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Scheduling Matters When It Comes To Growing Cannabis

It is definitely an understatement to say that cannabis production and processing is on the rise in Canada. Alongside this increased interest comes the development and dissemination of many myths surrounding its cultivation. (Mainly borne out of people thinking they have secret recipes to grow bigger buds with strong THC, CBD and turpentine contents.)

November 2, 2017  By Dr. Mohyuddin Mirza

Picture Picture illustrates four-week-old seedlings of cannabis sativa. A good example of how vegetative plants should look like. Good green colour It is definitely an understatement to say that cannabis production and processing is on the rise in Canada.

The simple fact is that cannabis is a plant like other plants and it works on the same principles of photosynthesis, respiration, transpiration, assimilates and translocation to various parts of plants. It responds to temperature, relative humidity, carbon dioxide and other factors in the same way as other greenhouse crops and it is susceptible to diseases and insects the same way as other crops. The big difference between cannabis is that it is treated like we are manufacturing pharmaceuticals in a greenhouse or indoors.

Science Lesson
Cannabis sativa and cannabis indica are the two most commonly used species along with cannabis ruderalis. Not to mention there are several other strains or clones being grown in the market place too. I remember that under older regulations, growers were issued permits for a certain number of plants, so each and every plant was cared for in such a way that a lot of spacing was provided and multiple pinching were done. Thus, the plants set buds on the upper part of the plants. When it comes to cultivating cannabis, here are a few pointers to keep in mind when scheduling your grow:

  • Seed germination requires a temperature of around 20-25°C in the growing medium and they germinate in three to five days;
  • All the seed may not germinate at the same time. Remove from germination area once 60 per cent of the seeds have germinated or sprouted;
  • The cotyledon leaves will look different than the true leaves;
  • 16-18 hours of light will be needed. Avoid very high light levels at seedling stage. If the lights are fixed then a shade cloth can be used to reduce the light intensity;
  • From the start, focus on the use of biological disease and insect control products as registered by Health Canada;
  • Use of unregistered products must be avoided at any costs. Take every step to avoid accidental contamination from water or air;
  • It is recommended to thoroughly study the current products registered by Health Canada. How the biologicals work is very important? For example, certain products of spores of beneficial microorganisms need high humidity to germinate and initiate infection of insects. Also, be aware if the use of these registered products is going to affect your Integrated Pest Management Program;
  • Focus on managing plant health right from the start; root zone health is most critical;
  • Don’t go by fixed number of days the plants should stay in veg mode. For planning purposes many growers assign number of days in veg mode or veg room, instead of looking at the condition of plants. Basically, we want plants with good, strong branches, proper leaf expansion and no diseases or insect pressure. If veg plants go into bud room with powdery mildew, thrips or spider mites, then it will be difficult to control them;
  • Understanding nutrients and their management for cannabis is just as important as with any other crop. PH and Electrical Conductivity (E.C.) are two important values that growers must know in depth. PH must be monitored on a daily basis both for the feed solution and leach coming out of the growing medium. It should be remembered that pH in the root zone will change due to alkalinity of water, fertilizers being acidic or alkaline and the stage of growth of cannabis plant. When lots of roots are produced like in veg state, the pH will have a tendency to go towards alkaline side. If pH surpasses the 6.5 mark then expect iron chlorosis in the young growth.
  • Managing E.C. is also very important. I have seen E.C. values over 5.0 mS in the root zone, which will cause the new growth to be very dark green or almost blue-ish in colour. Leaf size will be smaller too.

Currently, most indoor production of cannabis is in soilless growing media, including peat based and coir or coir based. Each growing medium has its advantages and benefits and growers must understand that. Go for growing media with medium porosity and good drainage when put into containers. If coir is used then make sure that it is tripled washed with good quality water and E.C. is below 2.0 mS. Similarly, make sure that there is enough dolomite lime is added to counter any acidic pH coming from peat moss.

Remember, growing cannabis is a science so ensure you have an analysis of the growing medium. This starts by checking if there is enough nutrient charge to begin with, and adopting irrigation and fertigation practices based on the characteristics of the growing media, including drainage, cation exchange capacity, percentage of organic matter, air porosity and water holding capacity.


Dr. Mohyuddin Mirza is an industry consultant who can be reached at Drmirzaconsultants@

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