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Organic Grow Mediums

Nico Escondido

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When it comes to cannabis cultivation, especially medical marijuana, many growers are interested in using organic mediums. However, there are always debates about what constitutes an organic grow medium, particularly if the garden is indoors.

Typically, indoor hydroponic gardens make it difficult for growers to use organic mediums, especially if the irrigation is not a top-feed system. And while popular hydroponic mediums such as mineral wool (Rockwool) and HEC (hardened-expanded clay) are developed from organic material, they generally are not considered organic due to their synthetic manufacturing processes.

This leaves us with soils, or what are commonly referred to as “soilless” mixes in the world of horticulture. These mixtures usually contain only organic matter, but there is some debate here, too, depending on the ingredients of the mix. This concern then leaves growers asking one simple question: What is a soilless mixture?

Soil & Soilless Mixtures

To start, let’s clear up some common misconceptions when it comes to organic soil mediums.

Regular soil, also referred to as topsoil or mineral soil, is simply regular ol’ Earth soil. However, real Earth soil does not do as well in a plant container indoors as it does outdoors. This is mostly because Mother Nature helps to naturally provide insects and decaying organic material, as well as naturally occurring microbial agents that help give the soil the nutrients and trace elements it needs to be beneficial for plant growth.

Once we move indoors, soil mediums change to artificial soilless mixtures that still contain organic soil components, but may also have other synthetic additives and nutrients mixed in. Though technically organic, these grow mediums are processed and do not occur naturally, thus contributing to the argument over whether soilless mediums are organic or not. Additionally, these mixes sometimes have synthetic additives that help the mediums to retain moisture or aerate more easily. Therefore, it is important to carefully examine all product labels to ensure you are purchasing the desired medium.

Still, these soilless mixtures are almost always sphagnum/peat moss-based (hence the term “soilless”) and look almost identical to real Earth topsoil. Mixed in with these mossy bases, soilless mixes often feature other organic additives that may include loam and humus, both of which contribute to the base texture. Loam and humus are basically broken-down organic matter that have reached full and stable decomposition, much like compost, and can be derived from sand, clay, silt or other decaying matter like leaves or wood. These essential components also feel, look, and act extremely similar to topsoil.

Other popular additives, such as perlite and vermiculite, help the soilless mediums hold water and stay moist but also create a porous environment for the medium that allows air to easily penetrate the soil. This is especially important in the root zone where the roots absorb oxygen. It is these types of important additives raise questions about a medium’s organic credentials. While both of these additives are naturally occurring minerals, they usually undergo industrial processing (in the form of heating) to give them a more stable form. Stricter interpretations of organic matter sometimes negate organic certification for these types of synthetic additives.

Soilless mixes are usually considered organic medium by most people and are a very popular choice among new cannabis growers. Of all the grow mediums available today, soilless mixes are best suited for amateurs as they are the most forgiving, providing excellent “buffering” for roots against fertilizing mistakes. Soilless mixes also offer low levels of nutrients already mixed into the medium, making them ideal for seedlings or clones that are too young for stronger feeding programs. Additionall, they provide a soft “nest” for growing root systems that may find other hydroponic mediums rough to navigate.

Lastly, always remember to first add a base layer of gravel or small rocks to the bottom of your potting containers before filling them with soilless mixes. This will aid greatly in drainage and aeration within the root zone, preventing air and drain holes at the bottom of your containers from getting clogged.

Thanks for reading everyone and remember: Grow… And help the world grow, too!

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