Vermiculite is a natural mineral ore that has been heat treated to expand into a light, spongy worm like, inert substance. Vermiculite is made from mica whereas perlite, a similar gardeners aid is a type of highly porous volcanic glass. Because vermiculite is permanent, clean, odorless, non-toxic and sterile and very light it has many uses for gardeners.
Gardeners Uses of Vermiculite
- Vermiculite greatly improves seed compost by promoting aeration and drainage, important for seeds and cuttings.
- Vermiculite improves germination and reduces the risk of damping off when applied as a thin layer on top of your sown seeds.
- A 50:50 mix of compost and vermiculite is ideal for the germination of seeds, because it’s aeration properties and water holding capacity make it a suitable medium for direct contact with the seeds.
- Vermiculite used alone without compost helps germination but seedlings should be fed with a week fertilizer solution when the first true seeds appear. I have some African Violet seeds being grown this way at the moment.
- Large seeds can be mixed with Vermiculite in a small polythene bag closed at the neck, and kept in a warm place until the seeds just start to germinate.
- Vermiculite can be mixed into compost for taking cuttings.
- Mixed with compost vermiculite can also store Dahlia and Begonia tubers through winter.
- Slower germinating seeds should be covered with grit in preference to vermiculite.
- For fine seeds it can be ground down finer that that shown above.
- Mix with peat or coir to make a soilless growing medium for the home gardener to promote faster root growth and give quick anchorage to young roots.
- Vermiculite is also used as a growing medium for hydroponics.
- Heavy sticky soil can be conditioned by the addition of vermiculite.
- Available from good garden centres
Vermiculite for Cuttings
- Vermiculite 50% sphagnum moss peat 50% compost stimulates root growth, giving quicker anchorage of the plant and uptake of nutrients.
- Thoroughly water the vermiculite before inserting cuttings.
- Do not compress around the base of the cutting.
- Vermiculite gives a very light open compost, holding more water and facilitating re-wetting, thereby lengthening the time between watering.
- Vermiculite absorbs excess nutrients and releases them slowly to the plants via the finest root hairs.
- Use a lower proportion of vermiculite under mist irrigation in Summer say 25%.