Hello, it is I, your Calibrachoa. I am usually a fountain of vibrant, cheerful blooms, but when my leaves start to turn yellow, I am trying to tell you that my needs are not being met. It is my language, and I need you to listen. Let me explain the reasons from my perspective.
Perhaps you are being too generous with the watering can. My roots are not like those of a water lily; they need to breathe. When I am sitting in constantly soggy, waterlogged soil, my roots begin to suffocate and rot. This root rot means I can no longer absorb the water and nutrients I desperately need, so my lower leaves will turn yellow and wilt as a distress signal. Please, check the soil before watering. Stick your finger an inch deep—if it feels moist, wait. I need the soil to dry out slightly between drinks.
I am a heavy feeder. To produce my massive show of flowers, I require a steady supply of energy, particularly nitrogen, iron, and magnesium. Nitrogen keeps my foliage green and vigorous. When I am running low, my older leaves will often turn a pale, uniform yellow as the plant moves these essential nutrients to support new growth. A lack of iron (chlorosis) shows as yellowing between the veins of my newest leaves. Please, feed me. A balanced, water-soluble fertilizer applied every week or two, or a slow-release fertilizer mixed into my soil at planting, will keep me well-nourished and green.
If I have been growing in the same container for a long time, my roots may have exhausted the available space and nutrients in the soil. When I become pot-bound, my roots form a tight, tangled mass that cannot effectively take up water or fertilizer, no matter how much you provide. This stress directly leads to yellowing leaves and a general decline in my health. If you notice my roots circling the inside of the pot or growing out of the drainage holes, it is time for an upgrade. Gently transplant me into a slightly larger home with fresh, nutrient-rich potting mix.
Sometimes, my yellowing leaves are a sign of unseen attackers. Sap-sucking pests like spider mites or aphids can infest my stems and the undersides of my leaves, draining my vitality and causing stippling and yellowing. Fungal diseases, often encouraged by wet foliage and poor air circulation, can also be the culprit. Please, inspect me regularly. Look for tiny bugs, fine webbing, or spots on the leaves. A strong spray of water, insecticidal soap, or neem oil can help evict the pests. For fungal issues, improve air flow around me and avoid wetting my leaves when you water.
