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The RQS Blog

What Is The Best Growing Medium For Cannabis?

What is the best medium to use for your cannabis grow operation? Find out the pros and cons of growing cannabis in soil, coco, rockwool, and hydroponics.

25 May 2020

By RQS Editorial Team

Cannabis cultivators can choose from various growing media and techniques to achieve a successful harvest. Do you want to grow in soil, coco, or go with an elaborate hydroponic setup? What are the pros and cons of each, and which one should you choose? Since choosing the right growing medium is an important step on the path to growing great cannabis, we thought we’d provide a guide to make the process easier.

HOW TO CHOOSE THE RIGHT GROWING MEDIUM FOR CANNABIS

A growing medium is where your cannabis plants develop their root system. Many growers keep it simple with pots of soil, but you can also use coco coir, perlite, rockwool, or go for a fully fledged hydroponic setup.

What’s important to know is that there really is no “best” way to grow. Each medium has its pros and cons, though you may prefer one over the other based on your preferences and resources. As long as the roots of your plants can access water, nutrients, and oxygen, they will grow.

Now, let’s take a look at the differences between each growing medium.

SOIL/COMPOST

• Difficulty: Easy
• Cost: Low

Growing in soil is the simplest way to get some nice weed plants going, but don’t think that means soil produces poorer results than other methods. Far from it! Many growers say that soil enriched with high-quality compost grows them the best-tasting weed, even if yields aren’t quite as good as in coco or hydro.

The main advantage of soil is that it is forgiving and beginner-friendly, and you can still crop cannabis of top-notch quality. Soil is also widely available and relatively inexpensive.

ADVANTAGES	DISADVANTAGES
Seeds, a pot, some soil, and some love are all you need. Good for beginners!	Comparatively higher risk of pest infestations, mould, and fungus.
pH fluctuations are typically less severe or problematic.	Plants produce lower yields compared to other growing methods.
Many commercial soils contain enough nutrients for 3–4 weeks of growth.	Plants grow slower, so it can take longer to spot growing problems.
Soil is the method of choice when you want to grow naturally and organically.	Not all soils are optimal for cannabis.
Growing in soil can give you the best-tasting cannabis.	-

ADVANTAGES	DISADVANTAGES
Seeds, a pot, some soil, and some love are all you need. Good for beginners!	Comparatively higher risk of pest infestations, mould, and fungus.
pH fluctuations are typically less severe or problematic.	Plants produce lower yields compared to other growing methods.
Many commercial soils contain enough nutrients for 3–4 weeks of growth.	Plants grow slower, so it can take longer to spot growing problems.
Soil is the method of choice when you want to grow naturally and organically.	Not all soils are optimal for cannabis.
Growing in soil can give you the best-tasting cannabis.	-

COCO/PERLITE

• Difficulty: Medium
• Cost: Low to medium

Growing in a mix of coco and perlite provides the advantages of a hydroponic grow and the ease of a soil grow.

As a coco/perlite mix does not contain any nutrients, you are responsible for giving hydroponic nutrients from the start. The big advantage here is that you have full control, and your plants will grow as fast as in hydro. Downside: Just as with hydroponics, you will have to closely watch your pH levels. It’s also less forgiving of mistakes than soil.

ADVANTAGES	DISADVANTAGES
You can grow big plants with very good yields!	You need to administer nutrients from the start.
You have full control over nutrient and pH levels.	You need to watch pH and EC levels carefully: A small mistake can quickly lead to problems.
No special equipment needed.	Not as widely available as soil. You may need to order coco online.
Coco is a renewable resource.	-
Coco/perlite is (almost) as easy as growing in soil.	-

ADVANTAGES	DISADVANTAGES
You can grow big plants with very good yields!	You need to administer nutrients from the start.
You have full control over nutrient and pH levels.	You need to watch pH and EC levels carefully: A small mistake can quickly lead to problems.
No special equipment needed.	Not as widely available as soil. You may need to order coco online.
Coco is a renewable resource.	-
Coco/perlite is (almost) as easy as growing in soil.	-

ROCKWOOL

• Difficulty: Medium/high
• Cost: Medium

Previously used only in construction, where it experiences widespread use as insulation material, rockwool has become a top medium for horticulture. Just like perlite and coco, it is a so-called “inert” growing medium that doesn’t have any nutrients in it. Rockwool is made from cotton candy-like fibre spun from basalt rock and has excellent moisture-retention abilities. You can find rockwool for growing in a variety of shapes and sizes, from smaller blocks and cubes to large slabs.

Rockwool is most often used in hydroponics. The roots of the plants receive support from the rockwool as drippers provide water and nutrients.

ADVANTAGES	DISADVANTAGES
Rockwool supports a sterile grow with little risk of pests, disease, and infestation.	You need to give nutrients from the start.
Like hydroponics or coco, you have full control over pH and nutrient levels.	You need to watch pH and nutrient levels.
You can germinate cannabis seeds in rockwool cubes. When transplanting, you can just keep the seedling safely in its cube.	You can’t grow organically.
-	You need to soak rockwool in low-pH water before use.
-	Rockwool is not natural and doesn’t biodegrade. Reusing rockwool is not recommended.

ADVANTAGES	DISADVANTAGES
Rockwool supports a sterile grow with little risk of pests, disease, and infestation.	You need to give nutrients from the start.
Like hydroponics or coco, you have full control over pH and nutrient levels.	You need to watch pH and nutrient levels.
You can germinate cannabis seeds in rockwool cubes. When transplanting, you can just keep the seedling safely in its cube.	You can’t grow organically.
-	You need to soak rockwool in low-pH water before use.
-	Rockwool is not natural and doesn’t biodegrade. Reusing rockwool is not recommended.

HYDROPONICS

• Difficulty: Medium/high
• Cost: High

There are various types of hydroponic setups used for growing cannabis. Some systems hold plants in pots filled with a hydroponic growing medium such as clay pebbles, perlite, or rockwool, with drippers dispensing water and nutrients to your cannabis.

You can also find setups that do not use a solid growing medium at all. In these systems, plants are suspended above a tank, with the roots reaching down into the water/nutrient solution. Some systems may use a combination of these, with the plants in a solid medium and the roots suspended in a tank. Simple dripper setups are relatively affordable, while more elaborate systems that make use of pumps and other equipment can be quite expensive.

ADVANTAGES	DISADVANTAGES
Your plants will grow large and fast for maximum yields.	You need to maintain the correct pH and nutrient levels.
You have control over the pH and nutrient levels of your cannabis.	You need to empty your tank and clean your system once in a while.
You don’t need to feed as much (if you have a recirculating system).	You need to give hydroponic nutrients from the start.
Low risk of pests and soil-based diseases.	A hydroponic setup will cost more than some pots and a bag of soil.
-	Your weed may not taste as “natural”.

ADVANTAGES	DISADVANTAGES
Your plants will grow large and fast for maximum yields.	You need to maintain the correct pH and nutrient levels.
You have control over the pH and nutrient levels of your cannabis.	You need to empty your tank and clean your system once in a while.
You don’t need to feed as much (if you have a recirculating system).	You need to give hydroponic nutrients from the start.
Low risk of pests and soil-based diseases.	A hydroponic setup will cost more than some pots and a bag of soil.
-	Your weed may not taste as “natural”.