Cabbage in Zone 6B — Mountain West

Cabbage is a fantastic addition to any Mountain West garden. Its crisp, slightly sweet flavor shines in slaws, stir-fries, and even hearty soups, perfect for those cool evenings we get even in the middle of summer. Plus, there's a real satisfaction in harvesting a dense, tightly packed head of cabbage that you nurtured from a tiny seed.

Our high altitude, intense sun, and alkaline soil present unique challenges, but with careful timing, you can absolutely grow beautiful cabbages. Our 163-day growing season might seem short, but it's plenty of time to get a spring crop in, and even a fall crop if you plan accordingly.

To get a head start on the season, start your cabbage seeds indoors from late February through mid March. This gives them about 6 weeks to develop before transplanting. Use seed trays filled with a good seed-starting mix.

Keep the trays warm – around 70°F is ideal – and provide plenty of light. A simple shop light works great, but make sure it's close to the seedlings. Water from the bottom to avoid damping off. This is especially important since our springs often have lingering cold snaps.

Remember, our spring here in the Mountain West can be slow to arrive, so starting indoors is crucial for spring harvests.

Transplant your cabbage seedlings outdoors from mid April through early May, after the worst of the spring frosts have passed. Before you plant them in the ground, harden them off by gradually exposing them to outdoor conditions for about a week.

Space the seedlings 12-18 inches apart to give them plenty of room to grow. Even though we get a lot of intense sun, keep an eye out for late frosts or even hail, which can be tough on young plants. Be ready to cover them if necessary.

Cabbage needs consistent moisture to thrive, but overwatering can be just as bad as underwatering, especially in our alkaline soil. Aim to keep the soil consistently moist, but not soggy.

During the cooler spring months, you might only need to water once or twice a week. As the weather warms up in summer, increase watering to 1-2 inches per week, depending on rainfall. Stick your finger about 2 inches deep into the soil – if it feels dry, it's time to water. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in other regions but isn't much of a concern in our dry Mountain air.

Wilting leaves are a sign of underwatering, while yellowing leaves can indicate overwatering. Mulching around your cabbage plants with straw or wood chips helps to retain moisture and suppress weeds, which is always a plus.

You can expect your first cabbage harvest from mid June through early August, about 70 days after transplanting. The key is to check the firmness of the head. When you squeeze it gently, it should feel solid and dense.

Harvest when the head reaches full size for its variety. Use a sharp knife to cut the cabbage head at the base of the plant. Leave the outer leaves intact, and you might get some smaller side shoots that you can harvest later.

As our first frost approaches in early October, harvest any remaining mature heads. Smaller, immature heads can be used in slaws and stir-fries too.

Here are some common problems you might encounter with cabbage 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 motion. Similar damage to cabbage worms, but often with more extensive leaf damage.
• What causes it: Larvae of cabbage looper moths. Often more prevalent in warmer weather.
• How to fix/prevent it: Similar to cabbage worms, Bt spray is effective. Handpicking can also work. Row covers can help prevent moths from laying eggs.
• Splitting
• What it looks like: The cabbage head cracks open, usually after a period of heavy rain or inconsistent watering.
• What causes it: Rapid growth due to fluctuating moisture levels. The inside of the cabbage grows faster than the outer leaves can expand.
• How to fix/prevent it: Consistent watering is key. Try to maintain even soil moisture. If heavy rain is expected, you can try twisting the cabbage head slightly to break some of the roots and slow down growth.
• 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 moderate-at-altitude heat and low humidity generally mean fewer disease problems than other regions, but intense sunlight can still stress plants. Consistent watering and some afternoon shade during the hottest part of the summer can help. Also, our alkaline soil can exacerbate nutrient deficiencies, so amend your soil with compost regularly.

Companion planting can be a great way to improve your cabbage crop. Green beans fix nitrogen in the soil, benefiting cabbage growth. Celery repels cabbage white butterflies, while onions deter cabbage root flies. Potatoes can help break up the soil, improving drainage. 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 can compete for nutrients.