Collard Greens in Zone 6A — Northeast

Collard greens are a fantastic addition to any Northeast garden, offering a unique, slightly bitter flavor that sweetens after a frost. Their versatility in the kitchen, from Southern-style braising to stir-fries, makes them a worthwhile crop to cultivate. Plus, the satisfaction of harvesting your own greens well into the fall, long after other crops have faded, is truly rewarding.

Our short growing season and the occasional late spring or early fall frost can be a challenge, but with careful timing, you can enjoy a bountiful harvest. With our roughly 178-day growing season, you have plenty of time to get your collards established and thriving.

Starting collard greens indoors is an option, particularly if you're eager to get a head start on the season. Begin your seeds indoors from mid-March through early April, about four weeks before you intend to transplant them outdoors. This can be especially helpful if we have a particularly late spring.

Use seed trays filled with a good seed-starting mix and provide consistent warmth and light. A heat mat can help speed up germination, and a grow light will prevent leggy seedlings. Bottom watering is key to avoid damping off – set your tray in a shallow dish of water and let the soil absorb the moisture from below.

Transplant your collard green seedlings outdoors from mid-April through mid-May, after the danger of a hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the cooler temperatures and stronger sunlight.

Space your collard greens 18-24 inches apart in well-drained soil. Keep an eye on the weather forecast, as we can still get surprise frosts in late April. If frost is predicted, cover your young plants with row covers or blankets.

Direct sowing collard greens is a perfectly viable option, especially if you want to skip the indoor seed-starting process. Sow your seeds directly into the garden from early April through mid-July. For a fall harvest, aim for the later end of that window.

Prepare the soil by loosening it and adding compost or well-rotted manure. Ensure the soil temperature is at least 60°F for optimal germination. Plant seeds about ½ inch deep and thin seedlings to 18-24 inches apart once they emerge. Direct sowing is easy, but you do run the risk of losing seedlings to pests or weather.

Collard greens need consistent moisture to thrive, especially in our Northeast climate. While we have fairly even rainfall, supplemental watering is often necessary, particularly during drier spells. Aim for about 1 inch of water per week, whether from rain or irrigation.

The "finger test" is a good way to gauge soil moisture. Stick your finger into the soil about 2 inches deep. If it feels dry, it's time to water. Water at the base of the plants rather than overhead to minimize the risk of fungal diseases, which can be a problem in our moderate-to-humid summers.

Overwatering can lead to root rot, so be mindful of drainage. Yellowing leaves can be a sign of overwatering, while wilting leaves indicate underwatering. Mulching around your collard greens with straw or wood chips helps retain moisture, suppress weeds, and regulate soil temperature.

You can expect your first harvest of collard greens from mid-June through late October, depending on when you planted them. Collard greens are ready to harvest when the lower leaves are 10-12 inches long. Harvest these outer leaves by cutting them off near the base of the plant.

Leave the top rosette of leaves intact to allow the plant to continue producing new leaves throughout the season. The flavor of collard greens actually sweetens after a frost, so don't be afraid to leave them in the garden as long as possible.

As the first frost approaches in mid- October, harvest any remaining large leaves. You can cover the plants with a row cover to extend the harvest a bit longer, but eventually, the cold will signal the end of the season.

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

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, dark green droppings, and white butterflies fluttering around.
• What causes it: Larvae of white cabbage butterflies. We often see multiple generations throughout our warm, humid summers.
• How to fix/prevent it: Bt spray is very effective and safe for consumption. Floating row covers are a good preventative measure. You can also handpick the caterpillars or 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. You might also notice sticky honeydew residue and curled or distorted new growth.
• What causes it: Rapidly reproducing sap-sucking insects. Populations explode in warm weather, and ants may farm them.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage ladybugs and lacewings, which are natural predators. Insecticidal soap can be used for heavy infestations, and neem oil works systemically. Avoid excess nitrogen fertilizer, which attracts them.

Cabbage Loopers

• What it looks like: Similar to cabbage worms, but these are pale green caterpillars that move in a looping motion. They also chew holes in leaves.
• What causes it: Larvae of moths. Like cabbage worms, they thrive in our moderate summers.
• How to fix/prevent it: Use Bt spray, handpick, or use row covers. Companion planting with dill can help deter them.

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: An oomycete pathogen that spreads in cool, humid conditions via wind-carried spores. This is more common during our cool, damp springs and falls.
• How to fix/prevent it: Remove affected leaves immediately. Improve air circulation by spacing plants appropriately. Water at the base, never overhead. Copper-based fungicides can be used preventatively.

Northeast Specific Challenges: Our moderate heat and moderate-to-humid humidity combined with even rainfall can create ideal conditions for both pests and fungal diseases. Consistent monitoring and proactive measures are key to keeping your collard greens healthy in our region. Also, deer pressure can be intense in the Northeast, so consider fencing or deer repellent.

Companion planting can be a helpful strategy for growing collard greens in the Northeast. Plant collards near onions and garlic, as their strong scent can deter pests like cabbage moths and aphids. Beets and potatoes also make good companions, as they don't compete for the same nutrients and can help improve soil structure. Dill is another excellent choice, attracting 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 and snails, which may also damage collard greens. Tomatoes are susceptible to similar fungal diseases, increasing the risk of spreading diseases to your collards in our moderately humid climate.