WEBVTT - What's the White Stuff in Soil Mixes?

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<v Speaker 1>Welcome to Brainstuff, production of I Heart Radio. Hey brain Stuff,

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<v Speaker 1>Lauren Bogle Bomb here. Tear open a bag of commercial

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<v Speaker 1>podding soil, and you immediately see a mixture of rich

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<v Speaker 1>black soil and white flex. That white stuff isn't there

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<v Speaker 1>by accident. It's probably pearlite, and it's an essential addition

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<v Speaker 1>that makes the soil more suitable for plant growth. Pearlite

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<v Speaker 1>promotes soil drainage so plant roots don't become water logged.

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<v Speaker 1>We spoke by email with John Tronfeld, director of the

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<v Speaker 1>University of Maryland Extension Home and Garden Information Center. He

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<v Speaker 1>explained it increases poor space in growing media, which is

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<v Speaker 1>critical for aeration, perforating the soil with pockets of air,

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<v Speaker 1>water drainage, and root growth. It doesn't change the peach

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<v Speaker 1>of growing media. Plus, it's sterile and lightweight, making it

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<v Speaker 1>easier to handle and cheaper to ship. But just in

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<v Speaker 1>case you, like me, had no idea what perlite is,

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<v Speaker 1>or where it comes from, or why it's called popcorn

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<v Speaker 1>for your soil, come along. Pearlite is a form of

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<v Speaker 1>amorphous volcanic glass that contains roughly two to five percent water.

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<v Speaker 1>It's a lot like pumice, but denser. Both types of

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<v Speaker 1>glass are formed as molten lava slowly cools. Composition varies

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<v Speaker 1>a bit, but pearlite is made of up to seventy

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<v Speaker 1>silicon dioxide and ten to fift aluminum oxide, plus smaller

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<v Speaker 1>amounts of sodium oxide, potassium oxide, and other minerals. Miners

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<v Speaker 1>extract perlite from the earth using explosives and or machinery.

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<v Speaker 1>There are large mines in countries like Armenia, China, Greece, Japan, Turkey,

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<v Speaker 1>and the United States. Although we here in the US

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<v Speaker 1>still import about a third of our processed parlite, we

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<v Speaker 1>get the rest from domestic mines in Arizona, California, Idaho, Nevada,

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<v Speaker 1>New Mexico, and Oregon. Once pearlite is taken from the ground,

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<v Speaker 1>processing plants crush the material into smaller pieces that are

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<v Speaker 1>more suitable for a variety of purposes. Then the popcorn

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<v Speaker 1>part comes in. Workers heat the pearlite to roughly one thousand,

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<v Speaker 1>six hundred degrees fahrenheit that's eight and seventy degrees celsius,

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<v Speaker 1>causing the water within to expand rapidly into vapor. This

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<v Speaker 1>creates a popcorn type reaction. The same principle that causes

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<v Speaker 1>the kernels of popcorn in your microwave to expand into

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<v Speaker 1>a delicious treat results in expanded parlite, a material that's

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<v Speaker 1>twenty times its original volume while being forty times less

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<v Speaker 1>dense and before it's popped, pearlite is usually gray, but

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<v Speaker 1>can be brown, green, blue, or red. Once it's expanded,

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<v Speaker 1>Pearlite is generally light gray to white. Structurally, expanded pearlite

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<v Speaker 1>is a light and airy with tiny bubbles and holes throughout.

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<v Speaker 1>It's low density and low price make it handy for

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<v Speaker 1>a variety of applications, like in lightweight plasters, insulation, ceiling tiles,

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<v Speaker 1>and concrete. It's perfect for noise insulation too, and the

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<v Speaker 1>fact that it's non flammable makes it safe for use

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<v Speaker 1>in many types of construction. Parlite is also widely used

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<v Speaker 1>in the beverage industry as a filtration agent, particularly for beer.

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<v Speaker 1>In its puffed form. It assists filtration by fighting clogs

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<v Speaker 1>that would otherwise shorten a filter's life. But for many

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<v Speaker 1>of us, especially anyone who's started a quarantine garden, pearlite's

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<v Speaker 1>unique properties are most apparent when it comes to gardening.

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<v Speaker 1>About ten percent of the world's pearlite use goes towards

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<v Speaker 1>horticulture every year. We also spoke by email with Melinda Meyers,

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<v Speaker 1>a horticulturist and gardening expert. She said Parlite is sterile, lightweight,

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<v Speaker 1>and contains lots of tiny air spaces, increasing air and

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<v Speaker 1>soil and improving drainage. When making my own podding mix,

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<v Speaker 1>I use one part Parlite, one part compost, and one

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<v Speaker 1>part petmas. You may need to try a few mixtures

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<v Speaker 1>to see what best fits your gardening and watering styles.

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<v Speaker 1>Like any recipe, the proportions may be adjusted for the

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<v Speaker 1>way the gardener likes to water and care for plants

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<v Speaker 1>and the type of plants they're growing. Tronfeld recommends making

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<v Speaker 1>Perlite ten to thirty of your potting mix, depending on

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<v Speaker 1>the intended use and other ingredients you have. He said,

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<v Speaker 1>for example, higher percentages are helpful in seed starting mixes

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<v Speaker 1>and for growing plants with root rot issues. Root rot

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<v Speaker 1>is directly related to water drainage. Aeration is another critical

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<v Speaker 1>factor in growing all kinds of plants because roughly of

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<v Speaker 1>the oxygen that plants absorbed from their environment happens through

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<v Speaker 1>their root systems. That's why some savvy homeowners also scatter

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<v Speaker 1>pearlite over their lawns. Pearlite naturally works its way through

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<v Speaker 1>the soil, preventing root rot and increasing aeration, resulting in healthier,

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<v Speaker 1>more resilient grass growth. But pearlite isn't the only way

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<v Speaker 1>you can improve your soil quality. Pummice, rice hulls, and

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<v Speaker 1>vermiculite have similar qualities, but they have characteristics that vary

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<v Speaker 1>depending on the issues you're wrestling with. Perlite, for example,

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<v Speaker 1>is best for situations when you want very good aeration

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<v Speaker 1>and drainage as well as good water retention, and depending

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<v Speaker 1>on your needs, you can blend pearlite with a variety

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<v Speaker 1>of substrates to create soils that are perfect for different

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<v Speaker 1>plant species. Myers says that peatmas, pine bark, and coconut

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<v Speaker 1>fiber are all commonly paired with pearlite, and just moistened

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<v Speaker 1>pearlite before adding it to any soil mix, and wear

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<v Speaker 1>a mask when you work with it. Both of these

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<v Speaker 1>steps will help prevent you from inhaling small particles of

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<v Speaker 1>pearlite that could put you at higher risk for certain

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<v Speaker 1>lung diseases in the long run. Today's episode was written

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<v Speaker 1>by Nathan Chandler and produced by Tyler Clay. For more

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<v Speaker 1>on this and lots of other growing topics, visit how

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<v Speaker 1>stuff works dot com. Brain Stuff is production of iHeart Radio.

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<v Speaker 1>For more podcasts my heart Radio, visit the iHeart Radio app,

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<v Speaker 1>Apple Podcasts, or wherever you listen to your favorite shows.