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Features Cannabis Crops
Growing Points: Prescription for a new crop

July 11, 2014  By Dr. Mohyuddin Mirza

I am sure our readers know about medical marijuana. There has been a lot of coverage in the news media and business magazines.

I am sure our readers know about medical marijuana. There has been a lot of coverage in the news media and business magazines. The continued discussion on the social, legal and legislative aspects of this medicinal plant is intriguing in the sense that once the arguments start, there is no limit to which the two sides will go.

An Alberta councillor had the following to say to Global TV Calgary. “Basically, agriculture is that you plant seeds in the spring and harvest in the fall. We don’t see this as a normal agricultural operation.”


Obviously, in his opinion, greenhouse horticulture is not part of agriculture because he was against its cultivation in the area. He suggested that it should be cultivated in city warehouses, similar to how “factory” manufacturing is done.

On the other hand, some municipalities in North America are encouraging investments in medical marijuana facilities. Some are said to be offering tax incentives.

Then I hear critics say that if marijuana is grown in the soil, it will destroy its agricultural potential. Some people are concerned about the typical odours of marijuana being grown in their area…although we are used to different types of agriculturally related odours!

(Recently, while I was out driving, manure was being spread on fields I was passing. A strong odour was prevalent for several hours in the air I was breathing.)


So what is medicinal marijuana? It is a Cannabis plant with medicinal value.

There are three species commonly known: Cannabis sativa, cannabis indica and Cannabis ruderalis. There are many strains or types mentioned in the marketplace relating them to certain medicinal qualities. They are indica dominant, sativa dominant or pure sativa.

What about medicinal ingredients? THC is the most common ingredient associated with marijuana. THC stands for “tetrahydrocannabinol,” which is one of at least 60 active cannabinoids identified in cannabis. Cannabidiol (CBD) is a major constituent of the plant, accounting for up to 40 per cent of its extract as a non-psychotropic phytocannabinoid. CBD is considered to have a wider scope of medical applications than THC. C. indica produces higher level of CBD compared to THC while C. sativa produces higher level of THC compared to CBD.

About the cannabis plant: It has the same basic processes as other plants, such as photosynthesis, respiration and transpiration, and it produces glucose as the first step of making food.


After making food, it then makes those cannabinoids based on its genetics. Like other plants, it has a vegetative stage, and then a reproductive stage and a generative stage.

Here are a few pointers for growing cannabis after you have learned about the strains you are interested in and have followed the laws of the land. I believe that it is just another horticultural crop with great value that can be of great economic importance for us, in addition to relieving human pain and suffering.

Seed germination is fairly straightforward. On a smaller scale, the seeds can be chitted on a paper towel and directly germinated in rockwool cubes. It germinates well between 20-22 C, and some 80 per cent of the seeds should germinate within 72 hours. Once the roots are visible and two centimetres in length, they can be transplanted into a growing medium.

After transplanting, provide a minimum of 5,000 lux of lights. Many growers have a tendency to keep the lights too close, less than one foot from the seedlings. The leaf temperature could rise very quickly and leaves may not expand fully. Due to excessive transpiration, the seedlings can die off.

Fertilizers 02-Fertilizer
Photos courtesy
Dr. Mohyuddin Mirza

Start fertilizing with half-strength solution, and with an EC of around 1.5 millimhos. The previous two pictures show a young seedling two weeks old, with two true leaves fully emerged (at left) and seedlings four to five weeks old (at right) that are ready for planting into a larger container.



Just a note about fertilizers: I am finding that many growers are using “secret” formulations for vegetative growth, including vitamins (and especially vitamin D). I think we need to understand that cannabis is like any another plant and has similar nutrient requirements. These nutrients can be supplied easily and effectively from regular greenhouse fertilizers. If you want to grow organically, those protocols may be around or need to be developed.

Male plants: If you are growing plants from seeds, then expect to have some male plants. Male plants don’t produce flowers, and will need to be discarded unless seed production is needed.

Male plants produce vegetative “balls” (at left, top image). Below it is a mature male plant.

I have seen so many different types of growing media from soil to soilless, including gravel hydroponics, coir, peat moss and Nutrient Flow Techniques. As long as you know that a growing medium should have good drainage, good air porosity and good water holding capacity, then plants can be managed. Plants are most commonly grown in three-gallon or five-gallon nursery pots.

three gallon  

Plants are being grown in two-gallon containers (top), and in three-gallon containers (above).

Cannabis plants need a full feed with plenty of calcium and magnesium. It needs a pH of leach maintained between 5.8 and 6.2 and an EC adjusted based on light conditions.

My recommendation is to stay around 10,000 lux of light if growing indoors.

If High Pressure Sodium Lights (HPS) are used, then make sure that the light at the plant’s surface is at least 8,000 lux. The EC of the feed has to be adjusted; an E.C. above four millimhos can switch a plant’s direction to being more generative.


Watch for nutritional deficiencies as they can occur frequently. The biggest problem is a deficiency of magnesium. I recommend maintaining a 3:1 ratio of calcium to magnesium from the beginning.

Like tomatoes and cucumbers, magnesium deficiency starts on the lower or recently mature leaves. Veins are green and interveinal areas are light green to begin with and turn yellow later on.


In this series (at left), you can see a magnesium deficiency in the young plant on top. Below it is a mature plant with flowers showing a combination of deficiencies.

Many growers stop fertilizing at this stage of growth. I believe that this is the time when a lot of energy is needed by plants to “ripen” those buds. Fertilizing should be maintained with lower nitrogen and higher potash ratios.

Powdery mildew is very common in these plants, and it can be devastating if infections start early. Paying attention to environmental controls can help a lot. Relative humidity that’s too dry is one big reason for this fungus to grow.

Spider mites can also cause havoc.

At a later date, I will write more on making the plants vegetative or generative by creating stress on the plants. There are many other aspects of growing medical marijuana that are related to the quality of the end product.

We still need more research on proper production protocols and environmental management. I hope that funding agencies will start looking at more projects with medical marijuana. I am sure you also know that you need a licence from Health Canada to grow medical marijuana, and that there are many rules and regulations that must be followed.

Dr. Mohyuddin Mirza is an industry consultant. •

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