Best Tomato & Strawberry Fertilizer (10-5-13): Polymer-Coated Slow Release with Sulfur, Magnesium & Calcium Buy on Old Cobblers Farm
Most tomato fertilizers are just NPK in a bag. This one includes polymer-coated urea for extended feeding, plus sulfur, magnesium, and calcium from langbeinite and gypsum — the secondary nutrients that actually determine fruit flavor and quality.
Old Cobblers Farm™ Wicked Growth 10-5-13 Fertilizer – High Potassium Blend
by Conventional Fertilizer — Littleton, NH
Engineered for Fruiting Crops
The 10-5-13 ratio prioritizes potassium for fruit sizing, sweetness, and firmness while providing steady nitrogen for vine growth and moderate phosphorus for root support.
Polymer-Coated Slow Release
Purkote polymer-coated urea releases nitrogen gradually over weeks. No burn risk, fewer applications, and steady feeding through critical fruiting windows.
Sulfur, Magnesium & Calcium Built In
Langbeinite delivers magnesium and sulfur. Gypsum adds calcium. These secondary nutrients prevent blossom end rot, boost chlorophyll, and enhance flavor compounds.
Potassium-Heavy for Sweetness
13% potassium drives sugar accumulation, improves berry size and firmness, and extends shelf life for strawberries, tomatoes, and all fruiting crops.
Versatile Coverage
Garden rate covers 170–250 sq ft per 5 lb bag. Lawn rate stretches to 1,000 sq ft. Reapply 2–3 times per season.
6-Ingredient Professional Blend
Not a simple 3-component mix. Six precision ingredients deliver primary, secondary, and slow-release nutrition in a single application.
Works for All Fruiting Vegetables
Tomatoes, strawberries, peppers, eggplant, cucumbers, melons, squash — any crop that sets fruit benefits from this K-heavy, calcium-enriched formula.
Trusted by 20,000+ Growers
Developed in Littleton, New Hampshire. Sold nationwide on Amazon, Walmart, eBay, and theoldcobblersfarm.com.
| NPK Ratio | 10-5-13 |
| Item Form | Slow-release granular (polymer coated) |
| Coverage | 170–250 sq ft (garden) | 1,000 sq ft (lawn) per 5 lb bag |
| Category | Conventional Fertilizer |
| Type | All-Purpose NPK Blends |
| Sizes | 5 lb | 10 lb | 15 lb | 20 lb |
| NPK | 10-5-13 |
| Nitrogen | 10% (polymer coated) |
| Phosphorus | 5% available phosphate |
| Potassium | 13% soluble potash |
| Secondary | Sulfur, Magnesium, Calcium |
| Form | Slow-release granular |
| Rate | 2–3 lbs / 100 sq ft |
| Method | Broadcast, side-dress, or band |
| Sizes | 5, 10, 15, 20 lb bags |
| Best For | Tomatoes, strawberries, peppers, fruiting crops |
| Feature | Old Cobblers Farm™ Wicked Growth 10-5-13 Fertilizer – High Potassium Blend Old Cobblers Farm | Shake 'N Feed Tomato, Fruit & Vegetable Miracle-Gro | Shake 'N Feed All Purpose Miracle-Gro | Smart-Release Plant Food Plus Osmocote | Acid Mix Down to Earth | Fruit Tree Fertilizer Down to Earth | Berry-Tone Organic Espoma | CitrusGain BGI |
|---|---|---|---|---|---|---|---|---|
| NPK | 10-5-13 | 10-5-15 | 12-4-8 | 15-9-12 | 4-3-6 | 6-2-4 | 4-3-4 | 8-3-9 |
| Form | Slow-release granular (polymer coated) | — | — | — | — | — | — | — |
| Coverage | 170–250 sq ft (garden) | 1,000 sq ft (lawn) per 5 lb bag | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed |
| Price / Size | 5 lb | 10 lb | 15 lb | 20 lb | $12–$17 | $12–$25 | $8–$30 | $6–$30+ | $12–$105 | $12–$13 | $10–$30 |
| Our Take | The most complete fruiting-crop fertilizer in the Wicked Growth lin... | — | — | — | — | — | — | — |
Shake 'N Feed Tomato, Fruit & Vegetable
Shake 'N Feed All Purpose
Smart-Release Plant Food Plus
Acid Mix
Fruit Tree Fertilizer
Berry-Tone Organic
CitrusGain
Engineered for Fruiting Crops
The 10-5-13 ratio prioritizes potassium for fruit sizing, sweetness, and firmness while providing steady nitrogen for vine growth and moderate phosphorus for root support.
Polymer-Coated Slow Release
Purkote polymer-coated urea releases nitrogen gradually over weeks. No burn risk, fewer applications, and steady feeding through critical fruiting windows.
Sulfur, Magnesium & Calcium Built In
Langbeinite delivers magnesium and sulfur. Gypsum adds calcium. These secondary nutrients prevent blossom end rot, boost chlorophyll, and enhance flavor compounds.
Potassium-Heavy for Sweetness
13% potassium drives sugar accumulation, improves berry size and firmness, and extends shelf life for strawberries, tomatoes, and all fruiting crops.
