Kitchen Garden Forum

I always thought that they were the same difference and whichever was the cheaper at the time,I bought to add to the compost in my pots etc,now I find that they are similar yet different.
Vermiculite is water retentive,holds nutrients,aerates compost and has an alkaline Ph.
Perlite doesn't hold as much water as Vermiculite so not as good holding nutrients,can be powdery(allergies) but is a better medium for mixing with compost when striking cuttings and is Ph neutral and better (when crushed) when used to cover small seeds on the surface of the compost.
It does seem to be a bother to keep both when they are both so similar.Is there a situation where one should have preference over the other for general use?

Hi Snooky,
As a retired nurseryman I would say that you really want both but of course I had to use both for the jobs you have mentioned.
Vermiculite is certainly best for laying over a seeded tray and there are certain times when cuttings have to be produced in Perlite and nothing else eg, rooted cuttings to the USA and South Africa where neither countries allow foreign soil. But I suppose on an allotment there is little call for such cuttings. Of the two and I had to choose it would be Vermiculite. Incidentally I think that both mediums hold twice their own weight of water when saturated.
JB.

I am glad you asked that question Snooky as I would also like to know. I have used both this year but this year I have had very poor germination of most of our seeds. I bought a bag of compost from Gordon Riggs which when opened was fabulous to handle, very fine compost. But I had very poor germination and my beans were very slow germinating and there were quite a few misses.

I prefer vermiculite to sprinkle over seeds, but use perlite to lighten potting compost. I've just looked them up and vermiculite also contains potassium and magnesium and is able to absorb fertilizers which can then be released back for the plants to use.

You can get different grades of vermiculite, so the fine one is best for covering seeds, but you could use a coarser one mixed with compost to lighten it. Perlite just gives a more open compost for drainage purposes.