From our perspective as Calibrachoa plants, the most critical aspect of fertilization is consistency. Our entire purpose is to produce a spectacular, uninterrupted display of trumpet-shaped blooms from spring until the first frost. This is an energetically expensive endeavor. To support this non-stop floral show, we require a steady stream of specific nutrients, primarily phosphorus (the middle number on fertilizer packages) for bud formation and potassium for overall plant vigor and flower quality. A feast-or-famine approach is highly disruptive. A sudden surge of fertilizer can burn our delicate feeder roots, while a period of starvation forces us to halt flower production to conserve energy for basic survival. A gentle, continuous supply is what allows us to focus our energy on what you appreciate most: blooming profusely.
While we need a full spectrum of macro and micronutrients, the formula of the fertilizer you choose sends us a direct signal. A fertilizer with a high first number (Nitrogen) tells our system to prioritize green, leafy growth. This results in lush foliage at the expense of flowers. What we truly crave is a blend that encourages blooming. A fertilizer with a ratio like 15-7-15, 12-15-12, or a similar formulation where the phosphorus (P) and potassium (K) values are prominent is ideal. These formulations provide the perfect building blocks for creating strong stems, developing vibrant flower pigments, and sustaining the metabolic processes behind continuous blooming. Many fertilizers labeled specifically for "bloom boosters" or "flowering plants" are formulated this way.
The method of delivery is just as important as the formula itself. For us Calibrachoa, especially those of us living in containers or hanging baskets with limited soil volume, liquid fertilizers are superior. When you mix a water-soluble fertilizer into your watering can, it immediately becomes available to our root system. We can uptake these nutrients directly and efficiently, translating them into new flower buds within days. Slow-release granules are a helpful foundation, providing a baseline of nutrition, but they cannot always keep up with our rapid growth and heavy blooming demands, particularly as temperatures fluctuate or after heavy rainfall that can leach nutrients away. A weekly liquid feeding regimen, using a half-strength dose, is like providing us with a constant, easily digestible meal that perfectly fuels our flowering cycle.
Our needs are not static; they change with the environment. During periods of intense heat or heavy, frequent rain, our soil can become depleted of nutrients more quickly. Similarly, if you notice our lower leaves turning pale green or yellow, it is a clear sign of nitrogen deficiency—we are cannibalizing our older leaves to support new growth. If our flowering slows down significantly, it often indicates a lack of phosphorus. Please view these not as failures but as communication. They are our way of asking for a slight adjustment in your feeding schedule. In stressful conditions, you might need to supplement more frequently. Observing our condition allows you to fine-tune the fertilization practice to perfectly match our physiological demands.
