Cabbage in Zone 6A — Mountain West

Cabbage is a surprisingly rewarding crop for us Mountain gardeners. The cool nights we get, even in summer, actually *improve* the flavor, making for some incredibly sweet and crisp heads. Plus, it's so versatile – from slaws and ferments to soups and stir-fries, you'll find yourself using it constantly.

Our short growing season (around 153 days) and alkaline soil definitely present challenges. But, by starting seeds indoors and choosing the right varieties, you can absolutely enjoy a bountiful cabbage harvest. Timing is key, and with a little planning, you'll be enjoying fresh cabbage from your garden.

To get a jump start on our short growing season, you'll want to start your cabbage seeds indoors from late February through mid March. This gives you about 6 weeks to get them strong before transplanting. Use seed trays or small pots filled with a good seed-starting mix.

Keep the soil consistently moist by bottom watering to prevent damping off, and provide plenty of light. A simple shop light will do. Given our late springs here in the mountains, don't be tempted to rush things outdoors too early.

Transplant your cabbage seedlings outdoors from mid April through mid May, after 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 fluctuating temperatures we often see.

Space your cabbage plants 12-18 inches apart in rows. This allows for good air circulation, which is especially important in our dry climate. Make sure to amend your soil with compost before planting, as our alkaline soil can be tough on young seedlings.

Cabbage needs consistent moisture to thrive, especially with our dry Mountain air and low rainfall. Aim to water deeply about once or twice a week, depending on the weather. The "finger test" is your best friend: stick your finger about 2 inches into the soil. If it feels dry, it's time to water.

Give them about 1-1.5 inches of water per week. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases, even in our low humidity. Signs of underwatering include wilting leaves and stunted growth. Overwatering can lead to root rot, indicated by yellowing leaves and a generally unhappy plant.

A good layer of mulch, like straw or wood chips, will help retain moisture in the soil and keep the roots cool during our warm summer days. This is especially important because we don't get much rain here.

You can expect your first cabbage harvest from late June through mid August, about 70 days after transplanting. The key is to check for firmness. The head should feel solid and dense when you gently squeeze it. It should also be a good size for the variety you're growing.

To harvest, use a sharp knife to cut the head at the base of the plant. Leave the outer leaves intact, as they can sometimes produce smaller secondary heads. As our first frost approaches around early October, harvest any remaining heads, even if they aren't quite fully mature. They'll still be delicious!

Here are some common problems you might encounter growing 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. They chew large, irregular holes in leaves.
• What causes it: Similar to cabbage worms, these are the larvae of a moth. They thrive in warm weather.
• How to fix/prevent it: Bt spray works well on loopers too. Handpicking is also effective, especially for smaller infestations. Encourage beneficial insects.

Splitting

• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering. A sudden heavy watering after a period of drought causes the head to swell too quickly.
• How to fix/prevent it: Consistent watering is key. Mulch to retain moisture. Harvest heads as soon as they are mature to prevent 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 scorch cabbage leaves, so providing some afternoon shade during the hottest part of the summer can be helpful. Also, our alkaline soil can make it difficult for cabbage to absorb nutrients, so amending the soil with compost is essential. Hail can also damage the leaves, so consider using row covers if hail is predicted.

Good companions for cabbage include green beans, celery, onions, potatoes, and dill. Green beans fix nitrogen in the soil, which benefits cabbage. Celery repels cabbage white butterflies. Onions deter many pests. Potatoes don't compete for the same nutrients. Dill attracts beneficial insects that prey on cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, and peppers. Tomatoes and peppers can stunt the growth of cabbage. Strawberries compete for the same nutrients and can attract pests that also affect cabbage. These plants do better in separate areas of your garden, especially given our limited space at altitude.