Vermiculite - How helpful can this mineral be?

Benefits

• High water holding capacity
• Good air holding capacity
• Non-abrasive and non-irritant
• Attracts excess nutrients
• Facilitates re-wetting
• High cation-exchange capacity
• Neutral alkalinity
• Does not deteriorate in storage (if kept dry)
• Free from disease, weeds and insects
• Insulates and minimises soil temperature fluctuations Inorganic and sterile
• No known toxicity or fire hazard

Uses of vermiculite

Seed Germination
Vermiculite is ideal for the germination of seeds because its aeration properties combined with its water holding capacity make it a very suitable medium for direct contact with the seeds.

For use pure, without compost, seedlings should be fed with a weak fertiliser solution when the first true leaves appear.

For use pure with large seeds, mix the seeds with vermiculite in a small polythene bag. Secure the bag at the neck and keep it in a warm place. When the seeds just start to germinate, plant singly in small pots or trays filled with potting compost.

For outdoor seedbeds, vermiculite can also be applied to give improved emergence and less risk of capping.

Potting Mixes
Vermiculite is used in potting compost to obtain a very light open compost that holds more water and facilitates re-wetting, thereby lengthening the time between watering. Vermiculite also has excellent ion exchange properties which absorb excess nutrients to then release slowly back to the plants via the finest root hairs.

For bedding plants and nursery stock, use a 25/75 mix. For improvement to existing compost, add 20-25% by volume vermiculite and mix thoroughly.

Rootings and Cuttings
Vermiculite can help to stimulate root growth, giving quicker anchorage of the plant and improved uptake of nutrients.

Thoroughly water the vermiculite before inserting cuttings, and do not compress around the base of the cutting.

For cuttings on the open bench or under plastic covers, use a 50/50 mix.

For mist irrigation in summer, a maximum of 25% is recommended.