Vermiculite is a mineral substrate belonging to the mica group.
It is a hydrated phylosilicate consisting of lamellae, which is obtained by exfoliation of minerals such biotite or phlogopite, a phenomenon of expansion occurs under the effect of heat.
The interstitial water evaporates by rapid warming and the pressure spreads the lamellae apart.
The name vermiculite is derived from Latin vermicularis (like a worm) because of the elongated and twisted columns formed by exfoliation.
There have been cases of contamination by asbestos, primarily in the United States where the main mine was closed. Vermiculite currently sold is regulated and should not contain asbestos.
- very high water absorption capacity:
- 200-300 % of its own weight
- 20-50 % of its own volume
- very light
- suitable for bulbous plants or plants with thick roots
- can be used outdoors
- very suitable for sowing and cutting
- chemically active
- so light it can fly away with the wind
- the structure is fragile and deteriorates over time
- risk of clogging of drains in active hydroponics systems, requires a filter
- vermiculite can be used on its own for:
- culture of bulbs or root vegetables like carrots
- vermiculite can be mixed with perlite for a better balance between water retention and ventilation
- vermiculite can be mixed with potting soil for better aeration and water retention
Watering can happen in either of 2 ways:
- from above, till the water flows out of the bottom of the pot
- from below: water will be sucked up by capillarity