Perlite vs Vermiculite: What’s the Difference?

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If you’re like me, you’ve probably been in this position before…

You’re standing in the garden center trying to decide between perlite and vermiculite. All you can remember is that one looks like little Styrofoam balls.

The difference between perlite vs vermiculite is important to know for the prosperity of your garden. They seem very similar, but differ in a few crucial ways.

Let’s get into the details and clear up any confusion you have!

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What is Perlite?

Hydroponic Growing Media Perlite
Perlite

Perlite is lightweight, easy to handle, clean and has no odor. It has a pH of 6.6 to 7.5.

The life of a bag of perlite begins as volcanic glass — but not any type of volcanic glass. It’s formed when obsidian contacts water, creating a unique type of volcanic glass with a high water content. When manufacturers apply heat to perlite, it puffs up into little white balls. Often times they’ll mix these little white balls — what we call perlite — into potting soils to aid with soil aeration and water retention. It retains some water but also air on the surface of the little balls in all the hidden nooks and crannies.

Perlite is a good choice when you have plants in your garden that require soil to dry out completely between watering. For example, if you’re growing a cactus or a succulent, perlite is a great addition to the soil.

Because it’s so porous, perlite does allow excess water to drain quickly…sometimes all over your porch. It has a tendency to easily crush into a powder between your fingers, but this usually isn’t a problem because it doesn’t encounter that type of pressure in your pots or beds. It’s chief use is to improve soil aeration, lightening the soil and giving better drainage and oxygen access for your plants’ roots.

What is Vermiculite?

Hydroponic Media - Vermiculite
Vermiculite

Vermiculite interacts with potassium, calcium and magnesium in your soil. It also helps to raise the pH slightly of your plants even though it’s a neutral pH of 7.0.

Vermiculite is made from compressed dry flakes of a silicate material which is absorptive and spongy. The color of vermiculite is a golden brown to a dark brown and is a sometimes difficult to tell from the potting soil it’s mixed with. When water is added to vermiculite, the flakes expand into a worm-like shape and act like an absorbing sponge. If you want to poke these “vermiculite worms” with your fingers, you’re not alone — that’s what I wanted to do when I first saw them too!

Vermiculite is best used for plants that require soil to stay damp and not dry out. For plants that love water, using vermiculite or mixing a healthy scoop of it into your potting soil is the way to go. It can absorb 3 to 4 times its volume when water is added, making your pots a little bit on the heavy side.

Since vermiculite acts like a sponge and absorbs more water than perlite, it doesn’t aerate the soil as well. This means less oxygen for plant roots. If you use it when growing plants that don’t need damp soil, you might find your plants suffering from root rot. So be aware of your plants’ needs when you decide how water retentive you want your soil to be.

More Differences Between Vermiculite and Perlite

There are major differences between vermiculite and perlite, making it important to choose the right one, lest your garden be ruined by a bad growing media choice.

We’ve already covered the biggest difference: Vermiculite will mix with soil and help to retain water. Perlite, on the other hand, will add drainage to the soil that it’s mixed with.

Vermiculite finds its way into many seed starting systems. It both protects seedlings from fungus that so often ruins seed starting, and helps to retain water in the tiny little pods that seeds start in. While perlite can be used with seedlings, it’s better used when you move your seedlings into separate pots for additional drainage.

Which To Use In Your Garden?

There’s a large discussion in the gardening community on which to use in the garden. Here’s the truth: it’s a false debate. They both have their own purposes in the garden.

Use Perlite If…

  1. You have plants that need to dry out before watering again
  2. When you move your seedlings to separate pots
  3. You need to loosen clay soil in your garden

Perlite when added to clay soils, it can eliminate both surface crusting and puddles. It will also help to reduce fluctuations in soil temperatures in your garden soil. Perlite will also improve both drainage and aeration in your home gardens. Horticultural perlite can be bought in different grades according to how you’re going to use it. For general application, a fine to medium grade can be used. It’s free of weeds, disease free and sterile.

Use Vermiculite If…

  1. You need an additive for plants that need to be kept moist
  2. You want your seed trays to develop strong seedlings

Vermiculite is odorless, can be purchased in horticultural-grade bags with directions on working it into the garden soil. It’s a permanent soil conditioner and won’t break down in your soil like compost does. When it is watered or it rains, the vermiculite will hold water in the soil until the soil begins to dry out and releases it. Vermiculite can be used in potted containers, on lawns and for composting. It can be used in mycology for mushrooms added to the substrate.  It can improve the soil that needs an additive to retain water for your plants which need it.

In summary: Both are good additives to your gardening needs, you just need to know what you’re using them for!


