If you ’ve ever purchase potted plant or veggie starts , or opened a bag of commercial potting mix , you may have noticed tiny white balls in the soil that look like Styrofoam bite .
These white ball are actually crucial filth components called perlite , and they ’re not simply fillers or artificial sway as some masses might believe .
What is perlite?
First , lease ’s go over what perliteisn’t : Perlite is not a type of soil , it ’s a territory additive that can also be used as a grow medium .
Perlite isnota plant food , and has no nutritionary or microbic value to plants or grunge . Its benefit are derived alone from maintain the grunge structure loose and weak .
What perliteis : an inorganic , non - toxic , lightweight stain amendment . But do n’t let the “ inorganic ” part deter you if you ’re an constituent gardener ! ( More on that below . )
Also cognize as expanded pyrite , perlite is a mined volcanic rock that is mixed into many industrial building intersection for stableness , such as masonry building , loose - fill insulation , cement , and plaster . It ’s also used as filter media for swimming pond filters , and as a filter aid for beverages ( like juices , beer , and wine ) and for waste water .
In the gardening world , perlite is used to improve soil social organisation by provide drainage and aeration . “ Air for the soil ” is what I like to call it , and it ’s the next best matter to compost for circulating breeze between the roots for potent , healthy plant life growing .
Look under a microscope and you ’ll find that perlite is take with many midget cavity that declare piss ( like a sponge ) , making it efficient at deliver moisture to plant radical . All these nook and crannies enableperlite to hold three to four times its weight in body of water .
It ’s also capable of storing nutrients for a short menstruum when they otherwise might wash away forthwith .
At the same time , the cavities mean perlite is quite porous , so it drains excess water more pronto thanvermiculiteand other potting media . This is a beneficial affair , since hold back your dirt from becoming waterlogged is the number - one way to preclude antecedent rot and fungal disease .
revelation : If you shop from my clause or make a leverage through one of my links , I may receive direction on some of the Cartesian product I urge .
How perlite is made
The perlite we see in potting mix is often called “ volcanic Zea mays everta , ” and for good reason .
direct out of the ground , perlite is a dense , formless volcanic glass with very gamy water content . In its natural DoS perlite is brown or black in color , as it ’s typically formed during the cooling process of lava that produces obsidian .
During processing , raw perlite is superheated very rapidly to temperatures of 1560 ° F to 1650 ° F , which have the material to soften and the wet inside the glass to turn to steam . As the trapped wet inside house of cards , trying to turn tail , it expands the material from 7 to 16 times its original size of it — much like Zea mays everta pop .
The amplify stuff turns blanched due to the reflectiveness of the snare bubbles , and the result perlite is a chemically sluggish , aseptic textile that takes on an ultra jackanapes , bubbly texture .
Is perlite organic?
To call something constitutive depends on your personal feeling ( and here , it ’s merely a instance of semantics ) .
From a chemistry view , organic compounds contain carbon . Since perlite does not incorporate carbon paper , it ’s view an inorganic cloth .
But from a horticulture view , the terminal figure “ organic ” refers to something that is naturally create without synthetic cognitive process or significant chemical substance changes .
It ’s rightful that perlite has to be “ pop ” in an industrial process that flex it into the lightweight fabric we see and know , but it is still a course occurring mineral that ’s extracted from the earth . It ’s no different fromseaweed emulsionorfish fertilizerthat has to undergo some kind of process to be desirable for garden .
And officially , horticultural perlite is OMRI listed for use in organic agriculture , so you do n’t call for to care about what you ’re putting in the ground . It ’s beneficial for your plant , and it is n’t harmful to humankind ( as far as normal handling is have-to doe with — just do n’t breathe in perlite dust if you ’re sensitive to fine particles in the air ) .
How to use perlite for your plants
In potting mixes
Perlite is usually used in pot grime and soilless mixture ( particularly forindoor come starting ) to keep the dirt structure at large and well - draining without danger of compaction over prison term .
Depending on your plant ’s needs , a unspoilt place to start is having the perlite make up around 10 per centum to 30 percentage of the full volume of your potting mix .
For starting seeds
To make a clean , basicseed starting mixture , coalesce adequate parts perlite , vermiculite , and peat moss ( or coco coir ) . This soilless mixing help support healthy seedling development and reducesdamping off disease .
you may also start seed in moisten perlite only , or test the germination ofolder seedsin baggies filled with moistened perlite ( as an option to thecoffee filter method acting of start seed ) .
For humble seeded player , I recommend using finer grade of perlite ; though forseeds that need Inner Light for sprouting , you may step up to a intermediate - coarse perlite that will let the Lord’s Day shine through .
To propagate cuttings
you may use perlite to disseminate flora cuttings . Rather than just settle your cutting in water system , you’re able to settle it in a small jounce filled with moistened perlite .
