Which Growing Medium Is Best & Why

Which Growing Medium Is Best & Why

There are many ways to grow Cannabis ranging from indoors, outdoors, hydroponically and using organic methods. Often times growers will start out with organics and never really venture into the world of automated systems. In the blog post BioTabs breaks-down the different types of growing mediums, the difference between hydroponics and organics as well as, top tips about what to consider before planning your next grow project.

Organics and Hydroponics

When growing Cannabis with organics, the grower can relax knowing that all of the essential elements the plant requires, are provided within the growing medium. Naturally there will be a 72 hour buffering zone, before nutrients are slowly broken down to a format that the roots can easily absorb.

Hydroponics on the other hand, depends on the liquid nutrient solution to be delivered via water. There is no buffering process and even the molecular structure of chelates in the food are designed to be absorbed differently, than with organics. This means that the grower must be vigilant of pH and E.C before and after feeds.

The Different Substrates Available


Usually available to buy as a complete soil, containing all the essential nutrients and trace elements. The most basic version of organics is to grow using a complete soil that only needs water adding. Within the soil should be beneficial bacteria and fungi that will allow nutrient uptake to occur faster and more efficiently.

Top Tip: Beware of cheaper soils that can be bought locally, as these often lack the mineral content a Cannabis plant will require. The aeration and drainage may also be inadequate and will only cause problems later on.

Small Cannabis Plant Grown In Soil

Small Cannabis Plant Grown In Soil

Growing Cannabis in Coco Coir

Growing Cannabis In Coco Coir


Made of coconut husks, coco has excellent water and air retention and is very popular amongst growers using dripper systems. Roots seem to excel when grown in coco thanks to the light weight structure and the abundance of air pockets. Often combined with a 50/50 mix of perlite to promote more dry back periods, coco is a very popular choice for hydroponics and custom soil mixes.

Top Tip: Coco has an excellent water retention capabilities, however adding perlite will allow the number of times the medium experiences wet to dry periods to increase. Coco and perlite can both be reused after a full growth cycle, using enzymes.

Worm Castings

Produced by living worms and packed full of beneficial microorganisms, worm castings are fantastic for plant health. A slow release of primary and trace elements will allow the garden to remain green and lush, plus these are often a good cure for a nutrient deficiency. Growers will usually mix worm castings together with coco to enjoy a fine blend of nutrition and easy to work with substrate.

Top Tip: Invest in a worm bin that you can have at home, to recycle your organic food waste and garden waste. These are also inexpensive and a brilliant way to introduce children into the world of true life organics.

Growing Cannabis with Worm Castings

Growing Cannabis With Worm Castings

Rooting Cannabis Clones in Perlite

Rooting Cannabis Clones In Perlite


A very cheap substrate that is designed to increase air pockets, and maintain the wet and dry balance between feeds. Growing in hydro with just perlite can be challenging as it is so lightweight and has a very loose and airy nature. The best way to use perlite to improve the aeration of your pots is mixing 30-50 percent directly with your soil or coco blend.

Top Tip: Whenever opening a bag of perlite, it is best to soak the perlite though to eliminate any dry dust. Breathing in the dust is harmful to our lungs, so if you are working with large amounts of perlite, make sure you are wearing a mask or have sprayed the perlite with water or a mild nutrient solution.

Diatomaceous Earth

A rich form of silica as well as trace elements, diatomaceous earth is a sedimentary rock . It has beneficial properties for killing pests and due to its low density structure, can be used in both organics and hydroponics as a bulky stone medium. It is possible to buy diatomaceous earth as a fine white powder that can be used, as an application for top dressing.

Top Tip: One of the best insect killers on the market and extremely versatile in its application. The high amount of silica and the abrasive format, causes problems for pests that come into direct contact with the rock or powder substrate.

Using Diatomaceous Earth when Growing Cannabis

Diatomaceous Earth For Growing Cannabis

Hydroton Clay Pellets for Growing Cannabis

Hydroton Clay Pellets Used For Growing Cannabis


Expanded clay pebbles are an interesting substrate, as they have the ability to dry out quickly, yet hold nutrients within its structure. When used in dripper systems, Hydroton will ensure that there is a high amount of oxygen around the roots, and in some cases drip lines can be left on for 24 hours with no issues of over watering. Hydroton can also be reused once washed correctly and cleaned of old roots.

Top Tip: Make sure that you wash the bag of hydroton clay balls thoroughly before adding them to pots. You will know when all of the dusty sediment has washed away, when the runoff is clear. If hydroton is not washed sufficiently, pumps and air stones will become affected.


One great thing about rockwool is that it has the ability to hold 18 times as much water when wet. This staggering amount allows plants to stay wet without the need to feed again. Of course when growing with hydroponics and using a rockwool cubes that is 4 or 6 inches in size, the dry back period will increase over the duration of the grow. Adding a rockwool slab underneath will promote roots to grow down and into the slab increasing root mass further.

Top Tip:Roots seek out available air pockets, meaning the micro-fibrous structure has plenty of air placement. Avoid over watering with rockwool cubes by checking how saturated the grow cube is before drip lines feed again. Waterlogged roots will struggle to expand and search out new territory.

Rockwool Root Zone for Cannabis Growers

Rockwool Root Zone For Cannabis Growers

Growing With Hydroponic Liquid Nutrients

The art of hydroponics is to grow using only water and an inert growing medium. Basically this means that there is no nutritional value needed from the chosen substrate. Hydroponic nutrients are created to allow the transportation and uptake through a nutrient solution, take place much quicker than with organics. Below are different versions of hydroponic setups that rely on an inert medium for the roots to grow in.

  • Recirculating top dripper system - Hydroton clay balls
  • Recirculating top dripper system - 100% Coco
  • Recirculating top dripper system - 50% Coco and 50% Perlite
  • Recirculating top dripper system - Rockwool cubes on slabs
  • Deep water culture - Hydroton clay balls
  • Recirculating Deep water culture - Hydroton clay balls
  • Nutrient Film Technique - Rockwool cubes on a rooting mat

Organic Hard Foods and Liquids

Blending together all of the relevant organic substrates to create the optimum environment, for both the roots and beneficial organisms will certainly pay off in the long run. As long as the balance is right, adding only water should keeps everything happy and healthy. Growing Cannabis in soil has its advantages, however if you wish to supercharge your custom organic blend, then adding the list below will take your plants to a whole other level.

  • BACTREX - Beneficial for the root system and contains Trichoderma genus mould .
  • MYCOTREX - Blend of 9 species of Endo Mycorrhiza spores.
  • STARTREX - High probiotic bacteria content, containing Silicon (Si) & Fulvic acid.
  • SILICIUM FLASH - Silicon, Nitrogen, Phosphorus & Potassium.
  • PK BOOSTER COMPOST TEA - A mixture of extremely concentrated organic compost.
  • ORGATREX - A biological plant drink created for to feed the beneficial organisms present.

So Which One Is Best For Me?

Once you have a better understanding of the properties of all the various substrates at your disposal, it will allow you to customise the water holding capacity, amount of air pockets, the rate of wet to dry periods, an increase in feeding times and water management, as well as provide the relevant supplementation the plants require at the different stages of their life cycle.

Commercial growers who are required to meet targets will usually grow hydroponically, as the yields are far greater. However, there are many advantages associated with growing organically. Finding the ultimate balance of organic and inert substrates, combined with plant training and experience will allow you to grow the very best plants possible with an enormous root zone!

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