Cabbage (Brassica oleracea var. capitata) is a popular cool-season vegetable appreciated for its versatility and nutritional value. Growing this crop directly from seed allows gardeners to select from a wider range of heirloom and hybrid varieties than typically available as nursery starts. Starting seeds at home is also a cost-effective method for producing a large harvest and ensures plants are robust and adapted to local climate conditions.
Timing and Starting Seeds Indoors
The success of a cabbage crop depends on proper timing, as it thrives in cooler weather and bolts in prolonged heat. For a spring harvest, start seeds indoors four to six weeks before the last expected frost. For a fall crop, which often produces sweeter heads, start seeds eight to ten weeks before the first anticipated fall frost.
Use sterilized seed-starting mix in trays or small pots to minimize the risk of fungal diseases. Sow seeds shallowly, covering them with about a quarter-inch of medium. Cabbage seeds require a consistent temperature between 65°F and 75°F for optimal germination within four to ten days.
After emergence, seedlings need strong, consistent light (14 to 16 hours daily under grow lights) to prevent them from becoming tall and spindly (etiolation). Keep the soil damp but never waterlogged to support active root development.
Once seedlings develop their first true leaves, thin them to one plant per cell or transplant them into slightly larger containers. This provides space for root expansion before moving them outside. A heat mat can speed up germination but should be removed once seedlings sprout to encourage sturdier stem growth.
Hardening Off and Transplanting
Moving indoor seedlings directly into the garden causes significant shock. Hardening off is a gradual acclimation process that introduces young plants to outdoor conditions like wind, intense sun, and fluctuating temperatures. Start this process seven to ten days before transplanting.
Begin by placing seedlings outdoors in a protected, shaded location for a few hours daily. Each subsequent day, increase exposure duration and gradually move them into areas receiving more direct sunlight and wind. This slow transition toughens the plant’s cell walls.
Prepare the garden bed by incorporating organic matter to create loamy soil with good drainage. Cabbage prefers a slightly acidic to neutral soil pH (6.0 to 7.5). When transplanting, dig a hole large enough for the root ball and set the seedling deep so the lowest true leaves are just above the soil line.
Proper spacing is necessary for full head development and good air circulation, which prevents fungal issues. Space plants 12 to 24 inches apart in rows, depending on the variety. Firm the soil around the base of each transplant and water immediately to settle the soil and reduce stress.
Ongoing Care and Pest Control
Cabbage is a heavy feeder, requiring consistently available nutrients, particularly nitrogen, to form large, dense heads. Apply a balanced, nitrogen-rich fertilizer every four to six weeks to support the rapid vegetative growth phase. Consistent soil moisture is also necessary, as inconsistent watering can lead to splitting heads or bitter flavor.
Applying organic mulch helps regulate soil temperature, retain moisture, and suppress weeds. Since cabbage plants have shallow root systems, cultivating the soil to remove weeds should be done carefully and lightly. Regular, deep watering, especially during dry spells, supports the formation of a solid head.
Pest management is crucial, as many insects find the leaves appealing. Cabbage worms and cabbage loopers (larvae of white butterflies and moths) are common defoliators. Monitor the undersides of leaves for their small, yellowish eggs, allowing for early intervention through handpicking.
Floating row covers are an effective preventative measure, physically excluding egg-laying adult insects. For existing infestations, use Bacillus thuringiensis (Bt), a biological control agent. Bt is a naturally occurring bacterium that paralyzes the caterpillars’ digestive system but is harmless to beneficial insects and humans. Aphids cluster on new growth and can be managed with a strong jet of water or insecticidal soap.
Harvesting Cabbage
Harvesting at the right time ensures the best texture and flavor, preventing heads from becoming overripe or splitting. Cabbage heads are ready when they feel solid and firm when gently squeezed, indicating the inner leaves have fully compacted. Timing typically occurs 60 to 100 days after transplanting, depending on the variety.
To harvest the main head, use a sharp knife to cut through the stem just below the lowest layer of marketable leaves. Leaving the stalk and a few outer leaves intact encourages a secondary harvest. The remaining stalk often produces several small, loose sprouts that can be picked later.
Many varieties will generate new, smaller heads from the sides of the remaining stem tissue after the initial cut. While these secondary heads are smaller than the primary harvest, they offer an extended yield. Complete harvesting before prolonged hot weather, which can cause the heads to bolt or the flavor to become harsh.