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24 March 2021

The Best Medium for Beginning Cannabis Growers

First-time cannabis growers are faced with many decisions, such as what type of environment to choose or what kind of grow lights to implement, but perhaps none which will affect their growing adventure as significantly as that of growing medium. The medium you choose will ultimately depend upon as well as determine many factors in your cannabis garden, so it’s important to understand the various types, their benefits and drawbacks, as well as their most practical applications. There are many great options available to cannabis growers, but a few of the most popular include:

Soil

Coco coir (and coco mixes)

Hydroton expanded clay pebbles

Rockwool

Determining the Best Growing Medium for You

Deciding on the best growing medium can be tricky and usually requires making some important decisions first. For example, a gardener must first determine if they will be growing their cannabis plants indoors or outdoors. Another important consideration is whether the grow will be conducted hydroponically or not. Still, another consideration is the type and availability of light in a grow, as well as airflow. With all of the factors to consider, it can easily become overwhelming to know where to begin.

A Big Decision: Hydro vs Soil

One of the earliest determinations a grower will have to make, and one which will affect their decision on growing media, is whether they will employ hydroponics in their grow. Often referred to as “soilless” growing, hydroponic growers use mediums other than soil to anchor their plants and must supplement accordingly. Soil growers, on the other hand, are able to use a more straightforward approach to their gardening, similar to vegetable or flower gardeners.

Because soil already contains naturally-occurring nutrients in the form of compost and fertilizers, supplementation is not nearly as essential as with hydroponic systems. Whether growing in soil or hydroponics, your substrate will eventually need supplementation, another critical factor to consider when deciding on a growing medium.

Types of Growing Media

Once you’ve decided whether you will be growing hydroponically, it is time to select a medium on which to grow your plants. Let’s take a look at some of the benefits and drawbacks of some of the most popular media amongst cannabis growers.

Soil 

Soil has been and continues to be a standard in cannabis cultivation for a reason. It is easy to manage, natural, and recognizable to beginning growers as a typical gardening substrate. Potting soil mixes are widely available from both hydroponics stores and nurseries and are relatively inexpensive. Because soil is composed of composted organic matter and often supplemented with additional fertilizers, growers working in soil will need to feed their plants far less frequently than growers working in other media. While it touts many benefits, soil is not without its drawbacks as well.

Benefits of growing cannabis in soil

Nutrients – The presence of beneficial microorganisms will help your plants to thrive in their first few weeks after transplant with little or no feeding.

Beneficial Bacteria and Fungi – High-quality soil mixes generally contain various strains of beneficial bacteria, such as plant-growth-promoting rhizobacteria (or PGPR), a beneficial bacteria which helps protect plant roots from disease, assists in the uptake of nutrients, and aids in the synthesis of necessary compounds for the plant. Quality soil is also teeming with mycorrhizal fungi, which aids in the breakdown of heavy metals and organic compounds in the soil, as well as increasing soil’s water retention properties.

Water Retention – The presence of peat moss in most soil mixes makes their water retention capability outstanding, meaning you will not need to water as frequently.

Sustainable and Affordable – Soil is sustainable and affordable, especially when you mix your own at home. Many growers prefer to create their own super-soil from scratch, combining various elements and allowing them to compost to create a microbial-rich soil mixture.

Better flavour – Cannabis grown in soil tends to boast an enhanced flavour and terpene profile, making it a favourite medium among connoisseurs.

Drawbacks of growing cannabis in soil

Slower growth – Cannabis grown in soil grows slower than cannabis grown in other media, especially hydroponics.

Susceptible to Pests and Disease – Because soil is natural and usually minimally-processed, the potential for pests, dormant larvae and disease is increased in comparison with a hydroponic medium.

Uses More Water – Because soil growers tend not to reuse their water, soil actually requires more water than hydroponics systems.

Heavy – Soil tends to be heavy and difficult to move if necessary, making it less than ideal for indoor growers with limited space in their grow room.

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Coco Coir

Coco coir is made from ground-up coconut husks and comes in a variety of formats, from finely ground (“peet” or “pith”) to larger, coarser chunks (“chips” or “croutons”), making it perfect for a variety of systems. Widely reputed for its physical similarity to soil, coco coir is actually more closely related to hydroponic growing media, as it is inert and highly water-retentive. Because it possesses characteristics of both soil and hydroponic media, coco coir has become an industry standard, and with good reason.

