Best Annual Flower Fertilizer (15-30-15): Maximum Phosphorus Bloom Booster for Non-Stop Color All Season Buy on Old Cobblers Farm
Annual flowers exist to bloom — and they need massive phosphorus to do it. This 15-30-15 delivers 30% P₂O₅, the highest in the Wicked Growth lineup, pushing maximum flower bud formation, intense petal color, and continuous bloom production from planting to frost.
Old Cobblers Farm™ Wicked Growth Annual Flowers Fertilizer
by Conventional Fertilizer — Littleton, NH
30% Phosphorus — Maximum Bloom Power
Double the phosphorus of any balanced formula and triple the P of most garden fertilizers. Phosphorus drives flower bud initiation, petal count, and continuous rebloom.
Vivid, Saturated Color
Phosphorus fuels the biochemical pathways that produce intense flower pigmentation — deeper reds, brighter yellows, richer purples, and more vivid pinks.
15% N + 15% K Support
Balanced nitrogen maintains healthy green foliage without pushing leggy growth, while potassium strengthens stems and improves heat and drought tolerance.
480 Pots Per Bag
At 1 tsp per 6" pot, one 5 lb bag feeds approximately 480 individual containers per application. For beds, covers ~160 sq ft.
Every 3–4 Weeks
Annuals are heavy feeders that deplete nutrients quickly. Reapply every 3–4 weeks through bloom season for uninterrupted flower production.
Dissolves for Liquid Feeding
Can be dissolved in water for container drenching and hanging basket feeding. Versatile application for beds and pots alike.
All Annual Varieties
Petunias, marigolds, zinnias, impatiens, begonias, snapdragons, cosmos, dahlias, geraniums — every annual flower benefits from high-P feeding.
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Developed in Littleton, New Hampshire. Sold nationwide on Amazon, Walmart, eBay, and theoldcobblersfarm.com.
| NPK Ratio | 15-30-15 |
| Item Form | Granular |
| Coverage | ~160 sq ft beds | ~480 pots per 5 lb bag |
| Category | Conventional Fertilizer |
| Type | Flower & Garden |
| Sizes | 5 lb | 10 lb | 15 lb | 20 lb |
| NPK | 15-30-15 |
| Nitrogen | 15% |
| Phosphorus | 30% available phosphate |
| Potassium | 15% soluble potash |
| Form | Granular |
| Rate | 1 tbsp / sq ft (beds) or 1 tsp / 6" pot |
| Method | Broadcast, incorporate, or dissolve |
| Frequency | Every 3–4 weeks |
| Sizes | 5, 10, 15, 20 lb bags |
| Best For | Petunias, marigolds, zinnias, all annuals — beds, pots, hanging baskets |
| Feature | Old Cobblers Farm™ Wicked Growth Annual Flowers Fertilizer Old Cobblers Farm | Bloom Booster Flower Food Miracle-Gro | Blossom Booster Jack's | Smart-Release Flower/Veg Osmocote | Ultra Green All Purpose Pennington | Super Bloom Scotts | Bloom Booster Grow More | Flower Plant Food Expert Gardener | All Purpose Food True Organic | Flower & Rose Granular Jobe's Organics | Big Bloom FoxFarm |
|---|---|---|---|---|---|---|---|---|---|---|---|
| NPK | 15-30-15 | 10-52-10 | 10-30-20 | 14-14-14 | 10-10-10 | 12-55-6 | 10-52-10 | 10-10-10 | 4-4-4 | 3-5-4 | 0-0.5-0.7 |
| Form | Granular | — | — | — | — | — | — | — | — | — | — |
| Coverage | ~160 sq ft beds | ~480 pots per 5 lb bag | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed | Not listed |
| Price / Size | 5 lb | 10 lb | 15 lb | 20 lb | $10.49 | $16.99 | $22.97 | $20.95 | $14.00 | $16.89 | $5.97 | $21.24 | $12.99 | $19.99 |
| Our Take | The highest-phosphorus formula in the entire Wicked Growth catalog.... | — | — | — | — | — | — | — | — | — | — |
Bloom Booster Flower Food
Blossom Booster
Smart-Release Flower/Veg
Ultra Green All Purpose
Super Bloom
Bloom Booster
Flower Plant Food
All Purpose Food
Flower & Rose Granular
Big Bloom
30% Phosphorus — Maximum Bloom Power
Double the phosphorus of any balanced formula and triple the P of most garden fertilizers. Phosphorus drives flower bud initiation, petal count, and continuous rebloom.
Vivid, Saturated Color
Phosphorus fuels the biochemical pathways that produce intense flower pigmentation — deeper reds, brighter yellows, richer purples, and more vivid pinks.
15% N + 15% K Support
Balanced nitrogen maintains healthy green foliage without pushing leggy growth, while potassium strengthens stems and improves heat and drought tolerance.
480 Pots Per Bag
At 1 tsp per 6" pot, one 5 lb bag feeds approximately 480 individual containers per application. For beds, covers ~160 sq ft.
