Cabbage in Zone 3B — Mountain West

Cabbage might just become your new favorite staple in your Mountain West garden. Its crisp, slightly sweet flavor is fantastic fresh, fermented into sauerkraut, or added to slaws and stir-fries. Plus, the satisfaction of harvesting a perfectly formed head of cabbage after nursing it through our challenging growing season is hard to beat.

Our short growing season and intense sun at altitude demand careful planning, but don't let that scare you. By starting your cabbage indoors and choosing the right varieties, you can absolutely enjoy a delicious harvest within our 108-day window. Timing is everything, and we'll walk you through it.

Starting your cabbage indoors is the key to getting a head start on our short growing season. Aim to sow your seeds from late March through mid April, roughly six weeks before you plan to transplant them outside. This gives them a fighting chance to mature before our early September frosts arrive.

Use seed trays or small pots filled with a good quality seed starting mix. Ensure the trays are kept consistently moist – bottom watering is ideal to prevent damping off. Place them in a warm location, around 70°F, and provide plenty of light. A grow light is highly recommended, especially given our late spring characterized by cloudy days.

Transplant your cabbage seedlings outdoors from mid May through early June, 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. Start with a few hours of shade and increase the time and sun exposure each day.

When transplanting, space your cabbage plants 12-18 inches apart in rows. Our intense sun can be tough on young transplants, so consider using shade cloth for the first few days, especially if you're experiencing a particularly warm spell. Remember, even in late May and early June, a surprise frost is possible, so be ready to cover your plants if needed.

Cabbage needs consistent moisture to form those tight, beautiful heads we're after. In our dry Mountain West climate, this means paying close attention to watering. Aim for about 1-1.5 inches of water per week, especially during head formation.

Use the "finger test" to check the soil moisture: stick your finger about 2 inches deep near the base of the plant. If the soil feels dry, it's time to water. Water deeply at the base of the plant rather than overhead to minimize water loss through evaporation in our low humidity.

Signs of underwatering include wilting or stunted growth. Overwatering, on the other hand, can lead to root rot, especially in our alkaline soils. Yellowing leaves can be a sign of either problem, so check the soil moisture carefully. A layer of organic mulch, like straw or wood chips, can help retain moisture and regulate soil temperature, which is a huge benefit with our temperature swings.

You can usually expect your first cabbage harvest from mid July through early September, about 70 days after transplanting. The best way to tell if a cabbage head is ready is to give it a gentle squeeze. It should feel firm and solid all the way through. Also, make sure it's reached the full size expected for its variety.

To harvest, use a sharp knife to cut the head off at the base of the plant. Leave the outer leaves intact; they can sometimes produce smaller side shoots later in the season.

As our first frosts approach in early September, keep a close eye on the weather. If a frost is predicted, you can harvest any remaining heads, even if they're not quite fully mature. They'll still be delicious! You might also consider covering your plants with a frost blanket to extend the harvest a bit longer.

Here are some common cabbage problems we face 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: Similar to cabbage worms, but these caterpillars move in a looping motion. They also chew holes in leaves.
• What causes it: Larvae of a different type of moth.
• How to fix/prevent it: Similar to cabbage worms, Bt spray and row covers are effective. Handpicking also works.

Splitting

• What it looks like: The cabbage head cracks open.
• What causes it: Inconsistent watering. A period of drought followed by heavy watering causes the head to swell too quickly.
• How to fix/prevent it: Maintain consistent soil moisture. Water deeply and regularly, especially during dry spells. Mulch around the plants to help retain moisture.

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 stress cabbage plants, making them more susceptible to pests and diseases. Low humidity means we need to be diligent about watering, but it also reduces the risk of fungal diseases. The dry climate also means that pests like cabbage worms can thrive if we don't stay vigilant.

Companion planting can be a great way to improve your cabbage crop.

Good companions include green beans, celery, onion, potato, and dill. Green beans fix nitrogen in the soil, which benefits cabbage. Celery repels cabbage white butterflies. Onions deter many pests. Potatoes don't directly benefit cabbage, but they don't compete for nutrients and can help break up the soil. Dill attracts beneficial insects that prey on cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, and peppers. Tomatoes and strawberries can stunt cabbage growth. Peppers can attract similar pests, increasing the risk of infestation. These plants compete for similar resources and can create an unfavorable environment for your cabbage.