The Green Thumbs Behind This Article:


Kevin Espiritu
Founder

The difference between vermiculite vs. perlite can be a little confusing and has caused debate amongst gardeners. Find out which to use in your garden.
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28 thoughts on “Perlite vs Vermiculite: What’s the Difference?”

  1. Hi Kevin
    I am trying to germinate Clivia seeds. Is it better to use vermiculite rather than perlite.
    After germination the seeds will be transferred into a special Clivia mix for the term of being a seedling which could be a couple of years.
    So, a decision, V or P to germinate. What do you suggest Kevin.
    Kind regards
    Gary

    • There’s almost as many ways to germinate clivia as there are people who are trying to do it!

      Methods I’ve seen recommended include:

      – pressing the seed into moistened sand, with about 50% of the seed still exposed
      – using moistened compost or peat moss, again with 50% of the seed still exposed
      – putting a thin layer of moistened vermiculite in the bottom of a plastic container and laying the seeds on top of it
      – using moistened orchid potting mix for both germination and planting purposes

      There’s more, but basically the gist is that you want something that retains moisture but doesn’t pool, and you want to place it somewhere warm enough to spur the germination. Once the seeds have sprouted, you can easily transplant them.

      The problem with perlite in this situation is what while it does have tiny pockets inside the granules which hold water, it isn’t consistently moist. I’d say that if you absolutely have to use either perlite or vermiculite, you should opt for vermiculite… but don’t feel tied to only those two options, because others will work too.

  2. I have lousy clay soil so I’m going to do a raised bed for veggies. Since I live in a high desert location I’m thinking I should mix perlite into the existing soil to loosen it up, but use vermiculite in the raised bed to retain water. What do you think – good solution or unnecessary?

    • I’ve got nasty clay soil as well, so I sympathize! What I personally like to do is blend the existing clay with compost thoroughly to keep the clay particles separated and prevent them from clumping back together. You can add some perlite if you’d like, which will help keep it aerated and well-draining, but the better option is to space out those sticky clay bits with other material. This improves your soil overall.

      Some people also mix sand with their clay, but I tend to avoid doing that whenever possible. I’ve discovered that my particular clay soil will just turn into concrete with the addition of sand. Not a good choice for me!

      Adding vermiculite in a limited quantity can help your soil retain some moisture, but don’t go too heavy with it. It’s much easier to add a little more if you decide it’s necessary than it is to try to add more compost/soil to reduce the amount of vermiculite in the space.

  3. What if I mix both Vermi and Perli togetyher for palm seed germination? Or if mix both into a potting soil for potted trees? What would happen?

    • I do that often actually. What you’re doing is balancing out some of the strengths of one with the strengths of the other. It’s a pretty good idea!

  4. I have raised garden beds that can drain, so I’m glad that I used vermiculite to keep the soil from drying out terribly in our hot summers.

  5. My understanding is that vermiculite may contain trace amounts of asbestos, since these minerals are often found together. Please do your own research on this matter, and make an informed decision.

    • The issue of asbestos in vermiculite was related to a single mine. Once the issue was identified, that vermiculite was not used for horticultural vermiculite. Bags of horticultural vermiculite will usually state that it is asbestos free.

  6. I read about five websites about the differences between perlite and vermiculite. Yours was the clearest and best. Now I know it’s vermiculite I need, not perlite, in my garden soil that has too-good drainage. I will probably also add a little peat moss, just to make the vegies really expensive.

  7. I live in Tucson, Arizona. Our soil requires a lot work to produce a decent garden with a 6 to 6.5 ph. Which to use? Perlite or vermiculite or a combination. Thanks!

    • It all depends on if you need water retention or aeration more, Mack! I’d do a soil test and see. Most people need perlite over vermiculite in general though.

  8. Great article for me. My east texas clay mixed with 5 truckloads of rabbit manure does well until hot weather then ,can’t get enough water on it. Will try vermiculite. Any idea how much on a 10′ x 60′ garden spot?

    • Hard for me to say exactly how much you need. What I’d do is do a 4 x 4′ section and see how much you use to get the consistency and soil texture that you want, and then do some quick math to multiply it out!

  9. Thanks Kevin,
    I tried them both and I think the perlite taste better with 2% milk.
    Eating the vermiculite with whole milk made me a little gassy. But both bowls were pretty good. Any idea if Wal-Mart will stock it on their shelves for the holidays.

  10. Thanks Kevin for all the info. I will use vermiculite in seedling trays to germinate cycad seeds and Perilte in a cycad mixture when i plant them in plastic bags.
    Hope this works.

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