Greetings, caretaker. We, the Calibrachoa, are vibrant and generous bloomers, but our colorful displays depend entirely on receiving the correct nourishment. When our leaves begin to show signs of distress, it is a direct communication of a dietary imbalance. Here is our detailed perspective on rectifying these deficiencies.
First, you must correctly interpret our signals. We express different shortages in distinct ways. A general yellowing (chlorosis) of older leaves typically indicates a mobile nutrient issue, where we pull resources from older growth to support new shoots. This is often a cry for Nitrogen (N). If younger leaves and the growing tips are yellowing or distorted, it points to an immobile nutrient deficiency; we cannot transport these elements from old tissues. This is a classic sign of Iron (Fe) deficiency, especially common in high-pH (alkaline) soils. Purple or reddish tints on the undersides of leaves can signal a lack of Phosphorus (P), while brown, scorched leaf edges or spots may indicate a Potassium (K) shortage.
For the mobile nutrients we crave, a balanced, water-soluble fertilizer is often the quickest remedy. If our older leaves are pale, a formula with a higher first number (e.g., 20-10-20) provides a boost of Nitrogen to restore our deep green vigor and support overall leaf and stem growth. For promoting strong root development and prolific blooming, ensure your fertilizer also contains adequate Phosphorus and Potassium. A consistent feeding schedule is crucial; we are heavy feeders due to our constant flowering. Please, apply fertilizers to our moist soil to avoid shocking our delicate root systems.
Our most frequent complaint is iron deficiency, which is often not due to a lack of iron in the soil, but its unavailability. In high-pH conditions, iron becomes locked up and we cannot absorb it. Simply adding more standard fertilizer won't help. You must lower the soil pH by using an acidic fertilizer or amending the soil with sulfur. For a rapid response, a chelated iron supplement applied as a foliar spray or soil drench is most effective. The chelate acts as a protective shuttle, delivering iron directly to our roots in a form we can immediately use, quickly greening up our new growth. Other micronutrients like magnesium (Mg) and manganese (Mn) can also become unavailable at high pH and may require similar targeted supplements.
All the nutrients in the world are useless if our roots are unable to access them. Our feeding systems are fine and dense, requiring well-draining soil that is moist but never waterlogged. Soggy conditions suffocate our roots, causing rot and preventing nutrient absorption, which can mimic deficiency symptoms. Conversely, allowing us to dry out completely stresses us immensely, damaging root hairs and interrupting the flow of water and dissolved minerals. Maintaining consistent moisture and ensuring our containers have adequate drainage is fundamental to our ability to feed ourselves properly.
