Photo source: The Washington Post
When researching on Strelitzia seed germination, I read that it was recommended to mix the potting soil with perlite. What is perlite, I thought. And is that the same as vermiculite? Vermiculite and perlite are both non-organic soil additives that are used to aerate the soil, but are used for very different reasons.
Vermiculite is made from compressed dry flakes of a silicate material, which makes it absorptive and spongy. The color is golden brown to dark brown and can be hard to spot if its mixed in potting soil. Vermiculite interacts with among other calcium and magnesium in the soil, and also helps to rais the pH slightly. When you add water to vermiculite, the flakes expand and act like an absorbing sponge. It can absorb 3 to 4 times its volume! Vermiculite will hold water in the soil until the soil begins to dry out and releases it. Therefor vermiculite is very useful for plants that love water and require soil to stay damp and not dry out. Anyhow, because vermiculite acts like a sponge, it doesn’t aerate the soil as well, which means less oxygen for plant roots. Be very aware of which of your plants like moist soil or you might find your plants suffering from root rot.
Perlite is made of volcanic glass and is formed when obsidian contacts water, creating a unique type of volcanic glass with a high water content. When applied heat (1.200 celcius degrees) to perlite, it puffs up 20 times its size into little white balls. It retains some water but most important air on the surface in hidden nooks and crannies. Therefor perlite is perfect for soil aeration, lightening the soil and giving better drainage and oxygen access for your plant’s roots. If you are growing plants, that require soil to dry out completely between watering like cacti or succulents, perlite is a great addition to the potting soil.