What is a growing medium?
A growing medium is what you use to grow your cannabis in, such as soil, pebbles, coco coir, water, rockwool, or anything else that you use to house your growing cannabis roots.
It is vital that you use a suitable growing medium because this directly impacts the health of your plant’s roots. Different growing mediums sometimes require different set-ups, for example, a basic soil medium will just require a pot and to be fed a couple of times per day, whereas hydroponics requires a more frequent supply of water and nutrients.
What is the best growing medium for cannabis?
There are three most popular types of cannabis growing mediums: soil or compost, soilless mixes, or hydroponics. Cannabis plants can thrive in any of these growing mediums, providing the chosen medium consistently supplies the plants roots with access to water, oxygen, and nutrients.
On that note, the best growing medium for cannabis can be made up of any components as long as they meet these requirements:
- have texture that allows good drainage and aeration but also retains water well;
- have pH values close to 6; and
- have enough nutrients to feed the plant up to the flowering phase.
Soil and compost
Soil and compost are the two most common mediums to use for growing cannabis, because they are easy to use, natural and readily available to almost everyone. Many beginners often make the mistake of assuming they can just use some soil from their backyard to grow cannabis in. In most circumstances this will work however there is a little more to it than that.
What makes a good soil or compost for growing cannabis?
I know that I have mentioned this repeatedly, but young cannabis plants are delicate, if you want them to thrive you must take proper care of them while they are growing. If your soil is too compact (a common issue with clayey soils) the plant roots will struggle to grow. A good soil should be relatively loose and airy so that the roots can easily grow.
Soil mixes with added conditioners like perlite are the best to use, because not only do they allow roots to grow, but they also create air pockets which increases oxygen intake and assists with drainage.
Nutrients are vital for optimum growth and all round plant health. Different types of soil contain varying levels of nutrients. Amended or composted living soils generally contain more nutrients aiding growth, particularly in a plants early life before you begin to add additional nutrients.
Amended and composted soils, also known as living soils, contain micro-organisms that live in the soil. This replicates soil that is found in nature closely and provides a plant with a healthy balance of the right nutrients. Nowadays it is easy to find good living soil that comes already pH balanced and containing all of the nutrients required for cannabis to flourish.
Soilless growing mixes
Soilless growing mixes are usually comprised of non-soil natural materials such as coco coir, peat moss, perlite and vermiculite mixed. They usually make a great medium to grow cannabis in because they are specifically produced to provide optimum health for your plants.
The growing method itself is very similar to growing in soil, with the main difference being that there is little or no nutrients in soilless mixes. Because of this the nutrients need to be added to the water when you are feeding them.
Benefits to soilless mixes
- Because you are adding nutrients to the water when you feed your plants, they tend to grow much faster and yields are generally bigger.
- There is less chance of issues with pests.
- There is less risk of overwatering.
The most common mixtures now contain mostly coco coir mixed with 20-30% perlite.
Coco coir is a natural by-product of coconuts. It is made by tearing the fibres off the outer coconut shell where it is processed and added to soilless mixes.
Perlite is made from natural volcanic glass, it is then heated to 871 C. where it rapidly expands and pops to become the incredibly lightweight and airy material that is added to soilless mixes.
My personal favourite soilless growing mix that has worked wonders for me is Dakines 420 Coco Coir, perlite and domolite mix. It comes ready pH balanced and provides the perfect airiness for a substrate to grow cannabis.
Hydroponics is a form of growing cannabis whereby the roots are suspended in water with a constant cycle of nutrient enriched water being pumped around. There are various types of hydroponics, but the most commonly used method is Deep Water Culture (DWC). DWC is the only hydroponics growing technique that can comfortably support large plants, if big yields are what you want then DWC is the way to go.
DWC works by suspending the roots in a reservoir or water and nutrients and using an air pump to feed oxygen bubbles into the reservoir. You would usually use something like clay pebbles as the substrate that would house the plant, the plant pot then has small holes that allow the roots to grow through into the reservoir below. A pump system would then pump the water around into the pot which then drains back into the reservoir and goes around in a constant cycle.
With extra oxygen in the roots:
- Plants grow bigger in less time.
- Plants absorb water and nutrients quicker.
- Root diseases have less chance of surviving.
- The water stays fresh.
Other less common methods of hydroponics growing include aquaponics where the roots are suspended in a fish tank and aeroponics where the roots are suspended in misted air. Neither of these are the best methods for large yields because it can be challenging to support larger plants.
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Rockwool is a material that was created for the construction industry and is used to insulate buildings. It has become a very popular growing medium in horticulture and is one of the most common mediums to germinate and grow cannabis with.
Rockwool is an inert medium, meaning it does not naturally contain any nutrients. It is a fibrous material that is similar in texture to a harsh cotton wool. They are usually sold in small cubes that are used for germination; however they can also be purchased in large slabs.
Rockwool is most used with hydroponics growing whereby the rockwool is used to support the plant with a constant feed of nutrients dripping through.