Cabbage in Zone 6A — Great Plains

Cabbage is a worthwhile addition to any Great Plains garden. Its crisp texture and mild flavor are delicious raw in slaws or cooked in hearty dishes, perfect for both summer and fall meals. Plus, there’s something deeply satisfying about harvesting a tightly packed head of cabbage that you grew yourself in spite of our sometimes challenging climate.

Sure, we face extreme weather on the Plains, but with careful timing, you can definitely grow a successful cabbage crop. Starting seeds indoors gives you a head start, maximizing our roughly 188-day growing season and ensuring you get a good harvest before the first frost hits.

For a spring cabbage harvest, start your seeds indoors from mid-February through early March, about six weeks before you plan to transplant them outside. Use seed trays or small pots filled with a good seed-starting mix. Keep the soil consistently moist, and provide warmth with a heat mat if needed.

Bottom watering is especially helpful at this stage, as it prevents damping off and encourages strong root growth. Place your seed trays in a shallow tray of water and let the soil soak it up from the bottom. Once seedlings emerge, provide plenty of light with a grow light or a sunny windowsill. Keep in mind that our springs here on the Plains can be variable, so be prepared to adjust your setup as needed.

Transplant your cabbage seedlings outdoors in early to late April, once the danger of 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 wind and temperature swings common in the Plains.

Space your cabbage plants 12-18 inches apart in rows. Ensure the soil is well-drained and enriched with compost. Be mindful of potential late frosts and have row covers ready to protect your young plants if needed.

Cabbage needs consistent moisture to form tight, healthy heads, but our variable rainfall on the Plains can make this tricky. During the hot summer months, especially if rainfall is scarce, aim to give your cabbage plants about 1-1.5 inches of water per week. Use the "finger test" to check soil moisture – 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 to avoid wetting the leaves, which can encourage fungal diseases in our low-to-moderate humidity. Overhead watering is fine if done early in the day, giving the leaves time to dry before nightfall. Signs of underwatering include wilting leaves and slow growth. Overwatering, on the other hand, can lead to root rot.

Mulching around your cabbage plants with straw or wood chips helps retain soil moisture and regulate soil temperature, which is especially beneficial during our extreme temperature swings. Just be sure to leave some space around the stem to prevent rot.

You can expect to harvest your cabbage from early June through late July, about 70 days after transplanting. The best way to tell if a cabbage head is ready is to give it a gentle squeeze. If it feels firm and solid, it's ready to harvest.

Also, make sure the head has reached the full size expected for the variety you planted. To harvest, use a sharp knife to cut the cabbage head at its base, leaving a few outer leaves intact.

As our first frost approaches in mid- October, harvest any remaining cabbage heads, even if they're not quite fully mature. Smaller heads can still be used in cooking or pickling.

Here are a few common problems you might encounter growing cabbage in the Great Plains:

Cabbage Worms

• What it looks like: Smooth green caterpillars on brassica leaves. Irregular holes chewed in leaves. Dark green droppings. White butterflies hovering around plants.
• What causes it: Larvae of white cabbage butterflies. Multiple generations per season in warm climates.
• How to fix/prevent it: Bt spray is very effective. Floating row covers prevent egg laying. Handpick caterpillars. Interplant with aromatic herbs (thyme, sage). Encourage parasitic wasps.

Cabbage Loopers

• What it looks like: Similar to cabbage worms, but these caterpillars move in a looping motion. They also chew holes in leaves.
• What causes it: Cabbage looper moths lay eggs on brassicas.
• How to fix/prevent it: Use Bt spray, handpick caterpillars, and use floating row covers. Encourage beneficial insects like lacewings.

Splitting

• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering, especially heavy watering after a dry spell. Rapid growth due to plentiful moisture and fertility.
• How to fix/prevent it: Provide consistent moisture throughout the growing season. Avoid over-fertilizing. Choose split-resistant varieties.

Clubroot

• What it looks like: Stunted growth, wilting in afternoon heat, yellowing leaves. Roots are swollen, distorted, and club-shaped when dug up.
• What causes it: Soil-borne pathogen (Plasmodiophora brassicae) that persists in soil for 10+ years. Favors acidic, wet soil.
• How to fix/prevent it: Raise soil pH to 7.0-7.2 with lime. Improve drainage. Rotate brassicas on a 7-year cycle. Remove and destroy infected plants (don't compost). Start transplants in sterile mix.

Great Plains Specific Challenges: The hot summers can stress cabbage plants, making them more susceptible to pests and diseases. Our variable rainfall means you need to be vigilant about watering. Wind protection is also essential to prevent damage to the leaves.

Companion planting can help your cabbage thrive in the Great Plains. Green beans are good companions because they fix nitrogen in the soil, benefiting cabbage. Celery is thought to deter cabbage white butterflies. Onions repel many pests that bother cabbage. Potatoes don't directly benefit cabbage, but they don't compete for resources and can help break up the soil. Dill attracts beneficial insects that prey on cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and peppers can inhibit cabbage growth. Strawberries compete for nutrients and can attract pests that also affect cabbage.