What is Vermiculite?
Vermiculite has been used in various industries for over 80 years. It is used in the construction, agricultural, horticultural, and industrial markets. Vermiculite is the mineralogical name given to hydrated laminar magnesium-aluminum-ironsilicate which resembles mica in appearance. Vermiculite is found in various parts of the world. Locations of the predominant commercial mines are in Australia, Brazil, China, Kenya,Vermiculite South Africa, USA and Zimbabwe. Vermiculite mines are surface operations where ore is separated from other minerals, and then screened or classified into several basic particle sizes.
When subjected to heat vermiculite has the unusual property of exfoliating or expanding into worm-like pieces (the name vermiculite is derived from the Latin 'vermiculare' - to breed worms). This characteristic of exfoliation, the basis for commercial use of the mineral, is the result of the mechanical separation of the layers by the rapid conversion of contained water to steam.
Vermiculite's many uses and beneficial properties include:
Vermiculite is an odorless, fireproof mineral substance. Along with another naturally occurring substance, perlite, it's often added to potting soil. Vermiculite provides many benefits. These include:
* Improves aeration: It loosens the soil so roots can more easily reach down and grow through the soil.
* Adds permanent soil conditioner: Unlike compost, which eventually breaks down into the soil, vermiculite doesn't break down. Compost does add vital nutrients, but if you need to permanently improve drainage, vermiculite is a great solution.
* Slightly raises pH: Vermiculite is pH neutral, around 7.0 or so, but because of some compounds found within it, it can slightly raise pH, a plus for acidic soils
* Makes other minerals available: Vermiculite naturally reacts with soil compounds and makes available other nutrients such as calcium, potassium and magnesium.
Most commercial potting soils come premixed with vermiculite, so there's no need to add it. When you spread a bit of soil out, you can see white beads in the mix. Check the ingredient label. You're either looking at vermiculite or perlite. You can purchase bags of horticultural-grade vermiculite and work it into garden soil according to the package directions too.
How is it used in gardening?
Vermiculite is most frequently used in conjunction with perlite as the two complement each other well. Vermiculite retains moisture (about 200% - 300% by weight), and perlite doesn't so you can balance your growing medium so that it retains water and nutrients well but still supplies the roots with plenty of oxygen. A 50/50 mix of vermiculite and perlite is a very popular medium for drip type hydroponic systems as well as ebb and flow systems. Vermiculite is inexpensive.
The major drawback of vermiculite is that it retains too much water to be used by itself. It can suffocate the roots of plants if used straight.
Seed Germintation
Vermiculite is ideal for the germination of seeds, because it's aeration properties combined with it's water holding capacity make it a very suitable medium for direct contact with the seeds.
When vermiculite is used alone, without compost, seedlings should be fed with a week fertilizer solution when the first true seeds appear. 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. Then plant them singly in small pots or trays of potting compost. Vermiculite can also be applied to the outdoor seed bed where it will give improved emergence and less risk of capping
Rootings/Cuttings
Vermiculite/sphagnum moss peat composts stimulate root growth, giving quicker anchorage of the plant and uptake of nutrients.
A 50/50 mix is generally suitable for cuttings on the open bench or under plastic covers, but a maximum of 25% is recommended under mist irrigation in Summer.
Thoroughly water the vermiculite before inserting cuttings, and do not compress around the base of the cutting.
Potting Mixes
Vermiculite in potting compost gives a very light open compost, holding more water and facilitating re-wetting, thereby lengthening the time between watering. Vermiculite also has excellent ion exchange properties which absorb excess nutrients and release them slowly to the plants via the finest root hairs.
A 50/50 mix of vermiculite and sphagnum moss peat is widely used for greenhouse pot plants and hanging baskets, while a 25/75 mix is generally suitable for for bedding plants, nursery stock, etc.
To improve an existing compost add 20-25% by volume of Vermiculite and mix thoroughly.
Excerpts taken from the following websites
http://www.thegardensuperstore.co.uk/ve ... garden.htm
http://garden.lovetoknow.com/wiki/Vermi ... _Gardening
