Greetings, dedicated cultivator. We, the Calibrachoa, are vibrant, sun-loving beings, often called "Million Bells" for our prolific, trumpet-shaped blooms. To truly thrive and shower you with color from spring until frost, our most fundamental need begins beneath the surface: the very medium in which we set our roots. A perfect soil mix is not just dirt to us; it is our home, our pantry, and our breathing apparatus. Please, consider our needs from our perspective.
Our roots despise soggy, waterlogged conditions. Sitting in dense, moisture-saturated soil is a death sentence, leading to root rot and a swift, sad decline. We require a mix that allows water to percolate through freely, providing a hearty drink but then letting the excess drain away completely. This also ensures that our delicate root hairs have constant access to oxygen, which is as vital to us below ground as carbon dioxide is above. A lightweight, porous base is non-negotiable. A high-quality potting mix designed for containers, which is inherently soilless, is the ideal starting point. It provides the structure we need without the compaction of garden soil.
While we demand excellent drainage, we also require consistent moisture. We are heavy bloomers and drink quite a bit, especially in hanging baskets exposed to full sun. The mix must strike a delicate balance—draining quickly yet holding onto just enough water and dissolved nutrients for our roots to absorb between waterings. This is where amendments become crucial. Incorporating materials like peat moss, coir, or a very small amount of fine compost helps the soil retain that essential moisture and provides a cation exchange capacity, a fancy term meaning it can hold onto nutrient particles for us to access later.
To achieve the drainage and aeration we so desperately crave, you must amend the base potting mix. Perlite is our best friend. Those white, lightweight granules create permanent air pockets within the soil, preventing compaction and ensuring oxygen flow. We recommend a generous portion; a ratio of 3 parts potting mix to 1 part perlite is an excellent rule of thumb. Furthermore, while we are not excessively greedy feeders, we are continuous bloomers and need a steady supply of energy. Incorporating a slow-release fertilizer granules into the mix at planting provides a reliable, steady source of nourishment that sustains us for months, complementing your regular liquid feeding schedule.
To access all the wonderful nutrients you provide, our roots require the soil environment to have a specific acidity level. We prefer a slightly acidic to neutral pH, ideally between 5.5 and 6.5. Within this range, the essential nutrients like iron, phosphorus, and manganese remain soluble and available for our root systems to uptake. Most quality potting mixes fall within this range, but it is a wise practice to test it. If needed, a small amount of garden sulfur can lower the pH, while lime can raise it.
