Calcium is used to fortify plant cell walls, much like it fortifies our bones and teeth. When we use ground or tap water, often rich in calcium and other minerals, it has a tendency to precipitate out and become a solid. As water evaporates, the calcium is left behind, forming a white, chalky residue. You may have seen calcium buildup or deposits in your bathroom, in the shower, even the kitchen sink. In plants, you’ll find it on leaves that got wet or on porous ceramic pots like terracotta. On ceramics, there’s no harm in leaving it, especially if the rustic look is your thing. On leaves though, while harmless, can look ugly and possibly clog pores when it builds up.
Science & Solutions
Calcium is an “alkali-earth” metal with low density, resistant to heating and dissolving, and never occurs pure in nature. “Alkali” because it forms alkaline solutions with water and other elements. The term “earth” refers to non-metallic substances, like rocks and chalk. This is not entirely accurate, as we now know that we can in fact extract calcium in its purest form from the “earth”, which is a metal that reacts with air and substances around it.
Because calcium has a low solubility in water, it is so easily left behind when water dries up. Its alkali nature means it can react with acids to become soluble. If you want to rid your plants or pots of calcium buildup, use a simple acid like lemon juice or vinegar to dissolve the calcium salts. We recommend mixing 1 parts lemon juice to 3 parts water (a 25% solution) OR 1 parts vinegar to 4 parts water (a 20% solution). Wipe the leaves with a rag soaked in this solution and the calcium should come right off. Repeat until it has all been removed.