Westland Gro-Sure Vermiculite 10L Naturally occurring material Lightweight Helps retain moisture Helps retain nutrients Provides insulation for healthy seed germination Vermiculite absorbs nutrients, preventing them from being washed out & then releases them as required to plant roots. It helps to retain water & holds moisture near to plant roots. Vermiculite is a naturally occurring, non-toxic material that has been heated to a high temperature to produce a lightweight material with a high surface area. It has an attractive golden colour with a typical particle size of 2-5mm.