To aerate garden soil
In raised bed or in - ground garden beds that have trouble with cakey clay ground , you’re able to improve drainage by raking in a 2 - in layer of perlite into the top 6 to 12 inches of ground , at the same metre you amend the territory with compost and other nutrients .
In heavier soils , stress adding perlite to yourgarlic planting bottom in fall , as the perlite helps keep bulbs from being waterlogged in wintertime and spring . Perlite also help the grunge dry out in the calendar week or two before yourgarlic crop is ready for harvest .
Because it does n’t break down , a exclusive app of perlite can keep the planting bottom light and loose for several years ! ( Over time , other constitutive topic like compost , mulch , and tooth root systems will deepen the grease composition course . ) It was my “ clandestine factor ” during my years ofgardening in Southern California , when I call for something more than just compost to stop up all the hard dirt clods in our beds .
To amend bagged soil
Some ( but not all ) commercial-grade potting soils and bagged garden soil profit from having more perlite add up to the mix .
This is especially beneficial fordeep - settle plantsthat are more rich when the roots do n’t have to push down into dull , compact grunge ( retrieve rootage veg like carrots and daikon — you’ll see how my previous clay dirt was notorious for turning outdeformed carrot ) .
Quick Tip
think back that perlite does n’t break down , so once you add it , you ’re permanently changing the structure of your soil . It ’s good to start with a footling and bring more over sentence as call for .
Perlite is an essential soil conditioner that Ialwayskeep on hand , and I buy a few udder every year as I always determine a economic consumption for it .
Grades or sizes of perlite
Perlite is typically usable in four grades or granule sizes , which agree to coarseness level .
Super vulgar and coarse perlite : This type of perlite is often used to amend raised bed and garden layer , or dense grunge with high water - hold capacity ( clay ) . Size # 4 perlite is a whopper of a particle that should only be used for super lowering soil .
average perlite : You’ll mostly see medium - grade perlite in commercial potting dirt . It ’s a good all - around size for potted plants , windowpane boxful , and cosmopolitan garden use .
Fine perlite : These smaller corpuscle are ideal for start seeds or rooting cutting . okay perlite is tough to find in this size as a standalone intersection , so I tend to go withfine pumice stone , which is unremarkably labeled for bonsai or succulent planting .
Be aware that modest grades of perlite , and in some cases cheap perlite with little quality control , can get dusty ( specially as you get to the bottom of a dish ) . If you ’re sensitive to o.k. particles in the air , be certain to wear a junk masque and/or safety field glass when you ’re handling perlite .
Benefits of using perlite in the garden
Perlite is a highly utilitarian element of garden for many reasons :
Because of these belongings , perlite is also democratic in orchid , cactus , andsucculentplanting mixing that wish to be on the drier side , and in hydroponic setup as a standalone growing medium .
Does perlite cause fluoride burn in plants?
There ’s a hearsay that perlite is responsible for fluoride burn mark in houseplants , which appear as brown folio topographic point or scorch foliage gratuity in susceptible plants like dracaena , wanderer plants , and Easter lily .
If you ’re using a commercial potting soil that contain perlite , however , the chances of that happening are very slender .
atomic number 9 toxicitycan be due to many thing , including fluoridated water , superphosphate fertilizers , low soil pH , and other environmental conditions that have little to do with pot sensitive that merely has perlite in it .
Where to buy perlite
The most convenient source of perlite is your local independent garden center or big - boxwood works nursery . When buying perlite , verify you are buying 100 percent perlite and not a soil or soilless blend .
I ’ve also linked my favourite stain of perlite ( below ) in a multifariousness of size , which you may easily buy online .
If you ca n’t find perlite locally , pumice stone makes a good reserve as it has similar qualities . Sometimes you’re able to use vermiculite in a exigency ( specially as a seed starting medium ) , but keep in idea it retain more moisture than perlite does .
When it comes down to it , perlite is still the best choice for a soil amendment when you require moderate weewee retention , excellent aeration and drainage , and retentive - condition benefit .
Where to buy
Perlite
Perlite alternatives
Try pumice or rice hulls
Pumice ( another mined mineral ) and rice Isaac Hull ( the hard out coverings of rice grain ) are both good alternative to perlite , as they work in the same way to aerate soil .
pumice stone , in finical , is a popular 1 - to-1 reliever as it ’s easier to recover . A benefit of pumice stone is that it ’s heavier , so it does n’t swim or bollix forth as well as perlite . Pumice also work out well in pot mixes for tall plants that might postulate a footling extra weight on the bottom to keep them from tumble over .
Can you use Styrofoam instead of perlite?
Do n’t do this at home ! ( Or anywhere , for that topic . ) Despite how likewise it looks and behaves compare to perlite , Styrofoam is not the variety of stuff you need to add to your garden permanently ( especially an edible garden ) .
As it sits in the soil , Styrofoam will leach microscopic phenylethylene and other harmful chemical that linger for centuries , and you ’ll never get rid of it in your environment .
This post updated from an article that originally appeared on February 13 , 2020 .
