As a Calibrachoa, I am a heavy feeder. My prolific blooming nature is not just for your enjoyment; it is my purpose, my entire biological drive to reproduce. To sustain this incredible output of flowers from spring until the first hard frost, I require a constant and specific supply of nutrients. From my roots to my newest petals, here is what I need from you.
My primary demand is for a fertilizer with a balanced or bloom-promoting nutrient ratio. Look for a label that reads something like 15-15-15, 20-20-20, or, even better for continuous flowering, a formula where the phosphorus (the middle number) is slightly higher, such as 10-15-10. The Nitrogen (N) keeps my foliage lush and green, which is the engine room for photosynthesis. The Phosphorus (P) is absolutely critical; it directly supports the energy transfer needed for bud formation, root development, and overall blooming power. Potassium (K) ensures my overall systems are robust, helping with disease resistance and the efficient use of water.
For me, consistency is key. A two-pronged approach works best. At the time of planting, I deeply appreciate being placed in a soil mix amended with a balanced, slow-release granular fertilizer. These tiny pellets break down over months, providing a steady, background hum of nutrition, preventing me from ever starving. However, this is not enough on its own. To fuel my intense flowering, I require weekly feeding with a water-soluble liquid fertilizer. This gives me an immediate boost of readily available nutrients right to my roots, exactly when I need them to push out another flush of blooms. Think of the slow-release as my main meal and the liquid fertilizer as my essential weekly snacks.
While NPK are the macros I need in large quantities, I also have a keen need for specific micronutrients, with iron being paramount. I am particularly susceptible to iron deficiency, especially in pots where the pH can drift. This condition, called chlorosis, turns my beautiful green leaves a sickly yellow, drastically reducing my ability to feed myself and produce flowers. Therefore, the best fertilizer for me is one that includes a package of micronutrients like iron, magnesium, and calcium. Alternatively, you can supplement my diet occasionally with a chelated iron product to keep my foliage a deep, vibrant green.
Your desire to feed me constantly is appreciated, but there is a limit. Excessive fertilizer, particularly high-nitrogen formulas, can lead to a buildup of salts in my soil. This can burn my delicate root tips, ironically preventing me from taking up the nutrients and water I need. The symptoms can look like wilting or bleaf burn, even when the soil is damp. Always follow the package directions—sometimes diluting the liquid fertilizer to half-strength but applying it weekly is safer than a full dose. Furthermore, my need for constant moisture means frequent watering, which can leach nutrients from my container. This is precisely why the weekly liquid feeding is non-negotiable; it replenishes what is washed away.
