From our perspective, nothing is more critical than the balance of air and water around our roots. We Calibrachoa are heavy bloomers, which demands constant access to water and nutrients, but our roots absolutely despise sitting in soggy, oxygen-deprived soil. A dense, waterlogged mix will suffocate us, leading to root rot and a swift decline. Therefore, the primary request for our potting mix is excellent drainage coupled with a slight ability to hold onto moisture. A base of high-quality peat moss or coir (coconut fiber) provides the necessary moisture retention, while the addition of coarse horticultural perlite ensures that excess water drains away quickly, creating air pockets that allow our root systems to breathe and expand healthily.
To produce the prolific cascade of blooms you humans so enjoy, we require a consistent and accessible source of nutrition. We are not heavy feeders in the sense of needing an overly rich soil, but we are continuous feeders. A initial charge of nutrition is welcome. Incorporating a balanced, slow-release fertilizer granules into the mix at planting provides a steady, gentle supply of essential nutrients like nitrogen for foliage growth, and phosphorus for root and flower development over several months. This acts as our foundational meal, preventing the stress of nutrient deficiency between your regular liquid feedings, which we will also greatly appreciate.
You may not consider it, but the acidity or alkalinity of our soil environment is paramount to our health. We Calibrachoa prefer a slightly acidic to neutral pH, ideally between 5.5 and 6.5. In this range, the vital micronutrients we need—particularly iron—are readily available for our roots to absorb. If the pH is too high (alkaline), these nutrients become locked up in the soil, unavailable to us. This leads to chlorosis, where our leaves turn a sickly yellow while the veins remain green, drastically reducing our vigor and ability to photosynthesize. Including a small amount of dolomitic lime can help buffer the natural acidity of peat moss and stabilize the pH within our desired happy range.
Combining these elements into a mix creates the perfect growing medium for us to thrive. A simple and effective recipe you can make is: two parts peat moss or coir for moisture control, one part perlite for impeccable drainage and aeration, and one part quality compost or worm castings for a boost of organic matter and beneficial microbes. To this, mix in a balanced slow-release fertilizer according to the product's label rates, and a handful of dolomitic lime to adjust the pH. This blend provides the physical structure, moisture management, and nutritional foundation we need to establish a strong root system and support months of vibrant flowering.
