Growing Media

Coco coir and perlite constitute the media we cultivate our plants in. First, we sterilize the media using chlorine dioxide (ClO2), then we inoculate the media with mycorrhizae. We also provide lab results of our media both before and after sterilization!

January 6, 2017 // GA_Team // No Comments // Posted in Process // , , , , ,

Plants grow in soil right? Yes, but not always! Plants don’t actually need soil – as far as the roots are concerned, they need water, oxygen, nutrients and physical stability. The general term we use for the “stuff” that plants grow in is “growing media.”

coco_perlite_2If it seems a little obtuse to want to grow plants in anything but soil, but it turns out that there are some amazing (and often eco-friendly) alternatives out there that confer a whole host of additional benefits to plants, including a cleaner environment, less prone to pests and diseases, and more control over the water, oxygen and nutrients available to the plants.

At Golden Apple Cannabis Co. the growing media in use is a combination of coco coir and perlite. We use a mixture of 60% coco coir and 40% perlite to make up our growing media. A few considerations were taken into account when deciding the ratio of mixture such as the following:

Cation Exchange Capacity – CEC which is the ability of a growing media to hold on to and release positive charged elements (cations) in nutrients. This is a very crucial consideration when choosing growing media. Growing media with a low CEC allows cations to be easily leached away whereas growing media ­with a high CEC withhold cations and act as a longer-term cache.

Air Filled Porosity (AFP) which is the amount of air space in the growing media.

Water Holding Capacity (WHC), the ability of a growing media to hold and store water.

We’ll dive a bit into both coco coir and perlite a bit more (and a few other things):

Coco Coir

coco_coirAs the by-product of coconut harvesting operations, coco coir is a renewable resource that has become a popular, effective grow medium. For the professional coconut industry, the husk of the nut has traditionally been a waste product. Coco coir is harvested year-round continuously. Environmental considerations notwithstanding, coco coir has many benefits for the grower—it retains water and is airy. Dating back to the early 1970s, innovative growers in the Netherlands repurposed coconut husks into coco coir. Today, one-third of professionally grown roses are grown in coco coir.

Benefits of coco coir are as following:

  • High water holding capacity
  • Acceptable pH & EC after it is rinsed and sanitized
  • Excellent wettability, superior to peat
  • Ability to retain nutrients against leaching and to buffer supply
  • Unique water holding capacity
  • Good drainage / aeration
  • Less shrinkage
  • Retains physical properties longer
  • Light weight
  • No pests, weeds, or diseases
  • Odorless and pleasant to handle
  • Natural and renewable resource
  • Uniform in composition
  • 100% Organic
  • Promotes strong root growth and plant vigor.
  • Absorbs water readily and re-wets easily, thus reducing the need for wetting agents.
  • Reduces watering frequency without plant stress, thereby reducing labor costs and minimizing plant loss
  • Increases shelf life of plants
  • Slow breakdown of material means product will not shrink during your growing cycle
  • High water holding capacity while still maintaining excellent drainage and aeration


Perlite is a form of glass; specifically a volcanic glass that is mined and then heated in big ovens until it ‘pops’ into a round, white material. The super heated perlite is comprised of tiny air compartments. Under a microscope, perlite perliteis revealed as being covered with many tiny cells that absorb moisture on the exterior of the particle, not inside, which makes it particularly useful in facilitating moisture to plant roots. In addition, when used in potting mixtures it can lighten the growing media, allow more air around the roots of plants and to both help retain water and improve drainage.

Grow Media Processing and Sterilization

Coco coir from a processor can contain contaminates and be full of salt. It is not recommended to use coco coir straight from a bag or brick due to these issues. Also, perlite can have a lot of “perlite dust” on the perlite pieces. This “dust” can be harmful to humans and their lungs, plus it is not a good addition to the growing media. It can turn to an unhealthy sludge in the pot.cl02

Therefore, the first step we take for growing media processing is to rinse, then sterilize the coco coir and perlite. We us a flushing and rinsing technique using chlorine dioxide gas (ClO2). The Chlorine Dioxide (ClO2) used is not to be confused in any way with swimming pool Chlorine, or industrial strength applications of low grade ClO2.

We use a 50 ppm ClO2 solution to thoroughly sterilize our media to kill any potentially harmful biological organisms, pathogens, spores, and any insects such as aphids, fungus gnats, etc. that might be present. It is common for growing media to pick up these potentially devastating contaminants while either in the manufacturing process, sitting in storage before being sold, or during transportation. The growing media is then thoroughly rinsed with reverse osmosis water to ensure no salts or ClO2 is left behind for the plants to uptake.

Mychorrizal Inoculum of Growing Media

Once the growth media is sterilized and rinsed with reverse osmosis water (nearly 0 ppm) we then add beneficial bacteria to the media. We use a mycorrhizae which is a natural and organic species of beneficial soil fungi that mycorrhizaecreates a “sponge-like” mass which collects and stores nutrients and water, increasing the uptake of both. We use a single species of arbuscular mycorrhizal fungi which contains only Rhizophagus intraradices, formally known as Glomus intraradices.

Mychorizzae are shown to have many beneficial effects in a growing environment; namely providing a biological connection between the roots and the soil and extending the plants’ ability to search for nutrients and water.

Mychorrhizal Inoculum is a soil fungus. Once it has been applied to plant roots, this fungus will colonize the root endo_myco_2system and carry on living for the life of the plant. The Mychorrizae spread thin fungal filaments called ‘Hyphae’ from the roots through the growing environment. These filaments reach far beyond where the root hairs of the plant can reach and give the plant access to otherwise inaccessible nutrients and water.

Mychorrizae also help protect the plant from pests and disease by naturally producing arbruscules that contain disease-suppressing phenols. Whenever a root pathogen tries attacking the root system, the arbruscules release a fungicide to eliminate the pathogen.

Lab Tests

The following are the lab results of our unsterilized media. This is simply the 60% coco coir and 40% perlite mix before the sterilization and inoculation process:


After the sterilization and mychorizzae inoculation process we then get the media tested to ensure that it is ready to be used for transplants. The EC value (amount of salts) is low enough as to not be toxic to the plants and we know exactly what we’re working with. This data is then used in conjunction with water test results to then make our own in-house custom nutrients!