Have you ever delved into a bag of compost and noticed small white objects in the mix? Quite often these balls are recycled polystyrene but most likely they are a beneficial mineral product called Perlite and seasoned gardeners use it extensively.
In nature, Perlite exists as a type of volcanic glass, created when the glass is saturated with water over a long period of time. The Perlite we see today could be described as “Volcanic Popcorn”, and is created after the glass is crushed, then baked at very high temperatures. The heat softens the mineral structure, allowing the water trapped inside to expand, thereby increasing the size of the particles by up to 16 times their original mass.
Perlite granules have a lot of porous openings inside them and are clean, sterile and physically stable. They do not contain any toxic chemicals, have a neutral pH and retain their shape when pressed into the compost, thereby facilitating the two critical properties required in any quality growing media, aeration and drainage.
Aerating the soil allows small pockets of air to remain in the soil, assisting the growth of strong root systems. When the soil gets packed down, the air pockets are lost, but since Perlite is a harder mineral, it retains its shape keeping those air pockets around the roots.
Proper drainage is crucial to prevent the root system being starved of oxygen, causing eventual death. Perlite retains water on its large pitted surface area allowing excess water to drain away.
Perlite is great for use in compost mixes and propagation. It is widely used in the ever-growing industry of hydroponics and soil-less horticulture and as an additive to compost for indoor plants, patio plants and established pot grown shrubs and trees.
Perlite is a safe organic additive and helps lower the environmental impact in sustainable gardening. We recommended adding Perlite so it makes up around 10-20% of the total volume of compost mix relative to the amount of water retention you require.