Benefits of growing cannabis in coco coir

Aeration – Coco coir’s composition, particularly when mixed into soilless mixes containing perlite or vermiculite, makes for excellent drainage and aeration. This allows plenty of oxygen to reach your plant’s root system, resulting in faster and more abundant growth.

Bug and Disease Resistant – The presence of beneficial bacteria, such as Trichoderma, as well as hormones from the coconut tree, create a growing medium that is resistant to many diseases and pests, particularly those spurred on by overwatering.

pH Neutral – Coco coir’s inert nature gives it a naturally stable pH level, making it a fantastic buffer while simultaneously offering the grower complete control over growing conditions.

Forgiving – Coco coir can be flushed easily and replenished with necessary nutrients, meaning mistakes like over-feeding and nutrient lockout can be remedied relatively painlessly.

Reusable – Because coir can be flushed so easily, it can be returned to its initial, inert state with ease, making it reusable for your next grow.

Drawbacks of growing cannabis in coco coir

Inert – Though advantageous in many ways, coco coir’s pH neutrality makes it susceptible to fluctuations, requiring a grower to maintain continuous observation of pH, EC and PPM levels.

Dries Out Quickly – Coir’s aeration properties also cause it to dry out more rapidly. Growers using coco coir must be aware of their root system’s moisture.

Can Cause Problems in Hydro – Though an excellent hydroponic medium, coco coir (especially pith) can seep into hydroponics reservoirs through nutrient solution runoff, clogging drip lines and pumps.

Cannabis strain grown in soil growing medium

Hydroton Expanded Clay Pebbles

Hydroton expanded clay pebbles (or “pellets”) are an inert soilless medium perfect for many types of hydroponic setups. Expanded clay pebbles work wonderfully in net pots, making them particularly well-suited for deep water culture (DWC), nutrient film technique (NFT), bubbleponics and aeroponics systems. Some growers choose to use expanded clay pebbles as a soil or coco coir amendment, increasing drainage and aeration in their potting mix.

Benefits of growing cannabis in expanded clay pebbles

Faster Growth – Because they are so porous, expanded clay pebbles provide excellent aeration, decreasing the length of the grow cycle.

Reusable – Like coco coir, clay pebbles can be thoroughly washed and reused in future grows.

Pest and Disease Resistant – Bugs tend not to lay eggs in expanded clay pebbles, and the medium’s superior aeration prevents the accumulation of moisture in root zones, helping to curb issues like root rot.

Drawbacks of growing cannabis in expanded clay pebbles

Requires Washing – The clay with which expanded clay pebbles are made releases lots of dust and can easily clog drip lines and emitters; thus, clay pebbles require vigorous washing before use.

pH Fluctuation – Expanded clay pellets must be buffered before use; failure to do so can result in drastic fluctuations in your root system’s pH levels.

Dries Out Quickly – The fantastic aeration provided by clay pebbles can also cause your roots to dry out quickly if left unattended.

Rockwool

Made from superheated volcanic rock, which is then stretched into fibres, Rockwool generally comes in cubes of varying sizes and is widely available. Growers love Rockwool for its versatility, water retention and aeration properties, making it one of the most commonly used substrates on the market.

Benefits of growing cannabis in Rockwool

Aeration – Like clay pebbles and coco coir, Rockwool provides excellent aeration to your plant’s roots, spurring on fast, robust growth.

pH Neutral – After buffering, Rockwool will remain pH neutral, giving the grower complete control over the medium and helping to combat disease and infestation.

Easy to Work With – Rockwool cubes are already cut to varying sizes, with many larger cubes accommodating smaller cubes for simple transplanting.

Drawbacks of growing cannabis in Rockwool

Dries Out Quickly – Like coco or clay pebbles, Rockwool dries out quickly, requiring a watchful eye from the grower.

Requires Buffering – Rockwool has a pH level of roughly 7, meaning it must be buffered down to a pH of 5.5-6.5 before use.

There are benefits and drawbacks to all of the most popular cannabis growing media. Which media will ultimately suit your grow will have to be determined by you. Carefully consider the climate, type of system you will use, lighting conditions and airflow before settling on one, as each medium reacts differently to different environmental factors. Be sure to check out Marijuana Grow Shop’s archive of grow-related resources to learn more about setting up and pulling off a successful cannabis grow today!

Post author
Michael Richey
Michael loves to grow cannabis and write about what he learns along the way. His best friends are his dogs and marijuana.
See more from Michael Richey

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