Cabbage in Zone 7B — Desert Southwest

Cabbage is a rewarding crop to grow in our Desert Southwest gardens. Nothing beats the taste of fresh, homegrown cabbage in slaws, stir-fries, or even stuffed cabbage rolls. Plus, it's incredibly versatile in the kitchen, and there's real satisfaction in harvesting a beautiful, tightly-packed head that you nurtured yourself.

Our extreme summer heat can be a concern for many crops, but with careful timing, you can enjoy a successful spring cabbage harvest before the worst of the heat hits. Our long 245-day growing season gives you plenty of time to get it done if you start early.

To get a head start on your cabbage crop, start seeds indoors from mid January through early February. This gives the seedlings about six weeks to develop before transplanting. Use seed trays or small pots filled with a good quality seed-starting mix.

Keep the soil consistently moist, and consider bottom watering to avoid damping off and encourage strong root growth. Place the trays in a warm location, ideally around 70°F, and provide plenty of light – a grow light works wonders. Remember, our spring is very early here, so starting indoors is essential for a spring harvest.

Transplant your cabbage seedlings outdoors in early to late March, once they have a few sets of true leaves and the weather has settled. Before transplanting, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the stronger sunlight and temperature fluctuations.

Space the plants 12-18 inches apart in well-drained soil. Even in March, be mindful of potential temperature swings. If a late frost is predicted, cover the seedlings with frost cloth to protect them.

Cabbage needs consistent moisture to thrive, but overwatering can be just as detrimental. In our arid Desert Southwest climate, maintaining the right balance is key. During the spring growing season, water deeply about 1-2 inches per week, depending on rainfall.

Use the finger test to check soil moisture – if the top two inches of soil feel dry, it's time to water. Water at the base of the plants to avoid wetting the leaves, which can encourage fungal diseases in our sometimes humid monsoon season. Signs of underwatering include wilting and stunted growth, while yellowing leaves can signal overwatering.

As we approach the hotter months, increase watering frequency as needed, but always allow the soil surface to dry out slightly between waterings. A layer of organic mulch, such as straw or wood chips, can help retain soil moisture and regulate soil temperature. Remember, heavy watering after a dry spell can cause the heads to split, so maintain consistent moisture levels as much as possible.

You can expect to harvest your cabbage from early May through late June, about 70 days after transplanting. The best way to tell if a cabbage head is ready to harvest is to gently squeeze it. A ripe head will feel firm and solid.

Also, make sure it has reached the full size expected for the variety you planted. To harvest, use a sharp knife to cut the head at the base of the plant. As our first frost typically arrives around mid- November, any late-maturing heads can be harvested and used for fermentation or storage.

Here are some common problems you might encounter growing cabbage in our region:

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 loopers move in a distinctive looping motion. They also chew holes in leaves.
• What causes it: Cabbage looper moths lay eggs on cabbage and other brassica plants.
• How to fix/prevent it: Bt spray is effective. Handpick loopers. Encourage beneficial insects like parasitic wasps and lacewings.

Splitting

• What it looks like: The cabbage head cracks or splits open.
• What causes it: Inconsistent watering, especially heavy watering after a dry period. The rapid uptake of water causes the head to expand too quickly.
• How to fix/prevent it: Maintain consistent soil moisture. Water deeply but less frequently. Mulch around plants to retain moisture. Harvest heads as soon as they are mature to prevent over-ripening and 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.

Desert Southwest Specific Challenges: Our extreme heat can stress cabbage plants, making them more susceptible to pests and diseases. The arid air can also lead to rapid soil drying, so consistent watering is crucial. While monsoon moisture can be beneficial, it can also create conditions favorable for fungal diseases if air circulation is poor. Alkaline soil is common in our region, so amend with compost to improve soil structure and drainage, and consider adding sulfur to lower the pH slightly.

Companion planting can be a great way to help your cabbage thrive. Green beans are good companions because they fix nitrogen in the soil, which benefits cabbage. Celery helps repel cabbage white butterflies, reducing cabbage worm infestations. Onions deter cabbage root flies, while potatoes help to break up the soil and improve drainage. Dill also attracts beneficial insects that prey on cabbage pests.

Avoid planting cabbage near tomatoes, strawberries, or peppers. Tomatoes and strawberries compete for nutrients, while peppers can attract cabbage white butterflies.