GROW MEDIUM BASICS

Understanding the Foundations for Healthy Plant Development

A grow medium is the substrate where plant roots are anchored. Whether using soil, coco, or pure hydroponics, plants uptake nutrients with the assistance of their grow medium. 


Grow mediums can be narrowed down into three main categories:


  1. Traditional Soil
  2. Soilless (a substrate such as coco or peat moss)
  3. Pure hydroponic system (water as the substrate)


In just about every medium, nutrients need to be added to provide proper nutrition for the plant. Plant roots require oxygen, and plant leaf tissues require the input of carbon dioxide to carry out photosynthesis. However, plants cannot survive on oxygen alone. They need the input of inorganic nutrients, such as calcium or magnesium, to carry out basic functions of life.


Soil: 


Traditional soil can be thought as the most basic understanding of what a plant needs. Soil is abundant and is fairly easy to maintain. It usually contains both organic and inorganic compounds. Though sometimes, soil is inert. This means that supplemental nutrients need to be added. These nutrients become available for uptake during times of watering. 


Plants can naturally react with a soil medium, acting as a buffer. Soil also has a high water retention capacity. This is neither a pro nor a con. It all comes down to being aware of this fact, and watering or feeding the plant at appropriate time intervals. A high water retention capacity could be a downfall if overwatering occurs. 


Soilless: 


A soilless medium behaves similarly to soil, but is composed of different material. Soilless substrates are inert, and require added nutrients. Common examples of soilless mediums are coco or peat moss. 


Coco: some notable properties of coco are that it dries quickly and needs more cal mag (calcium and magnesium). This is especially true during early phases of growth. Though coco tends to be slightly more expensive, it is user friendly and forgiving. Coco also has the ability to hold mycorrhizal colonies. These are fungal colonies that surround root cells and allow for effective nutrient uptake.


Peat Moss: this substrate has a high water retention capacity which can lead to uncontrolled nutrients, flushing and constant balancing. Growers can easily compensate for and manage watering intervals when aware of the high water retention capability. Similarly to coco, peat moss is able to hold beneficial mycorrhizal colonies.


Hydroponics: 


Technically, hydroponics, a specific category of hydroculture, is also considered a soilless system. In this context, pure water acts as the medium. 


A benefit of hydroponic systems is that plants are continuously fed by the nutrient rich water directly. This alleviates some stress, because the plant doesn’t have to go out and search for food. The advantage has the potential to expedite plant growth. Another benefit to hydroponics is not having to purchase a medium such as coco or soil. Considering that this system runs solely on water, a reliable and efficient water source is absolutely crucial. Growers that have any limitations to water access or supportive technology should avoid a hydroponic facility. 


It’s possible that the complexity and risk of hydroponics may outweigh the benefits. Not only is a hydroponic system very expensive to build, but any mistake can be detrimental. In this type of medium, plant cells respond very quickly to a changing environment, leaving little time to notice and fix errors. Mistakes may be as simple as overfeeding, or failed equipment. Immediate changes warrant immediate action. True hydroponic systems tend to be managed by highly experienced growers.


Picking A Medium:


Always back into the advantages you are trying to capture. A lot of this decision comes down to what you as a grower are willing to do in terms of price, maintenance, etc.


Strain also plays a key role when choosing a growing medium. There are some strains that favor certain substrates over others. Some strains want more water, some want less. Ultimately, the medium will depend on the drink rate of the plant. Know your genetics! For example, a cookies would not be good in peat moss because it drinks too slowly. This could lead to overwatering and negative plant stress. You can add perlite to reduce water density or choose a lower capacity medium. 


Economics:


All mediums have advantages and disadvantages. Growing at large scale requires efficiency, for both time and budget. It always comes down to risk management.


As discussed previously, running a true hydroponic system comes with many risks. Growers must decide what that risk is worth, and if the benefits outweigh the potential financial downfalls. For example, let’s say your water chillers go down. The plants would not be provided with water or nutrients for x amount of time. The entire crop could be lost. So the question becomes: is it worth the risk of losing a crop for the potential of quicker yield? 


Unfortunately, there is no cookie cutter method growing cannabis or making these decisions. Each grower has their own knowledge, skill set, and risk threshold. Most decisions are largely preference.


Now, a substrate like coco tends to be less risky. Forgiving mediums buy you buffer time if something goes wrong. Problems are much easier to fix when the plants are responding much slower to the input. Soilless or soil substrates, that are not hydroponic, can be more labor intensive. There are added jobs such as pot cleaning or transferring plants. Does that labor cost outweigh the risk? And what is the price you are willing to pay to be wrong?

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