Cabbage in Zone 7A — Mountain West

Cabbage might not be the first thing that comes to mind for high altitude gardening, but its crisp texture and slightly sweet flavor make it a worthwhile addition to your Mountain West garden. The cool nights we get even in summer really enhance its sweetness. From slaws to stir-fries, it's incredibly versatile in the kitchen. Plus, there’s real satisfaction in harvesting a beautiful, dense head of cabbage that you grew yourself.

Our short season and alkaline soil present some challenges, but careful timing and soil amendments can make growing cabbage in our Zone 7A gardens very manageable. With a growing season of around 173 days, starting indoors is the key to success.

Starting cabbage indoors is essential for a good spring harvest in the Mountain West. Begin in mid-February through early March, about six weeks before you plan to transplant. Use seed trays or small pots filled with a good quality seed-starting mix.

Keep the soil consistently moist, and consider bottom watering to avoid disturbing the delicate seedlings. Provide plenty of light – a grow light works wonders, especially with our late springs. Keeping the soil temperature around 70-75°F will help with germination.

Transplant your cabbage seedlings outdoors in early April through early May, 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 intense sun and cool nights of the Mountain West.

Space your plants 12-18 inches apart in rows. This gives them enough room to form nice, large heads. Be sure to protect young transplants from unexpected late-season snow or hail with row covers if needed.

Consistent moisture is key to growing healthy cabbage in our dry Mountain West climate. Water deeply and regularly, aiming for about 1-1.5 inches of water per week, especially during head formation. The "finger test" is a good way to gauge soil moisture – stick your finger about two inches into the soil; if it feels dry, it's time to water.

Water at the base of the plants rather than overhead to minimize water loss due to our low humidity and prevent sun scald on the leaves. During hotter periods, you may need to water more frequently.

Signs of underwatering include wilting or stunted growth. Overwatering, on the other hand, can lead to root rot, so make sure your soil drains well. A layer of mulch around your cabbage plants helps retain moisture and regulate soil temperature, which is especially helpful with our intense sun and fluctuating temperatures.

You can expect your first cabbage harvest from mid-June through early August, about 70 days after transplanting. The best indicator of ripeness is a firm, solid head when squeezed. It should also be the full size expected for the variety you're growing.

To harvest, use a sharp knife to cut the head at its base. Leave the outer leaves intact, as they can sometimes produce smaller side heads.

As the first frost approaches in early October, harvest any remaining mature heads. Smaller, immature heads likely won’t have time to fully develop before the cold sets in. You can also try covering plants with a frost blanket to extend the season a bit longer.

Here are some common cabbage problems you might encounter in the Mountain West:

• 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: Pale green caterpillars that move in a looping fashion. They chew large, ragged holes in the leaves, often leaving behind dark green or black droppings.
• What causes it: Similar to cabbage worms, these are the larvae of moths. They thrive in warm weather.
• How to fix/prevent it: Handpicking is effective for small infestations. Bt spray works well. Encourage beneficial insects like parasitic wasps and 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 fluctuating temperatures can also contribute.
• How to fix/prevent it: Maintain consistent soil moisture. Water deeply but less frequently. Harvest heads as soon as they are mature to prevent over-ripening and splitting.
• 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.

Mountain West Specific Challenges: Our intense sun can sometimes cause sunscald on cabbage heads, so ensure adequate watering and consider providing some afternoon shade during the hottest part of the summer. The dry air can also stress plants, so consistent watering and mulching are essential. Hail can also damage leaves, so be prepared to cover plants during severe weather.

Good companion plants for cabbage in the Mountain West include green beans, celery, onions, potatoes, and dill. Green beans fix nitrogen in the soil, benefiting cabbage growth. Celery repels cabbage white butterflies. Onions deter many pests, while potatoes don't compete for the same nutrients. Dill attracts beneficial insects that prey on cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and peppers can stunt cabbage growth, while strawberries are susceptible to similar fungal diseases, increasing the risk of spreading problems.