Fertilizer for Tomatoes: NPK Guide and Application Rates
Tomatoes are heavy feeders that require consistent fertilization throughout the growing season. The key is shifting from nitrogen-heavy feeding during vegetative growth to phosphorus and potassium-rich feeding once flowers appear.
Quick Reference
What NPK Ratio is Best for Tomatoes?
The recommended NPK ratio for tomatoes is 5-10-10. The phosphorus-heavy 5-10-10 ratio supports strong root systems and flower/fruit production in tomatoes.
Tomatoes NPK needs shift at each growth stage. Balanced feeding for establishment during the Seedling phase, then shift to phosphorus for bloom set once flowering begins.
NPK by Growth Stage for Tomatoes
| 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 feeding for establishment |
| Vegetative | 10N 5P 5K N 10% Nitrogen: leaf and stem growth P 5% Phosphorus: roots and flowers K 5% Potassium: health and disease resistance Learn more about NPK | Higher nitrogen for leaf growth |
| Flowering | 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 | Shift to phosphorus for bloom set |
| 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 | Maintain P and K for fruit development |
When Should You Fertilize Tomatoes?
In zone 4, start fertilizing tomatoes in June. In zone 10, begin as early as February. Apply every 3 weeks through the growing season.
Which Zones Can Grow Tomatoes?
Tomatoes grows in USDA zones 4 through 10, spanning a 7-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 4 | June |
| Zone 5 | May |
| Zone 6 | May |
| Zone 7 | April |
| Zone 8 | March |
| Zone 9 | March |
| Zone 10 | February |
What Are the Best Fertilizer Products for Tomatoes?
Look for products with an NPK close to 5-10-10. Espoma Tomato-tone is the most popular choice among home gardeners for tomatoes.
- Espoma Tomato-tone
- Miracle-Gro Tomato Plant Food
- Dr. Earth Home Grown
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Tomatoes
Fertilize container tomatoes every 2 weeks with half-strength liquid fertilizer
Common Fertilizing Mistakes with Tomatoes
- Over-fertilizing with nitrogen causes lush foliage but few tomatoes
- Not adding calcium leads to blossom end rot
- Fertilizing too close to the stem causes root burn
Tips for Fertilizing Tomatoes
- Stop nitrogen-heavy feeding once flowers appear to avoid all-leaf-no-fruit syndrome
- Add calcium (from lime or calcium nitrate) to prevent blossom end rot
- Side-dress with compost every 3-4 weeks during peak production
Organic Fertilizer Alternatives for Tomatoes
Sources
Source:Penn State ExtensionLast updated: