One of the greatest debates among cannabis cultivators is the question of indoor vs. outdoor growing. With the price of post-prohibition marijuana dropping steadily and the global energy market being as volatile as it is, it is the general consensus that greenhouse growing will inevitably become the most economically viable method to mass produce recreational bud
Growing in a greenhouse is great because it allows a grow to harness the natural energy of the sun. The sun’s light heats up the greenhouse, while providing full spectrum lighting, free of charge, all day long. But when winter rears its cold head, the tide shifts, and the concrete walls isolating a warehouse operation suddenly seem pretty warm and cozy.
We put together a few tips for surviving and thriving during the cold season, between see-through walls.
Heating is a Necessity
The most apparent problem during winter is the cold. While cannabis (especially Indica strains) can survive a bit of winter chill, it definitely doesn't thrive in such an environment. This makes heating a necessity. In order to be on the safe side, all heating equipment should be checked prior to the onset of cold conditions. During a harsh winter night, there is no place for down time. Greenhouse growers have already made the choice to aim for cost effectiveness, so in the spirit of efficiency, there are a few steps that can be taken to boost the effectiveness of heating:
- Before winter hits hard, do a complete greenhouse inspection and locate any points where air could leak out. These points are most likely to be found around vents, structural joints, doors, windows, and physical tears in the material. When these are all closed up, the hot air created inside can last much longer.
- When the space is insulated properly, additional layers of insulation can be added, such as specialized bubble wrap or other clear insulating materials to cover the greenhouse walls. Thermal screens can also be used to capture the heat during the night time. Simply let the sun do its thing during the day, and close the thermal screen when the sunlight dwindles. This traps the heat inside, giving a massive head start to nighttime heating.
Keep an Eye on Humidity
One of the perils of growing through the winter is that temperatures can drop suddenly, especially once the sun sets. This can trigger all sorts of problems with your humidity, because the plants in the greenhouse are constantly transpiring, releasing water into the air. When the temperature drops, the relative humidity spikes because the cold air cannot hold as much water. The real peril comes from the fact that, if not dealt with properly, the sudden drop in temperatures and consequent jump in humidity will cause water to condense within the greenhouse. Water droplets will appear nearly everywhere cold, making the entire operation incredibly susceptible to molds and fungi, such as Botrytis – bud rot.
Ventilating in order to reduce humidity, which is the traditional greenhouse method of eliminating humidity, is simply out of the question because of the heat loss it incurs, especially during the night. So the best option to deal with humidity is a dehumidifier.
An additional tip to assist both the dehumidification and heating efforts, is to have proper air circulation in the greenhouse, with the goal of keeping uniform conditions throughout the entire space. If climatic conditions fluctuate between different areas, you may see some plants thriving and others failing Furthermore, diseases such as bud rot only need to take root in one spot to infect the rest of the crops.
At DryGair, we designed our dehumidifiers to help circulate air, providing uniformity in addition to dehumidification, while removing over a gallon of water per kWh. Make sure to note the efficiency of your dehumidification choice (even if it’s not us!), and see what you can get the most value out of.
Supplementing Natural Light
Winter brings shorter days and longer nights with it, but this is not optimal for cannabis. Growers want to provide the optimal conditions for the plant's life stage, and winter’s short days just don’t cut it. Artificial lighting may be needed, and this need grows the further you are from the equator. Efficient lighting is important if want to optimize your electrical usage. Modern LED lights can save much as 40%, compared to CFL, and as much as a whopping 90% when compared to antiquated, incandescent bulbs.
Editor’s Note: HID bulbs can be used to generate heat in addition to their lighting output. HID fixtures also often take up less space in the greenhouse when compared to LEDs, which is important for maximum solar exposure. However, they also have higher electrical demands. There is significant debate in the cannabis community over lights, and we want to make sure to give everyone their credit. 🙂
One simple act to increase the amount of radiation absorbed from the sun is maintaining a clean and clear exterior. Replace old, hazy polyethylene sheets with new clear ones, and clean any snow, water or debris on the exterior of your greenhouse. These efforts can go a long way to increasing your plants' photosynthesis ability and reducing the need for artificial lighting.
Efficiency is the Key to Greenhouse Growing
Growing in a greenhouse requires paying a little extra attention so that even the small details are working for you. A little work goes a long way when it comes to optimizing crop growth in such an environment. But there's no need to worry -- a solid plan can carry you a long way.
We would like to take this opportunity to wish the Growers Network community happy holidays and a plentiful winter, from all of us here at DryGair.
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About the Authors
DryGair’s writers include a team of experienced engineers, agronomists, and economists. They specialize in climate control in closed growing facilities and practical solutions for effective climate management.