Seasonal Indoor Cannabis Growing Advice

indoor cannabis growing, growers

Contrary to popular belief, indoor cannabis growing also has its challenges with the changing of the seasons. These challenges occur no matter how well built and insulated growers make their grow room design. As such, the weather and temperature in the outdoors greatly effect these carefully controlled indoor climates. Nonetheless, the industrious cannabis growers can offset these climactic fluctuations. Even more, they can often times harness these seasonal changes to work towards successful horticulture plans and a bountiful harvest.

Here are is some valuable advice on running indoor cannabis growing operations during the wintertime:

CO2 Enrichment

The effectiveness of CO2 enrichment for indoor cannabis growing is dependent upon several factors. These factors include: the infrastructure of the room, the use of air conditioning, lighting logistics, as well as the type of CO2 emission device. It’s important to note, however, that all of these variables interact with fluctuations emanaindoor cannabis growing, growersting from the outdoor climate. Let’s start with warm summer months. In these times, AC units and exhaust fans in have to work overtime to keep grow room temperatures at an ideal state. This happens regardless of CO2 enrichment.

The winter months allow for much more versatility concerning the use of CO2 with indoor gardening. Because, the winter weather plays an essential role in keeping temperatures cool in grow rooms. With the flexibility afforded by winter temperatures, indoor cannabis growers should choose their CO2 enrichment systems in conjunction with their specific needs.

Sealed Rooms

With sealed grow rooms that continue to use AC in the winter months, growers have the option of using the notoriously warm propane CO2 burners. They can do this without overheating their rooms or overworking their AC units. Propane CO2 burners are beneficial largely from a convenience standpoint. To this end, propane tanks can be filled at almost any gas station. Conversely, actual CO2 tanks must be filled at specialty shops.

Traditional Exhaust Setups

Let’s look to the more novice and traditional exhaust-based indoor cannabis cultivation setup. In this case, CO2 enrichment is often not even an option for indoor gardening in the warm summer months. Within this framework, environmental controllers dictate whether the exhaust is pulling air out of the room. Similarly, growers control if the exhaust is off and the CO2 emission device is operational. As such, these environmental controllers are dictated by temperature and humidity levels. Therefore, cooler temperatures allow for more CO2 emission with less use of the exhaust. In either scenario, the winter temperatures of December will allow for a more constant level of high CO2 PPMS in any indoor grow room.


Depending upon outdoor climate, winter weather generally means a higher humidity level for indoor cannabis growing operations. Firstly, many geographies experience far more precipitation outside during the winter months. Secondly, wintertime weather causes temperatures in grow rooms to drop to a certain level relative to the amount of humidity in the air. This dew point in the micro atmosphere can become problematic. This phenomenon occurs as the water vapor in the air (humidity) is released by reaching a cold air temperature threshold. The solidification of water vapor into condensed liquid form is referred to as “dew” in standard climatological thought.

indoor cannabis growing, growers

The formation of dew within a grow room can lead to a number of cultivation problems. Many of these issues can be offset with proper cultivation technology. These indoor cannabis growing issues include both powdery mildew and botrytis. Therefore, the use of a dehumidifier in grow rooms can help counteract potential problems caused by both outdoor precipitation and indoor humidity during the winter. Dehumidifier units often double as air conditioners to be used during the summertime. For growers, purchasing one of these can help offset the cost of purchasing a dehumidifier strictly for the wintertime.


With the influx of cold temperatures during winter, cannabis growers are faced with the challenge of providing consistent environments for their crops.

Ideal indoor garden temperatures should range between 72 and 76 degrees Fahrenheit. This temperature range should be maintained with the lights both on and off. Because, temperature fluctuations of more than 15 degrees Fahrenheit between “day” and “night” can contribute to the aforementioned dew point issues. Furthermore, problems arise if grow rooms reach temperatures below 55 degrees Fahrenheit. Past this threshold, plant growth is retarded and even halted.

To combat temperature fluctuations between day and night in a cannabis grow room, it’s recommended that growers utilize a heating device. Economically savvy growers will look for heating devices that are multi-functional and can be used, in some form, year round. For example, some mini-split AC units can double as heaters in the winter time. This perk allows for the streamlining of the electrical load of a grow room during all seasons.

Spider Mites

During all times of the year, spider mites pose a constant threat for indoor cannabis growing. However, the higher temperatures in grow rooms during the summertime provide an ideal climate for spider mite eggs to hatch and mature quickly. As growers have more options for regulating temperatures in the winter months, they have a far better chance of controlling spider mite populations than in summer. To elaborate, a grow room maintained at 75 degrees Fahrenheit in December provides a climate far less conducive to spider mite growth and reproduction than a room kept at 80 degrees Fahrenheit in July. Therefore, cooler grow room temperatures in winter will work in unison with organic sprays to effectively eradicate these harmful pests.


This article originally appeared in the January 2017 edition of Maximum Yield Magazine.