Fertilizer for Geraniums: NPK Guide and Application Rates
Geraniums (Pelargonium) are consistent feeders that produce non-stop blooms from spring through frost with regular fertilization. Penn State Extension recommends feeding container geraniums every 2 weeks with a water-soluble fertilizer or incorporating slow-release granules at planting. In-ground geraniums need less frequent feeding due to access to soil nutrients. Yellow lower leaves often indicate nutrient deficiency or overwatering rather than disease.
Quick Reference
What NPK Ratio is Best for Geraniums?
The recommended NPK ratio for geraniums is 10-10-10. A balanced 10-10-10 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Geraniums NPK needs shift at each growth stage. Balanced formula for transplants and young starts during the Seedling phase, then higher phosphorus for continuous bloom production once flowering begins.
NPK by Growth Stage for Geraniums
| 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 transplants and young starts |
| Vegetative | 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 branching and leaf development |
| 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 | Higher phosphorus for continuous bloom production |
| Fruiting | 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 maintenance through late season |
When Should You Fertilize Geraniums?
In zone 3, start fertilizing geraniums in June. In zone 10, begin as early as January. Apply every 2 weeks through the growing season.
Which Zones Can Grow Geraniums?
Geraniums grows in USDA zones 3 through 10, spanning a 8-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 3 | June |
| Zone 4 | May |
| Zone 5 | May |
| Zone 6 | April |
| Zone 7 | March |
| Zone 8 | March |
| Zone 9 | February |
| Zone 10 | January |
What Are the Best Fertilizer Products for Geraniums?
Look for products with an NPK close to 10-10-10. Miracle-Gro All Purpose is the most popular choice among home gardeners for geraniums.
- Miracle-Gro All Purpose
- Osmocote Smart-Release
- Jack's Classic All Purpose
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Geraniums
The most popular container flower; feed every 2 weeks with liquid fertilizer or use slow-release granules at planting
Common Fertilizing Mistakes with Geraniums
- Overwatering and over-fertilizing simultaneously, which causes edema (corky bumps on leaf undersides).
- Using high-nitrogen fertilizer, which promotes leaf growth over flower production.
- Neglecting to deadhead, which signals the plant to stop producing new blooms.
- Fertilizing dry soil, which can cause root burn; always water before liquid fertilizer application.
Tips for Fertilizing Geraniums
- Feed container geraniums every 2 weeks with half-strength water-soluble fertilizer.
- Slow-release granular fertilizer at planting provides 3-4 months of consistent nutrition.
- Deadhead spent blooms to redirect energy from seed production to new flower development.
- Reduce feeding by half in late summer if plants become leggy; they may benefit from pinching instead.
Organic Fertilizer Alternatives for Geraniums
Sources
Source:Clemson HGIC - GeraniumLast updated: