Fertilizer for Begonias: NPK Guide and Application Rates
Begonias are light to moderate feeders with sensitive roots that respond best to frequent, diluted fertilizer applications. The University of Minnesota Extension recommends half-strength liquid fertilizer every 2 weeks during the growing season. Begonia roots are easily burned by full-strength fertilizer, so the key principle is 'weakly, weekly' -- dilute and apply frequently rather than strong infrequent doses. Tuberous begonias have slightly higher potassium needs than wax or rex types.
Quick Reference
What NPK Ratio is Best for Begonias?
The recommended NPK ratio for begonias is 10-10-10. A balanced 10-10-10 feeds all three macronutrients equally, which works well when soil tests show no single deficiency.
Begonias NPK needs shift at each growth stage. Balanced formula for young transplants at quarter strength during the Seedling phase, then higher phosphorus promotes continuous flowering once flowering begins.
NPK by Growth Stage for Begonias
| 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 young transplants at quarter strength |
| 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 during active growth period |
| 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 promotes continuous flowering |
| 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 feeding through season's end |
When Should You Fertilize Begonias?
In zone 3, start fertilizing begonias in June. In zone 10, begin as early as February. Apply every 2 weeks through the growing season.
Which Zones Can Grow Begonias?
Begonias grows in USDA zones 3 through 10, spanning a 8-zone range.
Fertilization Start by Zone
| Zone | Start Month |
|---|---|
| Zone 3 | June |
| Zone 4 | June |
| Zone 5 | May |
| Zone 6 | May |
| Zone 7 | April |
| Zone 8 | March |
| Zone 9 | March |
| Zone 10 | February |
What Are the Best Fertilizer Products for Begonias?
Look for products with an NPK close to 10-10-10. Osmocote Smart-Release is the most popular choice among home gardeners for begonias.
- Osmocote Smart-Release
- Miracle-Gro All Purpose
- Jack's Classic
Prices vary by retailer and region. Check current pricing before purchasing.
Container and Raised Bed Adjustments for Begonias
Ideal container plants; feed every 2 weeks with diluted liquid fertilizer at half the label rate
Common Fertilizing Mistakes with Begonias
- Applying full-strength fertilizer, which burns the fine, shallow root system of begonias.
- Fertilizing rex begonias with bloom booster; they are grown for foliage and need balanced nutrition.
- Letting fertilizer salts build up in containers; flush pots with clear water monthly.
- Fertilizing stressed or wilted plants; always rehydrate first, then feed the following day.
Tips for Fertilizing Begonias
- Use fertilizer at half the label rate to avoid burning begonia's sensitive root system.
- Feed every 2 weeks during active growth; reduce to monthly in winter for houseplant begonias.
- Tuberous begonias benefit from higher potassium as tubers begin forming in late summer.
- Rex begonias are foliage plants and prefer balanced formulas rather than bloom boosters.
Organic Fertilizer Alternatives for Begonias
Sources
Source:Clemson University ExtensionLast updated: