A Grow Medium, primarily, refers to the medium that you are using to grow your plants in. It can be soil, water, coco coir, compost, vermiculite, perlite, etc. A growing medium is as important for your plant as factors like access to freshwater, oxygen or nutrients. But, without an appropriate medium, your plant may not be able to absorb all the benefits from other essential factors.
With the wide variety of information that is available, selecting an appropriate grow medium can be a fairly overwhelming task. The following article seeks to smoothen this arduous journey by highlighting some of the best grow mediums, their advantages and disadvantages and which one of these mediums can fit in what situations.
The main purpose of any grow medium is to support and enhance plant growth. Therefore, it is important to choose one which works well not just for the plant but for your overall system. Optimum Ph balance, aeration and water retention can change depending on the type of grow medium used and must be taken into consideration before finalizing on the right option. Whether your plant is grown indoors or is cultivated outdoors can also affect the parameters for deciding on the grow medium.
Each grow medium contains its unique qualities and characteristics. Going ahead with one without proper research can be potentially disastrous in the grow room. It can either mean a successful harvest or utter failure. Cannabis is essentially a weed and can grow under diverse conditions. However, for it to thrive and flourish, it requires the right mixture of nutrients from its surroundings. A well selected grow medium can help the plant by helping it absorb the nutrients and minerals and also stay well hydrated and aerated at the same time.
Best Growing Mediums
Grow mediums can be classified into the following three broad categories,
Soil or compost
As this growing medium is natural and easy to use, it is also one of the most popular choices when it comes to growing cannabis.
Soilless mix like Coco or Perlite
Mixtures comprising of inert or non-soil ingredients are known as soilless potting mixtures.
As the name suggests, hydroponics is a method for cultivating plants in water.
Read on to find out more about these grow mediums, their advantages, and disadvantages and what solutions work best for which conditions.
Soil or Compost
Soil and compost are the most popular and the most common grow mediums for growing cannabis as they are naturally occurring, easily available and convenient to use. Both compost and soil contain a healthy amount of micronutrients and macronutrients. As they contain no synthetic substances their water retention capabilities are much better and they can provide the much-needed support for the plant’s initial growth stage. However, it is important to ensure that it is devoid of any weeds or insects. The density in garden soil allows for water and air movement better than any medium. 
Compost is derived after the decomposition of organic matter. Compost can be a combination of leaves, wood waste, grass, animal manures, etc. These are combined with water and left for digestion by microorganisms. While commercial compost is widely available, with the right conditions, compost can be made in your backyard as well. Well-made compost is capable of reaching optimum temperatures that can kill the weed seeds, human pathogens, and plant pathogens. A compost created in your garden is one of the least expensive and highly beneficial grow mediums and can reduce your garbage waste substantially.
Mineral-rich soil and compost also offer the best support for plants and are suitable for both, plant beds and containers. Healthy soil and compost contain the entire spectrum of plant nutrients that are essential for growth, therefore, they provide the ideal structure for the growth of the plant. As they are entirely organic their use does not burden the environment. 
Compost and soil are ideal choices for outdoor growers, however, for indoor growers other grow mediums explored below can be more beneficial. As there are better options available that are as nutritious as soil, indoor growers hardly use soil or compost.
Advantages of Soil and Compost
Following are some of the main advantages of using soil and compost as grow mediums for Cannabis and other plants,
- It is the most widely and naturally occurring of all grow mediums. It is also the most popular for this reason.
- The density provides good aeration and hydration
- For this reason, soil also provides excellent support to your growing plants
- Soil contains essential minerals and nutrients which help sustain plant growth in the initial days.
- Compost, like soil, is rich in nutrients but releases them slowly, often over months or years.
- When added to the soil, compost can improve its structure. For instance, if the soil is sandy, compost can help it retain water and if the medium is clay, then adding compost can help loosen the tight particles.
- Compost neutralizes acid and alkaline soils, thereby, optimizing the pH levels and making sure that a range of nutrients is available for healthier growth of plants.
- Unlike synthetic fertilizers, compost can be made at home in your backyard or garden.
- This organic soil enhancer is no threat to the environment as it does not pollute the waterways.
Disadvantages of using Soil and Compost
In spite of all their advantages, both soil and compost come with certain limitations. Following are some of the common disadvantages of using soil and compost as grow mediums,
- Unlike other grow mediums, the soil is specific to a particular region and therefore can vary in properties from one area to another.
- As the physical and chemical properties of compost are extremely variable it is not a very consistent grow medium and therefore, is not preferred by professional growers.
- Compost can be bought and stored in large quantities as it loses its benefits over time.
- Compost and soil are not as beneficial for indoor plants as they are for outdoor crops.
- Even if it is made in-house, compost is not a very economical grow medium for large scale cultivations. Like soil, every batch of compost can vary in its nutrient composition. For those who are composting in their backyards, the process can take a few iterations before it is perfected.
- Very often, weeds and insects find their way to garden and potting soil and their presence can prove to be fatal for the plant’s growth.
- Odor control can pose itself as a challenge when composting.
Soilless Mix (Especially Coco & Perlite)
Soilless mix is essentially a grow medium that contains various substances but no soil. There are thousands of varieties of soilless mixes available in the market and coco and perlite are the most popular of these. Unlike soil and compost, these mixes are devoid of any diseases, weeds or insects and have consistent pH levels. Due to these qualities, soilless mixes are an ideal option for new growers. Most seasoned or large scale growers combine soilless mixes with other ingredients and prefer creating their blends.
Soilless growing mediums like Coco and Perlite can prove to be an excellent choice for growing cannabis plants. Other types of popular soilless mixes are sphagnum peat moss, vermiculite, and coarse sand.
Coco – Coco, or coco coir, is a natural fiber derived from coconut husks and has been used as a medium to grow plants since the mid-twentieth century. However, it gained popularity only in the 1990s as a viable growing medium. Coco retains water well as it is composed of millions of small micro-sponges that absorb water and are capable of retaining it up to nine times their weight. Unlike regular soil, coco coir is better aerated and plants cultivated in it tend to look bigger and healthier. With lower decomposition rates, it is also one of the most reusable grow mediums.
Perlite – Perlite is derived from volcanic rocks and is usually white. It is mixed with other mediums like peat moss as it does not retain water well on its own. These styrofoam-like balls are added to potting mixtures to increase their mineral content. Perlite has been in use as early as the 3rd century BC. It occurs as a form of volcanic glass that is created by the saturation of volcanic obsidian glass with water over a long period of time.
Advantages of using Soilless Mixes as grow mediums are given below:
- Soilless cultivation is a far more advanced model of cultivation and is usually preferred by large scale growers.
- It is very effective in preventing soil-related diseases and keeps insects at bay.
- As a well-researched product, soilless mixtures provide higher yield and improve the quality of crops.
- It saves not just water but reduces the use of fertilizers as well
- The quality of soilless mixes is consistent and is not affected by the quality of soils of different regions.
- Soilless grow mixes like perlite can be washed and dried for re-use and do not decompose making them useful for years.
- As a porous grow medium, perlite also offers excellent water retention and drainage capabilities. Apart from strengthening root growth, perlite is also a wonderful insulator and protects plants
- Coco coir is lightweight and completely reusable. Its water retention and easy rehydration capabilities put it at an advantage over other grow mediums.
- Grow mediums like coco coir and perlite are inert and sterile and remain free of any bacteria.
- Most soilless mixes are naturally occurring and don’t harm the environment in any adverse way.
- Soilless mixes provide more consistent pH levels.
Let us look at some of the disadvantages of using soilless mixes instead of other grow mediums,
- One major disadvantage of soilless mixes is the cost of investment. The initial and periodic cost of maintaining a soilless mix can be expensive grow medium and for this reason, is not very popular with casual and first-time growers.
- Using this growing medium also requires a certain level of knowledge and technical know-how. Unlike soil or compost, using soilless mediums requires trained personnel.
- Plants react to good as well as poor nutrition much faster in comparison to soil and compost giving the cultivator much lesser time to react.
- Most soilless mixes like coco coir, perlite or peat moss do not retain water for long and tend to dry out.
- Perlite, being an industrial product, can hurt the environment.
- The productivity span of soilless mixes is just 1-2 years after which the nutrients are exhausted and require replacement. This can increase the financial implications of maintaining soilless grow mediums.
- While they are ideal for indoor plants, most soilless mixes are too light and fluffy for outdoor use and tend to erode.
- As coco coir has a high cation exchange rate, it tends to hold onto calcium, iron, and magnesium requiring regular boosting for these nutrients.
As the name suggests, Hydroponics grow mediums are those where the plant is grown primarily in water. The main aim of this method is to allow the roots of the plant to be directly connected with the nutrient-rich water solution. It is recommended to acquire appropriate knowledge before venturing ahead with this grow medium for your cannabis crop.
As there is an absence of soil, most growers use a soilless mix to support their plants and provide them with the right amount of oxygen. Hydroponics, like soilless mixes, is ideal for growing plants indoors. There are broadly 7 types of hydroponic grow mediums, namely, Rockwool, Oasis cubes, Clay pebbles, Coco chips or fiber, Perlite, Vermiculite, and rock.
These hydroponic grow mediums greatly increase the growth rates in the plants. The plants not only mature faster but also, produce more than the plants grown in soil. As nutrients are directly available, plants don’t have to work as hard to absorb them. However, it is important to have enough knowledge to control the solution’s nutrient and pH levels.
DWC, or Deep Water Culture, is the most popular method of hydroponics and is commonly used for growing cannabis plants. This method can support large, nutrient hungry plants and is one of the easiest of all hydroponics grow methods. In this method, there are no spray emitters or drips which tend to clog from time to time. There is, however, a continuous flow of nutrient solution to plants periodically.
Wicking is another easy and probably the cheapest method of hydroponics. Usually done with perlite or vermiculite, wicking can help your plant absorb nutrients at a gradual rate over a while.
In all hydroponic methods, it is recommended to change the nutrient solution in the reservoir every 15 to twenty days.
Some of the top advantages of using Hydroponics for growing cannabis plants are listed below,
- Hydroponics surpass the soil and compost grow mediums in both, quality and yield. The crop matures faster (almost 25%) and produces nearly 30% more than soil-based plants.
- As roots are in direct contact with the nutrient solution, the plants don’t have to work as hard and this makes them focus on the upper growth rather than expansion of roots.
- As the system is enclosed, a hydroponic setup required less water for cultivation. There is a reduced level of evaporation as well in this methodology.
- Hydroponics allows the cultivator to control the grow medium’s variables which may affect the plant’s growth.
- Plants grown in hydroponics have much shorter growing cycles and provides the cultivator with more control over the crop.
- You don’t have to worry about the fertility of the ground. With hydroponics, you can grow anywhere.
- If the grower can ensure a sterile environment, then, hydroponics methodologies don’t require any pesticides.
- Plants can be grown throughout the year, irrespective of the season or the weather.
- As water can be reused, research has found that hydroponics required at least 20% less water than what is used by soil grow mediums.
In spite of its many advantages, Hydroponics also has some crucial negatives. The most common ones are explored below in detail,
- The initial cost of investment and setup is fairly high in comparison to soil and compost
- Due to high cost, most first time growers can’t grow on a large scale.
- Even a medium scale hydroponic system can take a substantial amount to set up.
- It is crucial to maintain optimum water temperature to ensure that your plants thrive. Therefore, it is not ideal for regions with extreme weather conditions.
- The entire system requires to undergo a thorough cleaning and sterilization after every grow cycle.
- Diseases and pests can easily affect the plants grown under this grow medium. Although it may be easier to rectify the situation.
- Most soilless grow mediums are not as readily available.
- Much experimentation is required on the part of the cultivator before deciding on the right methodology of hydroponics and is, therefore, not a very attractive option for first time and small scale growers.
- This methodology also requires more frequent supervision than soil-based mediums.
- Power outages can affect the crops in hydroponic gardens.
- It is easier for waterborne diseases to spread.
With so many options available in the market today, it is extremely likely to be left confused at the end of the day. Therefore, it is important to research every grow medium before finalizing the correct one. While researching, it is also important to take into consideration your capacity to grow and your expectations from the crop. Factors like initial investment capital and space available are as important as your choice of indoor or outdoor cultivation. All of these, and some more, factors can impact the overall growth of your crop.
Seasoned cannabis growers prefer soilless mixtures and hydroponic methods of grow mediums as the plant growth is much faster and the quality is better. It is important to note, that some would have gone through multiple iterations before arriving at the right growth formula.
Therefore, for a novice or casual cannabis cultivators, soil and compost are the most recommended grow mediums. They are not only readily available but are just as rich in nutrients and minerals.
The cannabis plants with grow and thrive so long as their roots have plenty of room to grow and they have enough access to water, oxygen and are grown with optimum nutrient levels. There is no single perfect option available. With this article, we hope to provide a much better understanding of the various grow mediums, their advantages and disadvantages and what environments are best suited for which grow medium. Lastly, whichever method you decide to grow with, it is important to conduct extensive research both on the science behind it and the financial impact that it may have on your budget.