Fertilizer for Boxwood: NPK Guide and Application Rates
Boxwood shrubs are moderate feeders that benefit from annual fertilization to maintain their signature dense, evergreen foliage. The University of Maryland Extension recommends applying fertilizer in late fall or early spring based on soil test results. Boxwood leaf analysis, rather than appearance alone, is the most reliable way to identify nutrient deficiencies. Bronze or yellow winter color is normal for some varieties and not necessarily a sign of nutrient stress.
Quick Reference
What NPK Ratio is Best for Boxwood?
The recommended NPK ratio for boxwood is 10-6-4. The nitrogen-forward 10-6-4 ratio drives leaf and stem development, which boxwood needs for photosynthesis and canopy growth.
Boxwood NPK needs shift at each growth stage. Balanced formula for newly planted boxwood during the Seedling phase, then boxwood bloom is insignificant; maintain consistent feeding once flowering begins.
NPK by Growth Stage for Boxwood
| 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 formula for newly planted boxwood |
| Vegetative | 10N 6P 4K N 10% Nitrogen: leaf and stem growth P 6% Phosphorus: roots and flowers K 4% Potassium: health and disease resistance Learn more about NPK | Moderate nitrogen for controlled, dense growth |
| Flowering | 10N 6P 4K N 10% Nitrogen: leaf and stem growth P 6% Phosphorus: roots and flowers K 4% Potassium: health and disease resistance Learn more about NPK | Boxwood bloom is insignificant; maintain consistent feeding |
| Fruiting | 10N 6P 4K N 10% Nitrogen: leaf and stem growth P 6% Phosphorus: roots and flowers K 4% Potassium: health and disease resistance Learn more about NPK | No seasonal change needed; stop feeding by September |
When Should You Fertilize Boxwood?
In zone 5, start fertilizing boxwood in April. In zone 9, begin as early as February. Apply every 8 weeks through the growing season.
Which Zones Can Grow Boxwood?
Boxwood grows in USDA zones 5 through 9, spanning a 5-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 5 | April |
| Zone 6 | April |
| Zone 7 | March |
| Zone 8 | March |
| Zone 9 | February |
What Are the Best Fertilizer Products for Boxwood?
Look for products with an NPK close to 10-6-4. Espoma Plant-tone is the most popular choice among home gardeners for boxwood.
- Espoma Plant-tone
- Holly-tone
- 10-6-4
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Boxwood
Commonly grown in containers for formal gardens; feed twice per year with slow-release granular
Common Fertilizing Mistakes with Boxwood
- Shearing boxwood into tight shapes without providing adequate nutrition to support regrowth.
- Confusing normal winter bronzing with nutrient deficiency; many varieties naturally bronze in cold.
- Applying acidifying fertilizers that lower pH below boxwood's preferred range.
- Deep cultivation around boxwood that damages the shallow root system.
Tips for Fertilizing Boxwood
- Apply granular fertilizer in late fall or early spring, broadcasting under the canopy.
- Maintain soil pH between 6.5-7.0; boxwood prefers slightly alkaline conditions unlike azaleas.
- Use soil or leaf tissue tests to identify actual deficiencies before applying extra nutrients.
- Mulch with 2 inches of organic material, keeping it away from stems to prevent stem rot.
Organic Fertilizer Alternatives for Boxwood
Sources
Source:University of Maryland ExtensionLast updated: