Miracle-Gro 2756310 Plant Food, 3.3 lb Pail, Powder, 15-30 ...Miracle-Gro Water Soluble Ultra Bloom Plant Food (15-30-15) 1.5 kg is a high-phosphorus, fast-acting fertilizer designed to boost blooms and vibrant colors in annuals, perennials, and containers. It is applied every 7–14 days for optimal results.