Cabbage in Zone 3A — Mountain West

Cabbage might not be the first thing that comes to mind for high altitude gardening, but its cool-season hardiness makes it a surprisingly rewarding crop here in the Mountain West. The crisp texture and slightly sweet flavor that develop in our cool nights are unbeatable, and it’s incredibly versatile in the kitchen, from slaws to stir-fries. Plus, there's real satisfaction in harvesting a big, beautiful cabbage head you grew yourself, right before the snow flies.

Our short growing season and alkaline soil definitely present challenges, but with careful timing and a few tricks, you can absolutely grow delicious cabbage in your Mountain garden. With our 96-day growing season, starting seeds indoors is key to success.

To get a jump start on the season, start your cabbage seeds indoors from late March through mid April. This gives them about 6 weeks to get established before transplanting, which is crucial in our short growing season. Use seed trays or small pots filled with a good quality seed starting mix.

Keep the soil consistently moist, and consider bottom watering to prevent damping off. Place the trays in a warm location, ideally around 70°F, and provide plenty of light. A sunny south-facing window can work, but supplemental grow lights are even better, especially with our intense spring sun.

Remember, spring arrives late here. Be patient, and don’t rush to put your seedlings outside before the danger of frost has passed.

Transplant your cabbage seedlings outdoors from mid May through mid June, once the soil has warmed up a bit and the risk of hard frost is minimal. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. Start with a couple of hours of shade and increase the time and sun exposure each day.

Plant them 12-18 inches apart in rows. Even in late spring, our weather can be unpredictable. Keep an eye on the forecast and be prepared to cover your young plants if a late frost threatens.

Cabbage needs consistent moisture to grow well, but overwatering can be just as detrimental as underwatering, especially with our alkaline soil. Aim to keep the soil evenly moist, but not soggy. During the warmer months, you'll likely need to water deeply a couple of times a week.

Use the finger test: stick your finger into the soil about 2 inches deep. If it feels dry, it’s time to water. In general, give your cabbage plants about 1-1.5 inches of water per week, either from rain or irrigation. Water at the base of the plants rather than overhead to minimize fungal diseases, which can still occur even in our low humidity.

Wilting leaves indicate underwatering, while yellowing lower leaves can signal overwatering. A layer of organic mulch, like straw or compost, will help retain moisture, suppress weeds, and regulate soil temperature.

You can expect your first cabbage harvest from late July through mid September, about 70 days after transplanting. The best indicator of ripeness is the firmness of the head. Gently squeeze the cabbage head; it should feel solid and dense. It should also be close to the full size for the variety you're growing.

To harvest, use a sharp knife to cut the head off at the base of the plant, leaving a few outer leaves intact. Don't wait too long to harvest, as cabbage heads can split if they become overmature, especially after a heavy rain.

As the first frost approaches in early September, harvest any remaining mature heads. Even if they're not quite as large as you'd like, they'll still be delicious. You can also try covering your plants with a blanket or row cover to extend the harvest a bit longer.

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

Cabbage Worms

• What it looks like: Smooth green caterpillars chewing holes in leaves, leaving dark green droppings behind. White butterflies fluttering around your plants.
• What causes it: Larvae of white cabbage butterflies.
• 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 irregular holes in the leaves.
• What causes it: Cabbage looper moths lay their eggs on cabbage plants.
• How to fix/prevent it: Use Bt spray or insecticidal soap. Handpick loopers. Attract 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 spurts.
• How to fix/prevent it: Provide consistent moisture. Avoid over-fertilizing. Harvest heads as soon as they are mature.

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 dry climate can actually help reduce the incidence of some fungal diseases in cabbage, but the intense sun can stress plants if they're not properly watered. Hail can also be a major issue, so consider using row covers or netting for protection.

Companion planting can be a great way to improve your cabbage crop. Green beans are good companions because they fix nitrogen in the soil, which benefits cabbage. Celery is said to deter cabbage white butterflies, while onions and dill can help repel other pests. Potatoes also make good companions, as they don’t compete for the same nutrients.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and peppers can attract some of the same pests that bother cabbage, while strawberries can inhibit cabbage growth.