Fertilizer for Petunias: NPK Guide and Application Rates
Petunias are among the heaviest-feeding annual flowers, especially Wave and Supertunia types in hanging baskets. In containers, they can exhaust soil nutrients within two weeks and require frequent, consistent feeding to maintain their prolific bloom display all summer.
Quick Reference
What NPK Ratio is Best for Petunias?
The recommended NPK ratio for petunias is 10-10-10. A balanced 10-10-10 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Petunias NPK needs shift at each growth stage. Balanced starter for transplants during the Seedling phase, then phosphorus boost for heavy blooming once flowering begins.
NPK by Growth Stage for Petunias
| 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 | 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 for bushy, compact growth |
| Flowering | 10N 15P 10K N 10% Nitrogen: leaf and stem growth P 15% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Phosphorus boost for heavy blooming |
| Fruiting | 10N 15P 10K N 10% Nitrogen: leaf and stem growth P 15% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Continue bloom-boosting through the season |
When Should You Fertilize Petunias?
In zone 3, start fertilizing petunias in June. In zone 11, begin as early as January. Apply every 2 weeks through the growing season.
Which Zones Can Grow Petunias?
Petunias grows in USDA zones 3 through 11, spanning a 9-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 3 | June |
| Zone 4 | May |
| Zone 5 | May |
| Zone 6 | April |
| Zone 7 | April |
| Zone 8 | March |
| Zone 9 | February |
| Zone 10 | February |
| Zone 11 | January |
What Are the Best Fertilizer Products for Petunias?
Look for products with an NPK close to 10-10-10. Miracle-Gro Bloom Booster is the most popular choice among home gardeners for petunias.
- Miracle-Gro Bloom Booster
- Jack's Classic Petunia Feed
- Espoma Flower-tone
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Petunias
Container and hanging basket petunias need weekly liquid fertilization; they are extremely heavy feeders in pots
Common Fertilizing Mistakes with Petunias
- Skipping fertilization in hanging baskets causes petunias to stop blooming within weeks
- Overhead watering causes botrytis and petal spotting on petunia flowers
- Not cutting back mid-season leads to leggy, bare-stemmed plants with flowers only at the tips
Tips for Fertilizing Petunias
- Feed Wave and Supertunia types every 7-10 days in containers; they are exceptionally heavy feeders
- Cut back leggy petunias by one-third mid-season and increase feeding to trigger a fresh flush of growth
- Use iron-supplemented fertilizer if leaves yellow while veins stay green (iron chlorosis)
Organic Fertilizer Alternatives for Petunias
Sources
Source:Clemson Cooperative ExtensionLast updated: