare your garden bed by loosening the soil and adding compost or well-rotted manure.

Plant seeds about ½ inch deep and keep the soil consistently moist until they germinate. Thin seedlings to 18-24 inches apart once they have a few true leaves. Direct sowing avoids transplant shock, but you'll need to stay on top of weeding to give your collards a good start.

Collard greens need consistent moisture to produce tender, flavorful leaves. While they are more heat-tolerant than some other brassicas, they still suffer in our hot Plains summers if they don't get enough water. Aim for about 1-1.5 inches of water per week, especially during dry spells.

Check the soil moisture regularly using the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Water deeply at the base of the plants, rather than overhead, to minimize fungal diseases in our low-to-moderate humidity.

During the hottest part of the summer, you may need to water more frequently, especially if rainfall is scarce. Signs of underwatering include wilting leaves and slow growth, while yellowing leaves can indicate overwatering. A good layer of mulch, such as straw or wood chips, will help retain soil moisture and suppress weeds.

You can expect your first collard greens harvest from late July through mid-September, about 75 days after planting. The best time to harvest is when the lower leaves are 10-12 inches long and a healthy green color. Don't wait too long, or they can become tough.

To harvest, simply snap off the outer leaves, leaving the central rosette to continue growing. This allows for continuous harvesting 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 the first frost approaches in early September, harvest any remaining large leaves. You can blanch and freeze them for later use, or enjoy them in a hearty fall stew. Even after a light frost, the core plant may survive and provide you with a few more leaves.

Here are the most common problems you might encounter with collard greens in the Great Plains:

Cabbage Worms

• What it looks like: Smooth, green caterpillars chewing irregular holes in leaves, leaving dark green droppings behind. You might also see white cabbage butterflies fluttering around.
• What causes it: These are the larvae of white cabbage butterflies. They can have multiple generations in a season, especially if we have a warmer-than-usual summer.
• How to fix/prevent it: Bt spray is very effective and safe. Floating row covers will prevent the butterflies from laying eggs in the first place. Handpicking caterpillars is also an option. Consider interplanting with aromatic herbs like thyme and sage to deter the butterflies, and encourage parasitic wasps, which prey on cabbage worms.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and undersides of leaves. You might also notice sticky honeydew and curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that reproduce rapidly, especially in warm weather. Ant colonies sometimes "farm" them for the honeydew they produce.
• How to fix/prevent it: A strong spray of water can knock aphids off plants. Encourage ladybugs and lacewings, which are natural predators. Insecticidal soap is effective for heavy infestations, and neem oil works systemically. Avoid excess nitrogen fertilizer, as it attracts aphids.

Cabbage Loopers

• What it looks like: Pale green caterpillars that move in a looping motion. They chew large holes in leaves, often leaving only the veins.
• What causes it: Similar to cabbage worms, these are the larvae of a moth. They thrive in warm weather.
• How to fix/prevent it: Handpicking is effective for small infestations. Bt spray also works well. Encourage natural predators like birds and parasitic wasps. Floating row covers can prevent moths from laying eggs.

Downy Mildew

• What it looks like: Yellow patches on the tops of leaves, with fuzzy, gray-purple growth on the undersides. Leaves will eventually brown and die from the bottom up.
• What causes it: This is a disease caused by a pathogen that spreads in cool, humid conditions via wind-carried spores.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation by spacing plants properly. Water at the base of the plants, never overhead. Copper-based fungicides can be used for prevention. Plant resistant varieties if available.

Great Plains Specific Challenges: Our region's extreme temperature swings and variable rainfall can stress collard greens, making them more susceptible to pests and diseases. Hot, dry spells can encourage aphids and cabbage loopers, while periods of humidity can create conditions favorable for downy mildew. Consistent monitoring and prompt action are key to keeping your collard greens healthy.

Companion planting can really help your collard greens thrive in the Great Plains. Onions and garlic are excellent companions because their strong scent deters many common pests, like cabbage moths and aphids. Beets and potatoes are also good choices, 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 are susceptible to some of the same fungal diseases as collards, increasing the risk of spread. Tomatoes can stunt the growth of collards, possibly due to allelopathic effects (the release of chemicals that inhibit growth).