When I started my garden I got all excited and got loads of stuff without really knowing what it was or why I needed it. You know how it is you go to the garden centre to get yourself a bag of compost, the next minute your leaving with 3 bags of compost, 10 packs of seeds, a new hose attachment, a cold frame, a new pair of gloves, 6 packs of bulbs and a bug house made of bamboo. Well on one of these trips I bought a bag each of perlite and vermiculite. I was going to get one but after about 20 minutes of going back and forth I just surrendered to the inevitable and bought both.
For a while I have put both into my pots and to be honest can’t say I have seen any difference. So I decided to actually do a little research and what I found shocked me to my very core… Not really but it was quite interesting… Ok this may not be that interesting but it will help me growing a few better plants. Now I know that they each work differently for different plants so you cannot actually compare the two.
Perlite for instance is a porous volcanic rock, it absorbs a lot of water due to its large surface area but allows excess water to drain. Being porous Perlite also holds air which helps aerate the soil.
Vermiculite on the other hand is an aluminium-iron-magnesium silicate “silicate minerals are rock-forming minerals, constituting approximately 90 percent of the crust of the Earth”.- Wikipedia. It can absorb up to 4 times its volume in water as well as attracting plant nutrients. It acts like a sponge and holds much more water than perlite but allows less aeration. It holds this moisture longer than perlite and keeps it close to the roots. It also means it absorbs excess moisture from around the root to stop mildew. Less watering is needed the more vermiculite you use.
You can actually grow most plants from seed in just perlite or vermiculite. Both holds enough moisture and allows in enough air to be used as a potting medium. They don’t provide any nutrients though so some form of fertiliser will be needed to be added once the plants start their first true leaves. It looks like vermiculite would be better for this as it holds onto the water longer. Perlite would dry out a lot quicker and need much more attention. I think I may give this a go I might pick some seeds and grow them; one in just perlite, one in just vermiculite, one in perlite-compost mix and one in vermiculite-compost mix.
From what I have learned I think vermiculite is better for plants as it holds water and nutrients close to the roots. Perlite is good for the soil\compost as it would help drainage and allow more air into it.
I will post my little experiment later.