Fertilizer for Hydrangeas: NPK Guide and Application Rates
Hydrangeas respond well to consistent spring and early summer feeding. Flower color on bigleaf hydrangeas (H. macrophylla) is determined by soil pH and aluminum availability, not directly by fertilizer NPK ratio, though the fertilizer you choose can influence pH over time.
Quick Reference
What NPK Ratio is Best for Hydrangeas?
The recommended NPK ratio for hydrangeas is 10-10-10. A balanced 10-10-10 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Hydrangeas NPK needs shift at each growth stage. Balanced feed for newly planted hydrangeas during the Seedling phase, then phosphorus encourages heavy bloom production once flowering begins.
NPK by Growth Stage for Hydrangeas
| 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 feed for newly planted hydrangeas |
| 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 | Nitrogen supports strong spring growth |
| Flowering | 10N 20P 10K N 10% Nitrogen: leaf and stem growth P 20% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Phosphorus encourages heavy bloom production |
| Fruiting | 0N 0P 10K N 0% Nitrogen: leaf and stem growth P 0% Phosphorus: roots and flowers K 10% Potassium: health and disease resistance Learn more about NPK | Potassium only in fall for winter hardiness |
When Should You Fertilize Hydrangeas?
In zone 3, start fertilizing hydrangeas in May. In zone 9, begin as early as February. Apply every 6 weeks through the growing season.
Which Zones Can Grow Hydrangeas?
Hydrangeas grows in USDA zones 3 through 9, spanning a 7-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 3 | May |
| Zone 4 | May |
| Zone 5 | April |
| Zone 6 | April |
| Zone 7 | March |
| Zone 8 | March |
| Zone 9 | February |
What Are the Best Fertilizer Products for Hydrangeas?
Look for products with an NPK close to 10-10-10. Espoma Holly-tone is the most popular choice among home gardeners for hydrangeas.
- Espoma Holly-tone
- Jobe's Hydrangea Fertilizer Spikes
- Miracle-Gro Shake 'n Feed Flowering Trees & Shrubs
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Hydrangeas
Feed container hydrangeas monthly with diluted liquid fertilizer from spring through midsummer; stop by August
Common Fertilizing Mistakes with Hydrangeas
- Fertilizing too late in summer promotes soft growth that winter-kills
- Using high-phosphorus fertilizer blocks aluminum uptake, preventing blue flowers
- Over-fertilizing causes leaf burn on the edges of hydrangea leaves
Tips for Fertilizing Hydrangeas
- For blue flowers, use acid-forming fertilizer and add aluminum sulfate to lower pH
- For pink flowers, use a balanced or slightly alkaline fertilizer and add lime
- Stop fertilizing by mid-July to allow canes to harden before winter
Organic Fertilizer Alternatives for Hydrangeas
Sources
Source:Clemson Cooperative ExtensionLast updated: