Cabbage in Zone 5A — Mountain West

Cabbage might seem like a basic vegetable, but when you grow it yourself here in the Mountain West, the flavor is outstanding. The cool nights even in summer concentrate sugars, giving you a sweetness you just can't find in store-bought heads. Plus, it’s incredibly versatile, from slaws to stir-fries, and there's nothing quite like the satisfaction of harvesting a perfect head you nurtured yourself.

Our high altitude gardening presents challenges, like intense sun and a short season, but Cabbage is a cool-season crop that thrives with proper timing. With our 138-day growing season, starting indoors and choosing the right varieties will set you up for success.

To get a head start on your Cabbage, begin sowing seeds indoors from early to late March. This gives them about 6 weeks to get established before transplanting. Use seed trays or small pots filled with a good seed-starting mix.

Keep the soil consistently moist (bottom watering works great to avoid damping off) and provide plenty of light – a grow light is ideal, especially with our late spring starts. Aim for a consistent temperature around 70°F for optimal germination. Remember, our spring weather can be unpredictable, so starting indoors gives your Cabbage seedlings the best chance.

Transplant your Cabbage seedlings outdoors from late April through late May, once the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the intense sun and cooler temperatures.

Space your plants 12-18 inches apart in rows. Be mindful of potential late frosts, especially in low-lying areas where cold air settles. Covering your young plants with horticultural fleece can provide extra protection if needed.

Cabbage needs consistent moisture, but avoid extremes. Here in the Mountain West, with our dry climate and low humidity, regular watering is crucial. Aim to keep the soil consistently moist, but not waterlogged.

A good rule of thumb is to water deeply once or twice a week, providing about 1-2 inches of water per week. Use the finger test: stick your finger about 2 inches 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 a concern here.

Signs of underwatering include wilting leaves and slow growth. Overwatering can lead to root rot, so make sure the soil drains well. Mulching around your Cabbage plants with straw or wood chips helps retain moisture and regulate soil temperature, which is especially important in our dry climate.

You can expect your first Cabbage harvest from early July through late August, about 70 days after transplanting. The key sign of ripeness is a firm, solid head. When you squeeze the head, it should feel dense and compact.

To harvest, use a sharp knife to cut the head off at the base of the plant, leaving a few outer leaves intact. If you're approaching our typical first frost in late September and still have some smaller heads, you can try covering them with a blanket or horticultural fleece to extend the season a bit longer. However, fully mature heads should be harvested before a hard freeze.

Here are some common Cabbage problems we see in the Mountain West:

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing irregular holes in leaves, leaving dark green droppings. You might also see white butterflies fluttering around.
• What causes it: Larvae of those white cabbage butterflies. They can have multiple generations during our relatively short warm season.
• How to fix/prevent it: Bt spray is very effective. Floating row covers from transplanting can prevent the butterflies from laying eggs. Handpicking works for small infestations. Interplant with aromatic herbs like thyme and sage to deter the butterflies.

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: Another type of caterpillar that feeds on brassicas.
• How to fix/prevent it: Similar to cabbage worms, Bt spray and row covers are effective. Check plants regularly and remove loopers by hand.

Splitting

• What it looks like: The Cabbage head cracks open.
• What causes it: Inconsistent watering, especially heavy watering after a dry spell. The rapid water uptake causes the head to expand too quickly.
• How to fix/prevent it: Provide consistent moisture throughout the growing season. Mulch to help retain moisture. If a dry spell is followed by rain, consider harvesting mature heads preventatively.

Clubroot

• What it looks like: Stunted growth, wilting in the afternoon heat, and yellowing leaves. When you dig up the plant, the roots are swollen and distorted.
• What causes it: A soil-borne pathogen that can persist for years. It favors acidic, wet soil.
• How to fix/prevent it: This is tough. Raise the 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 them!). Start transplants in sterile mix.

Mountain West Specific Challenges: Our intense sun can sometimes stress young Cabbage plants, so providing some afternoon shade with row covers or shade cloth during the hottest part of the day can be helpful. The alkaline soil common in our region can also affect nutrient availability, so amending with compost and using a fertilizer formulated for vegetables can help. While low humidity reduces disease pressure, it also means you need to be extra vigilant about watering. Finally, hail can devastate Cabbage, so be prepared to cover your plants if a hailstorm is predicted.

Good companions for Cabbage include green beans, celery, onions, potatoes, and dill. Green beans fix nitrogen in the soil, benefiting Cabbage's growth. Celery can deter cabbage white butterflies. Onions and dill repel various pests. Potatoes don't directly benefit Cabbage, but they don't compete for the same nutrients and can be planted nearby.

Avoid planting Cabbage near tomatoes, strawberries, or peppers. Tomatoes and peppers are heavy feeders and can compete with Cabbage for nutrients. Strawberries can attract slugs and snails, which can also damage Cabbage. In our short growing season, you want to give your Cabbage every advantage it can get!