From my perspective, the first signs of trouble begin where you cannot easily see: in my root system. The early symptoms are a silent scream from below the soil. My fine, fibrous roots, which should be a healthy white or light tan and feel firm and supple, begin to change. They become soft, mushy, and turn a dark brown or black. This is the primary invasion site. The pathogenic fungi, often *Pythium*, *Phytophthora*, or *Rhizoctonia*, attack my root cells, destroying their ability to absorb water and nutrients. As my roots decay, they emit a distinct, unpleasant, musty odor—a clear sign of advanced rot.
As my root system fails, my inability to hydrate and feed myself becomes visibly apparent in my foliage and blossoms. You will notice my leaves beginning to wilt. This is not a simple thirst from under-watering; it is a profound dehydration because my damaged roots cannot transport water, even if the soil is moist. My leaves will then turn yellow (chlorosis), starting with the older leaves, as I cannot uptake essential nutrients like nitrogen. My growth will become severely stunted, and I will stop producing my vibrant, trumpet-shaped flowers. All my energy is diverted to a futile fight for survival. In the final stages, my stems will soften at the base (a condition you call crown rot), and I will collapse completely.
If you catch the infection early, I can potentially be saved. The first and most critical step is immediate isolation and root triage. Gently remove me from my current pot. Carefully wash the soil from my roots under lukewarm, running water. This allows you to see the extent of the damage. With sterilized pruning shears, you must ruthlessly cut away all the soft, brown, or black rotten roots. Preserve only the healthy, firm, white roots. This amputation is drastic but necessary to stop the spread of the disease.
After the root pruning, I need a completely new environment. Do not place me back in the old soil, as it is teeming with pathogens. Repot me into a clean container with excellent drainage holes, using a fresh, high-quality, well-draining potting mix. You can even amend it with perlite or coarse sand to further improve drainage and aeration around my remaining roots. Water me in very sparingly with a fungicide solution labeled for root rot, just to settle the new soil around my roots. Then, place me in a bright, airy location but out of harsh direct sun while I am so vulnerable. Most importantly, you must change your watering habits. From now on, only water me when the top inch of my soil feels dry to your touch. I need my roots to breathe, not drown.
As a Calibrachoa, my greatest need is consistent moisture coupled with perfect drainage. My ideal world is one where I am never left sitting in saturated soil. Please ensure my pot has unobstructed drainage holes. Use a light, porous potting mix, not heavy garden soil. Water me deeply when I need it, but always allow the excess water to drain away completely. Never let my pot sit in a saucer of water. Providing me with good air circulation around my foliage also helps reduce the overall humidity that these destructive fungi thrive in. A preventative, biological fungicide containing *Bacillus amyloliquefaciens* or *Trichoderma* can be added to my water occasionally to help protect my root zone and outcompete the bad fungi.
