Fertilizer for Rosemary: NPK Guide and Application Rates
Rosemary is a Mediterranean herb adapted to poor, rocky, well-drained soil and requires very little fertilizer. It naturally thrives in low-nutrient conditions, and over-feeding is a leading cause of rosemary decline in home gardens. Proper drainage matters far more than nutrition.
Quick Reference
What NPK Ratio is Best for Rosemary?
The recommended NPK ratio for rosemary is 5-5-5. A balanced 5-5-5 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Rosemary NPK needs shift at each growth stage. Light balanced feed for new transplants only during the Seedling phase, then slight phosphorus increase supports flowering once flowering begins.
NPK by Growth Stage for Rosemary
| 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 | Light balanced feed for new transplants only |
| Vegetative | 5N 5P 5K N 5% Nitrogen: leaf and stem growth P 5% Phosphorus: roots and flowers K 5% Potassium: health and disease resistance Learn more about NPK | Very light spring feeding for established plants |
| Flowering | 5N 10P 5K N 5% Nitrogen: leaf and stem growth P 10% Phosphorus: roots and flowers K 5% Potassium: health and disease resistance Learn more about NPK | Slight phosphorus increase supports flowering |
| Fruiting | 0N 0P 0K N 0% Nitrogen: leaf and stem growth P 0% Phosphorus: roots and flowers K 0% Potassium: health and disease resistance Learn more about NPK | No feeding needed after midsummer |
When Should You Fertilize Rosemary?
In zone 7, start fertilizing rosemary in March. In zone 11, begin as early as January. Apply every 8 weeks through the growing season.
Which Zones Can Grow Rosemary?
Rosemary grows in USDA zones 7 through 11, spanning a 5-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 7 | March |
| Zone 8 | March |
| Zone 9 | February |
| Zone 10 | February |
| Zone 11 | January |
What Are the Best Fertilizer Products for Rosemary?
Look for products with an NPK close to 5-5-5. Espoma Garden-tone is the most popular choice among home gardeners for rosemary.
- Espoma Garden-tone
- Dr. Earth Herb Fertilizer
- Osmocote Smart-Release
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Rosemary
Container rosemary needs only 1-2 light feedings per year; overwintering indoors requires even less
Common Fertilizing Mistakes with Rosemary
- Over-fertilizing causes rapid, weak growth that is vulnerable to disease and cold damage
- Poor drainage causes root rot, which is the top killer of rosemary plants
- Overwintering indoors without reducing watering and feeding causes root rot
Tips for Fertilizing Rosemary
- A single light application of slow-release fertilizer in spring is sufficient for the entire year
- Ensure exceptional drainage; rosemary dies from wet roots far more often than from nutrient deficiency
- Prune regularly to encourage bushy growth and prevent woody, bare stems
Organic Fertilizer Alternatives for Rosemary
Sources
Source:Penn State ExtensionLast updated: