Fertilizer for Kale: NPK Guide and Application Rates
Kale is a cold-hardy brassica that produces sweeter, more tender leaves after a frost. It is a moderate feeder that benefits from consistent nitrogen for continuous leaf production throughout its long growing season, which can extend from early spring through late fall in many climates.
Quick Reference
What NPK Ratio is Best for Kale?
The recommended NPK ratio for kale is 10-10-10. A balanced 10-10-10 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Kale NPK needs shift at each growth stage. Balanced starter for transplants or direct seeding during the Seedling phase, then balanced feed; harvest before bolting once flowering begins.
NPK by Growth Stage for Kale
| 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 or direct seeding |
| Vegetative | 15N 5P 10K N 15% Nitrogen: leaf and stem growth P 5% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Nitrogen-forward for continuous leaf production |
| 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; harvest before bolting |
| Fruiting | 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 | Not applicable; kale is a leaf-harvest crop |
When Should You Fertilize Kale?
In zone 3, start fertilizing kale in May. In zone 10, begin as early as January. Apply every 4 weeks through the growing season.
Which Zones Can Grow Kale?
Kale grows in USDA zones 3 through 10, spanning a 8-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 3 | May |
| Zone 4 | April |
| 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 Kale?
Look for products with an NPK close to 10-10-10. Espoma Garden-tone is the most popular choice among home gardeners for kale.
- Espoma Garden-tone
- Neptune's Harvest Fish & Seaweed
- Dr. Earth Vegetable Garden Fertilizer
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Kale
Container kale benefits from biweekly liquid feeding with nitrogen-rich fertilizer; harvest outer leaves regularly
Common Fertilizing Mistakes with Kale
- Under-feeding produces small, tough, bitter leaves that are unappetizing
- Planting only in spring and missing the superior fall crop
- Harvesting the center growing point kills the plant instead of allowing continued production
Tips for Fertilizing Kale
- Harvest outer leaves first and let the center continue growing for a cut-and-come-again harvest
- Apply a nitrogen side-dressing every 4 weeks during active growth
- Frost exposure actually improves kale flavor by converting starches to sugars
Organic Fertilizer Alternatives for Kale
Sources
Source:Clemson University ExtensionLast updated: