Perlite and Pumice in Potting Soil
By: Black Gold
Have you ever wondered what those little white things in your potting soil are? In most instances they are perlite and/or pumice. Perlite is a mined siliceous rock that is heated and expanded, or “popped” like popcorn, into a white lightweight material, while pumice is a soft, insert-mined stone that often comes from Oregon. What makes Black Gold® Perlite and Black Gold® Pumice particularly desirable is that both are screened for uniformity, with the finer particles removed.
Both perlite and pumice are porous aggregates, meaning they are added to a potting soil to improve aeration and drainage. The addition of perlite and pumice in a potting soil will also increase the moisture and nutrient retention of the potting soil. Just like peat moss, they act like reservoirs in retaining water and nutrients and release them when they are needed by the plant.
Due to its weight, pumice provides bulk density to a potting soil. This trait is valuable when you are growing outdoor containers and you don’t want them to blow over in the wind. Pumice is often the aggregate choice for specialty potting soils (cactus, bonsai) because it provides great aeration and helps anchor roots.
In addition to being a potting soil mix component, perlite is an excellent neutral medium for starting seeds and rooting cuttings. It can also be used to store bulbs and as an essential hypertufa planter ingredient.