How to Fertilize Cabbage for Leaf Growth and Head Formation

Cabbage is a nutrient-hungry vegetable that requires balanced fertilization to thrive—from producing vigorous leafy growth to forming dense, tight heads. With over 30 years of growing experience, I’ve found that timing and type of fertilizer make a big difference in cabbage quality and yield. This guide covers how to fertilize cabbage effectively for both leaf and head development.

Table of Contents

Understanding Cabbage Nutrient Needs

Nitrogen (N): Supports leafy, lush growth early in the season.
Phosphorus (P): Encourages strong root development for healthy plants.
Potassium (K): Essential during head formation for firm, dense heads.

When and How to Fertilize

Pre-Plant Fertilization:
- Incorporate well-aged compost or balanced fertilizer (e.g., 10-10-10) into the soil before planting.
- This builds a nutrient-rich base for seedlings.
Side-Dressing During Leaf Growth:
- About 3–4 weeks after transplanting, apply a nitrogen-rich fertilizer (such as fish emulsion or blood meal).
- This boosts leafy growth essential for photosynthesis.
Fertilizing for Head Formation:
- When heads begin to form (typically 5–6 weeks after transplant), switch to a fertilizer higher in potassium (like kelp meal or sulfate of potash).
- This supports head firmness and size.

Tips for Effective Fertilizing

Water before and after applying fertilizer to reduce root burn and improve nutrient uptake.
Avoid over-fertilizing nitrogen late in the season to prevent loose heads and increased pest susceptibility.
Use organic fertilizers where possible to promote soil health.

My takeaway:
In my Sonoma Valley (Zone 9) garden, staggered fertilization timed to cabbage growth stages consistently produces large, sweet heads and strong, healthy plants. Paying attention to nutrient shifts from leafy growth to head formation is key to success.

Cabbage Fertilizing Schedule

Growth Stage	Timing	Fertilizer Type	Application Tips
Pre-Plant Soil Prep	Before planting	Balanced (10-10-10) or compost	Work into soil deeply for nutrient-rich base
Leaf Growth	3–4 weeks after transplanting	Nitrogen-rich (fish emulsion, blood meal)	Side-dress around plants; water in well
Head Formation	5–6 weeks after transplanting	Potassium-rich (kelp meal, sulfate of potash)	Apply carefully to avoid leaf burn
Late Season	1–2 weeks before harvest	Light feeding or none	Avoid excess nitrogen to prevent loose heads

Pro tip:
I always water thoroughly before and after fertilizing to ensure nutrients reach roots without causing fertilizer burn. Timing fertilizer with growth stages produces the best flavor and head density.