Fertilizer for Broccoli: NPK Guide and Application Rates
Broccoli is a heavy-feeding brassica that demands consistent nitrogen to produce large, tight heads. The vegetative growth phase is especially critical since the size of the plant directly determines the size of the head. Side-dress with nitrogen when plants are 6 inches tall.
Quick Reference
What NPK Ratio is Best for Broccoli?
The recommended NPK ratio for broccoli is 10-10-10. A balanced 10-10-10 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Broccoli NPK needs shift at each growth stage. Balanced starter for transplants during the Seedling phase, then balanced feed as heads begin to form once flowering begins.
NPK by Growth Stage for Broccoli
| Growth Stage | NPK Ratio | Notes |
|---|---|---|
| Seedling | 10N 10P 10K N 10% Nitrogen: leaf and stem growth P 10% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Balanced starter for transplants |
| Vegetative | 20N 10P 10K N 20% Nitrogen: leaf and stem growth P 10% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Heavy nitrogen for large head development |
| Flowering | 10N 10P 10K N 10% Nitrogen: leaf and stem growth P 10% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Balanced feed as heads begin to form |
| Fruiting | 5N 10P 10K N 5% Nitrogen: leaf and stem growth P 10% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Reduce nitrogen once main head is harvested to support side shoots |
When Should You Fertilize Broccoli?
In zone 3, start fertilizing broccoli in May. In zone 10, begin as early as January. Apply every 3 weeks through the growing season.
Which Zones Can Grow Broccoli?
Broccoli grows in USDA zones 3 through 10, spanning a 8-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 3 | May |
| Zone 4 | May |
| Zone 5 | April |
| Zone 6 | March |
| Zone 7 | March |
| Zone 8 | February |
| Zone 9 | January |
| Zone 10 | January |
What Are the Best Fertilizer Products for Broccoli?
Look for products with an NPK close to 10-10-10. Espoma Garden-tone is the most popular choice among home gardeners for broccoli.
- Espoma Garden-tone
- Miracle-Gro Performance Organics Edibles
- Down to Earth Bio-Fish
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Broccoli
Broccoli in containers (5+ gallons) needs feeding every 2 weeks with nitrogen-rich liquid fertilizer
Common Fertilizing Mistakes with Broccoli
- Insufficient nitrogen results in small, loose, premature heads
- Planting in warm weather (above 80F) causes bolting regardless of fertilizer
- Skipping boron supplementation causes hollow stems and brown, corky patches
Tips for Fertilizing Broccoli
- Side-dress with nitrogen-rich fertilizer when plants reach 6 inches tall
- After harvesting the main head, continue feeding to encourage large side shoots
- Add boron (from borax) at 1 tablespoon per 100 feet of row to prevent hollow stems
Organic Fertilizer Alternatives for Broccoli
Sources
Source:Clemson University ExtensionLast updated: