If you've ever done an online search for the differences between perlite and vermiculite, you've likely ended up with a head full of information, but perhaps more questions than answers. Our goal with this post is to give a quick summary of when to use one vs. the other in a straightforward and practical way.
Without getting into too much detail, let's quickly explain the similarities and differences between them:
Both perlite and vermiculite are inorganic, meaning in the simplest terms, neither was derived from any living thing (It technically means that neither contain carbon atoms, *best narrator voice* the building blocks of life on earth...but now we're getting into science.). It does not mean, however, that if you use perlite or vermiculite in your garden, it will no longer be an organic garden. Confusing a bit, we know, but just think of them as neither helping nor hurting your organic gardening goal. They're just additives used in organic and non-organic gardening.
Both are good solutions for aerating the soil (making sure oxygen gets to the roots of your plants, which helps the plants turn sugars into energy they use to grow...oops science again.), though perlite does a better job on this point. More on that later.
The other point they have in common is that they are both relatively inexpensive. Always nice.
By the way, if you thought that those little white things in soil were polystyrene foam and may be bad for the environment, you're not alone. I spent much of my life thinking this. They aren't in fact, and are actually made by super-heating volcanic glass, causing it to pop like popcorn (also science, but still pretty cool).
Now, some may recommend using either perlite or vermiculite as additive in your soil mix, but there are some important differences:
Perhaps the most important difference is in how they retain water. Your plant roots need water as much as you do. However, too much water could lead to major problems such as root rot or damping off (a fungi problem that can kill plants overnight)!
We could go into a lot of detail about their water retention properties and how they differ, but this info is available in the thousands of articles already written. Instead, let's focus on when to use perlite and when to use vermiculite.
Vermiculite retains more water in the soil for longer. Think of it as a sponge that absorbs water and releases it slowly. This makes vermiculite great for seed germination and for plants that love their feet wet such as: Canna, Bee Balm, Iris, Phlox, Hibiscus, Ferns, Rue. Just remember to check the requirements of your individual plant to see what it likes. If it likes moist or damp soil, then vermiculite could be a great additive.
Perlite also retains water, but releases it quickly and aids in drainage. This makes it a great solution for rooting cuttings, where excess moisture can lead to issues. It's also great for plants that love well drained soil. Honestly, the list of plants that love good drainage is so extensive, it's too long to list here. Just remember to read up a bit on your individual variety to see what kind of soil it likes. If good drainage is required, we recommend using perlite vs. vermiculite.
Lastly, here's a fun fact: In 1824 Thomas Webb discovered that when mica ore was heated over a flame, it stretched out like a worm. He named this new discovery vermiculite after the Latin word, vermiculus meaning worm. The word perlite comes from the French word meaning pearl, as the individual granules resemble tiny pearls. Now you know. Time to impress your friends with your vast scientific and gardening knowledge!