Posted: 29/03/2013 at 23:16
Perlite acts similar to vermiculite.
Where as vermiculite is usually spread on the top of seed compost and the first one or two potting up stages, to improve germination and reduce damping off. Perlite mixed in compost retains moisture by improving aeration and drainage. Roots need air to take up nutrients from the compost and perlite assists with this.
I use perlite mixed with compost for plants in pots instead of the water retaining granules. Whilst you can get by without it, using it does give plants a better growing media and reduces the need to water pots daily in hot weather. I'm very optomistic, me thinks we will get some warmer weather.
Shop around, it can be expensive. Wilkinsons are probably one of the cheaper places to buy perlite, I purchase mine at a local nursery at a fraction of the cost in the GC.