Both vermiculite and perlite are inorganic products, both are relatively sterile, and both are often used as soil additives. Vermiculite is a soft,spongy material made from super-heating mica. Perlite is a hard, highly porous material made by super-heating volcanic glass. Typically, vermiculite will be tan/brown in color and perlite will be white. Whereas vermiculite absorbs water in its plate-like structure, perlite traps water in its very porous, undulated structure. Vermiculite is close to a neutral pH whereas perlite has a slightly more alkaline pH. Both are very light-weight. Though both products do in fact aerate the potting soil, the fact that vermiculite holds moisture longer than perlite makes their usage different. Vermiculite retains more water and retains it for longer periods than perlite. Vermiculite affords slightly less aeration than perlite. For plants that thrive growing in a more-wet soil, vermiculite would do well as a potting soil additive. Many plants are more sensitive to alkaline conditions, so in that case, vermiculite would be a better choice than perlite. Since many foliage plants appreciate more water-retentive potting soil, they do well in a vermiculite-added potting soil. Also, simply because of its water retention/nutrient retention, vermiculite makes a good seed-starter medium. Perlite only traps water on its large surface area, consisting of nooks and crevices, and thus releases its water more quickly. In doing so, it can help raise the humidity around plants. While vermiculite would be a better choice for starting seeds, perlite would be a better choice when rooting cuttings. Cuttings would tend to rot more easily in vermiculite. For plants that need a quickly draining soil, a soil that does not retain much moisture, a soil that is extremely well aerated, and a soil that could have a higher pH, perlite would be the best additive. Cacti and non-cacti succulents would be such plants. Also, because most epiphytes like to have their roots dry out quickly between watering and also appreciate higher humidity, perlite would be the best choice. Thus, although vermiculite and perlite have some similar properties, they are not the same. When plants need more water-retentive soil or for seed-starting, use vermiculite. For plants that prefer quick-drying soil or for starting cuttings, use perlite. Are Vermiculite and Perlite the Same?
2 cubic feet is $16.97 for Perlite, $21.97 for Vermiculite both at Home Depot. I've never used it except in a pre-mixed potting soil. I probably should stock some since I am now using my large pile of horse potting soil... (which BTW grows bermudagrass very nicely, probably due to the ingredients) Rancher
Still learning gardening, and tried vermiculite, and the plants got root rot, so I quit using it. However I discovered that vermiculite is used in making refractory cement so my investment is not wasted. In stead of perlite, I'm using sand because it provides minerals the perlite does not provide, yet let's the water drain to some degree . I am doing a form of aquaponics so it's experimentation any way .
Vermiculite is also used in those buddy-wraps that you wrap around your neck to keep you cool in the summer heat. The stored water makes them plump like a sausage, but keeps you damp but cooler. (I use them, when the heat is bad.) (Iirc) there is roughly one table spoonful of dry vermiculite in each one of those neck wraps.
A couple months back, I got prices on both. They aren't cheap. But, both are less costly than the clay! (Prices are in USD.)
@Ganado, would you say Perlite would be the best option for ebb and flow beds, in an aquaponics system?
I would use both. but in a wet climate I would use more perlite than vermiculite. Having said that I will also qualify by saying it depends on what to are planting and if the plant need more or less moisture. I live in a dry climate so if I am potting low water needs plants (like a succulent such as sloe vers) I would use a 80/20 perlite vermiculite option along with spagmum peat moss Global Buckets has some of the best information on potting soil mixing. You can adjust from there for your climate and plants. Gardening isn't an exact science. it's an experiment which is why I agree with people who post, practice practice practice. How you garden changes over time. I have gone from neat rows and wood raised beds to key hole gardens and now I have hugelkulture beds started as I try to create high moisture micro environments in my yard. My goals are different now. at 1st I just wanted fresh veggies, now I garden for long term sustainable food. so my garden looks wild and untended. plants are grown in rotation and some I let seed themselves and plant the rotation crop on top of them. I do have everything labeled and plotted on paper but it does not look as neat as the paper lol Finally, your goals maybe different than mine. So what I do may not apply to you. I try to share what I know not as an absolute truth but ore of as a place to start. I have been working on a plant compatibility chart for companion gardening. haven't had time to finish it but will post in next 2 weeks or so
Don't mean to topic drift, but Vermiculite also retains heat VERY well. I use it to surround cast steel and iron castings that have been repaired so that they cool slowly. So slowly in fact that often times a large casting buried in the box of vermiculite will still be too warm to touch bare handed after 24 hours.
Not sure it would be the best for plants then, in an aquaponics system in Southeast Asia? My issue will be keeping the water cool enough.
I believe, but do NOT know, that vermiculite is porous enough to allow evaporative cooling. Both vermiculite and pearlite are excellent thermal insulators when kept dry With a water flowing system, heat retention should not present a big problem, if you have a way to keep the water cool, say like in a shaded "waterfall" (aka cooling scheme of some kind.) You will need to ensure that the evaporation doesn't let any contaminants concentrate; you'll need a bleed and feed method to keep the plants happy.
