Vermiculite is a popular hydroponic media favoured for its affordability and ease of use.
It is made from a natural mineral that expands with the application of heat. The expansion process is called exfoliation which takes place in purpose built commercial furnaces.
Vermiculite is very lightweight and sterile.
It has excellent water retention and capillary action properties, which allows it to be fully hydrated simply by applying moisture from above or below.
When used in hydroponics, vermiculite is often mixed 50/50 with coarse perlite if the media becomes too water logged. This improves aeration and drainage.
In hotter climates vermiculite is often used by itself because of its higher water holding capacity.
Vermiculite can break down after a period of time so is favoured for short term crops such as lettuce.
Growers who use vermiculite usually have a system in place where they manually fill NFT growpots or cell trays with the media. A seed is then inserted into the top of the media and the pots and trays are placed into a propagation system like an Ebb and Flow table where they remain until the seedlings have emerged and are at a reasonable size for transplanting into the main growing system.
The root system of the seedling holds the media together as much as possible so individual root bound ‘plugs’ can be removed from the propagating cell trays and placed directly into the plant holes of an NFT gully if required.
When Vermiculite is used in NFT growpots, the media filled growpot is placed into the plant hole in the NFT gully and the pot holds the loose media together and acts as additional support for the plant. The growpot also prevents sunlight entering the gully which can promote algal growth.
The larger volume of a growpot compared to a smaller cell tray plug, allows the seedling to be accommodated in the nursery area to a much larger size. This reduces the time it needs to spend in the main growing system = more crops per year. It is not efficient to have small undeveloped seedlings occupying valuable crop space in the main NFT system where plant hole spacings can range from 200 – 250mm centre to centre. It is better to have the seedlings held in a nursery system as long as possible so the leaf area can fill out before transplanting. The growth of the seedling then takes off more rapidly in the main NFT system due to the enlarged leaf area.
Characteristics of Vermiculite
- Inorganic, inert and sterile
- Non abrasive
- Ultra-light weight
- Free from disease, weeds and insects
- Slightly alkaline (neutralized with peat)
- High cation-exchange (or buffering exchange)
- Excellent aeration characteristics
- High water holding capacity
- Insulating
Vermiculite is available in the following grades:
- Grade 07 (0-0.5mm)
- Grade 1 (0-1mm)
- Grade 2 (2-4mm)
- Grade 3 (3-6mm) – Medium Grade – Most popular for Hydroponics
- Grade 4 (5-8mm)
Vermiculite is available in the following bag sizes:
- 10 Litre Bags
- 20 Litre Bags
- 100 Litre Bags – Loose
- 100 Litre Bags (24 Bags per pallet) – Please contact us for a Commercial Grower Discount.
