Fertiliser for Cabbage Plants: How to Grow, Feed & Maximise Head Size in Australian Gardens

Cabbage (Brassica oleracea var. capitata) is a nutrient-demanding cool-season crop that thrives with the right balance of nitrogen, phosphorus, and potassium. Whether you’re growing tight drumheads, savoy varieties, or vibrant red cabbage, understanding how to feed and care for these leafy vegetables is key to producing large, compact, and flavourful heads throughout the growing season.

Cabbage Plant Basics – Growth Habit, Structure & Lifecycle

Cabbage is a leafy biennial grown annually for its dense, rounded head formed by overlapping leaves. It prefers full sun, cool weather, and fertile, well-drained soil enriched with organic matter or a balanced NPK fertiliser. Varieties like sugarloaf, red cabbage, and green drumhead are commonly grown across Australia’s temperate zones during late summer to winter. Key characteristics:

Botanical name: Brassica oleracea var. capitata
Common names: Cabbage, Drumhead, Savoy, Red cabbage
Growth habit: Compact rosette of overlapping leaves forming a tight central head
Sunlight: Full sun (6–8 hours daily)
Soil: Rich, well-drained loam; pH 6.0–7.0

Cabbage takes between 10 to 14 weeks to mature depending on the variety and climate. Seedlings are typically transplanted 3–4 weeks after germination, and the plant transitions through rapid leaf production before forming a head. Fertiliser application is essential at every stage, as the plant requires ample nitrogen early on, and more potassium during head development. With proper feeding, cabbage can yield firm, market-quality heads that store well and resist splitting.

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How to Grow & Care for Cabbage Plants in Australia

Cabbage performs best in cool climates and is ideal for planting in late summer, autumn, and early spring across most parts of Australia. Consistent moisture, correct spacing, and a proper fertiliser regimen are vital for success. Key growing conditions include:

Light: Cabbage needs full sun to grow dense, well-formed heads. Avoid partial shade, as it leads to loose leaf growth and delayed heading.
Soil: Prepare the bed with a fine-tilled, well-drained loam. Incorporate compost or well-rotted manure before planting, and test pH to maintain levels between 6.0–7.0.
Spacing: Space plants 30–40 cm apart in rows 45–60 cm wide to allow proper head development and airflow.
Watering: Maintain consistent moisture, especially during head formation. Infrequent or shallow watering can lead to splitting, bolting, or bitter flavour.
Pests: Watch for cabbage white butterfly, aphids, and caterpillars. Use exclusion netting or companion planting (e.g. nasturtiums) to deter infestations.

Maintenance tips:

Mulch: Apply straw or sugarcane mulch around the base to retain moisture and suppress weeds.
Weeding: Hand-weed carefully to avoid disturbing shallow roots.
Crop rotation: Avoid planting cabbage in the same bed for consecutive years to prevent soil-borne disease buildup like clubroot.

Cabbage is a heavy feeder. For optimal results, start fertilising 1–2 weeks after transplanting and continue at regular intervals. Leaf colour and size are good indicators of nutrient sufficiency—pale leaves or stunted growth usually signal a nitrogen or magnesium deficiency.

Understanding Cabbage Fertiliser: What to Use & When to Feed

As a nutrient-intensive vegetable, cabbage requires a multi-stage feeding plan that aligns with its lifecycle. Each growth phase has different nutrient priorities, and a well-structured fertiliser strategy will help form dense, flavourful heads while preventing disorders like hollow stem or tip burn. Stage-by-stage fertilising guide:

Early growth (Weeks 1–4): Apply a balanced fertiliser like NPK 20-20-20 every 10–14 days. This supports strong root development and leafy growth without overwhelming the young plant.
Mid-stage (Weeks 5–8): Maintain nitrogen-rich feeding for continued leaf expansion. Use a complete liquid formula with trace elements such as calcium and magnesium to avoid internal disorders.
Heading stage (Weeks 9+): Reduce nitrogen slightly and increase potassium using a formula like NPK 4-18-38. This encourages head density, disease resistance, and improved post-harvest life.

Common mistakes to avoid:

Applying too much nitrogen late in the cycle — leads to loose heads and reduced shelf life
Feeding dry soil — always water before fertilising to avoid root burn
Skipping calcium and boron — deficiencies result in hollow stems and internal browning

For best results in Australian gardens, use a high-quality, water-soluble fertiliser tailored for vegetables. We recommend starting your crop with CompleteGrow’s All Purpose NPK 20-20-20 Liquid Fertiliser, then switching to CompleteGrow NPK 4-18-38 + CaMg once heading begins. Both blends supply essential micronutrients and are ideal for soil-grown or raised bed cabbage crops.