Growing Cannabis plants is a sweet science that is easy to get right, however can also easily go wrong. What growing medium you are using, can play a huge role in the quality of root production, root health, vigor, nutrient uptake and overall vitality. In this article, we explain what to consider when choosing the best growing medium for Cannabis, allowing you to produce the healthiest and most vibrant crops possible!
What to check for when buying a growing medium for Cannabis
If you are new to growing Cannabis indoor or outdoors, then you may not consider the different elements which make up a top quality medium. There are important factors to consider such as the short term and long term nutrients being supplied to the plants, how many air pockets are present around the root hairs, the ability to hold water as well as drying out time.
Growing Cannabis plants requires providing a balanced amount of nutrients to the plants, during the different stages from seedling, vegetative, pre-flowering and full flower production. Normally, a grower will choose to work with liquid nutrients that usually come with a feeding chart or basic direction to feel 1-5 ml per liter depending on the maturity of the plants.
Complete soils will contain enough nutrients to last the duration of a full grow, however it is recommended to complement with liquid nutrients for the best results. Cannabis plants will require Nitrogen, Potassium, Phosphorus as well as trace elements to maintain health and happiness.
Top Tip: As a beginner growing Cannabis plants for the first time, the best option is usually an organic complete soil, with liquid nutrients and an easy-to-read feeding chart. Many brands offer a complete soil designed to supply enough food from planting the seeds until harvest.
The aeration quality
Oxygen is a key player in plant growth, and especially when it comes to producing a well established and prolific root zone. Air pockets within the growing medium will encourage roots to grow into small spaces and tiny crevices in search of moisture, nutrients and microbes.
How much air is present within the pots you are growing in, will also affect how well the pots can drain and dry out. When growing Cannabis plants, a growing medium that lacks air pockets will feel very heavy once watered and will also take the longest amount of time to dry out between feeding.
Top Tip: Cheap and low quality soils will have poor drainage and will often be the least favorable when it comes to a soft, airy and oxygen rich growing medium. Adding coco, perlite and hydroton can significantly increase aeration and drainage quality.
What about water retention and drainage?
How much water your growing medium is able to pass through or hold on to, will have a direct effect on the drying out time between feeding, as well as oxygen levels present around the root hairs. When growing Cannabis, one way to find out is to see how long it takes for a liter of water to pass through a 10 liter pot. If there are signs of no water free flowing out the bottom after 30–60 seconds, then there is a good chance your growing medium has poor aeration and drainage.
If you imagine a 10 liter pot filled with a heavy and cheap soil that takes 2–3 days to dry out, compared to a 10 liter pot filled with 50% soil and 50% perlite, which is ready for another feeding within 24 hours, you can clearly see the long term effects of a good to bad ratio of water retention, wicking ability and drainage.
Top Tip: A heavy growing medium, especially once overwatered, can put high amounts of pressure and weight on the roots, and will reduce the amount of oxygen present, potentially resulting in root rot, anaerobic bacteria or other harmful pathogens. Only water once the growing medium is totally dry and can be lifted with the least amount of weight.
Drying out time between feeding
How quickly your growing medium can fully dry out before requiring another feeding, will be determined by a wide number of factors such as light intensity, pot size, temperature and humidity levels, air flow and the overall quality of the soill. The more frequently Cannabis plants can receive a nutrient solution, the bigger it can grow and, as a result, produce the biggest yields and the most terpene rich buds and extracts.
Top Tip: The easiest way to add more air pockets and substrates to the growing medium is to use perlite. A very cheap and easy to use additive that will reduce the final weight of your pots when fully saturated and will reduce the risk of overwatering for a beginner grower. A 50/50 or 40/60 ratio of perlite to coco or soil works well.
The Different mediums for growing Cannabis plants
Soil / Compost - The most practical way to get your career started as a grower, and usually the easiest to source locally. There are many top quality light and complete soils that can be purchased on line, especially designed for growing Cannabis plants. When it comes to buying soil, it is always best to pay the extra and go with the most reputable brands.
Coco - Coco contains no nutrients and is classed as an inert medium. Used as a buffering agent for hydroponic growing, coco is also an excellent additive to combine with a complete soil in order to achieve a light, spongy and oxygen rich growing medium.
Perlite - a small sized, lightweight weight material created from amorphous volcanic glass. Using perlite can help stretch the growing medium and increase the amount of oxygen present. Those who use coco, often prefer a 50/50 ratio of perlite to allow for the ideal dripper set up for drain to waste or recirculating systems.
Vermiculite - A flaky natural occurring mineral that has a shiny characteristic and is able to retain a lot of water. Used in growing mediums to hold onto moisture often used for cloning propagators.
Growing Cannabis plants successfully requires the best growing medium possible, nutrients, lighting, and overall care and attention. The ripple effect of a low quality soil or custom blend can often have consequences further down the line. The most common mistake made by beginners who use a cheaper alternative soil is overwatering their pots, due to poor aeration. Drainage, wicking ability, water retention and the amount of air pockets all play a big role in the overall quality of the roots, meaning they have a significant impact on resin, terpene and flower production. Good luck finding out which custom growing medium works best for you!