Contrary to popular belief, indoor gardeners face challenges with the changing of the seasons. This is because, no matter how well-built and insulated a growroom is, the weather, temperature, and humidity in the outdoors greatly affect carefully controlled indoor climates. However, the industrious indoor cultivator knows how to offset these climactic fluctuations and harness the changes to achieve a bountiful harvest. Now that December has arrived, there are several steps growers can take to overcome winter weather.
The effectiveness of CO2 enrichment in a growroom is significantly dependent upon several factors, including the infrastructure of the room, the use of air conditioning, lighting logistics, and the type of CO2 emission device being used. It’s important to note, however, that all of these variables interact with fluctuations emanating from the outdoor climate. During the warm summer months, air conditioning units in sealed rooms and exhaust fans in traditional rooms have to work overtime to keep the temperature at an ideal state, regardless of CO2 enrichment. The winter months allow for much more versatility concerning the use of CO2, as winter weather plays an essential role in keeping temperatures cool in growrooms.
With the flexibility afforded by winter temperatures, indoor gardeners should choose their CO2 enrichment systems in conjunction with their specific needs. With sealed growrooms that continue to use air conditioning in the winter months, cultivators have the option of using notoriously warm propane CO2 burners without overheating their rooms or overworking their air conditioning units. Propane CO2 burners are beneficial largely from a convenience standpoint; propane tanks can be filled at almost any gas station, whereas CO2 tanks must be filled at specialty shops. On another note, in the more novice and traditional exhaust-based growroom set-up, CO2 enrichment is often not even an option in the warm summer months. Within this framework, environmental controllers dictate whether the exhaust is pulling air out of the room, or the exhaust is off and the CO2 emission device is operational. As these environmental controllers are dictated by temperature and humidity levels, cooler temperatures allow for more CO2 emission with less use of the exhaust. In either scenario, winter temperatures allow for a more constant level of high CO2 in any indoor growroom.
Depending upon the outdoor climate of the operation in question, winter weather generally means a higher humidity level in growrooms for a couple of reasons. First, many geographies have far more precipitation outside during the winter months. Second, as the outdoor climate causes temperatures in growrooms to drop to a certain level relative to the amount of humidity in the air, the dew point in the microatmosphere 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 lexicon. The formation of dew within a growroom can lead to a number of cultivation problems, including both powdery mildew and botrytis. Therefore, the use of a dehumidifier in growrooms can help counteract potential problems caused by both outdoor precipitation and indoor humidity/dew point during the winter months. To help offset the cost of purchasing a dehumidifier strictly for the winter months, units often double as air conditioners to be used during the summertime.
With the influx of cold temperatures during the wintertime, indoor gardeners are faced with the challenge of providing consistent environments for their crops. Ideal indoor garden temperatures should range between 72 and 76°F, and this temperature range should be maintained with the lights both on and off. This is because temperature fluctuations of more than 15°F between “day” and “night” can contribute to the dew issues mentioned earlier. Furthermore, if growrooms reach temperatures below 55°F, plant growth is retarded and even halted. To combat temperature fluctuations between day and night in a growroom, it’s recommended that cultivators utilize a heating device. Economically savvy growers will look for heating devices that are multifunctional and can be used, in some form, throughout the year. For example, some mini-split air conditioning units can double as heaters in the wintertime, allowing for the streamlining of the electrical load of a growroom during all seasons.
During all times of the year, spider mites pose a constant threat to the health of any indoor garden. However, the higher temperatures in growrooms during the summertime provide an ideal climate for spider mite eggs to hatch and mature quickly. As indoor gardeners have more options for regulating temperatures in the winter months, they have a far better chance of controlling spider mite populations than in summer. A growroom maintained at 75°F in December provides a climate far less conducive to spider mite growth and reproduction than a room kept at 80°F in July, studies show. Therefore, slightly cooler growroom temperatures in winter will work in unison with organic sprays to effectively eradicate these harmful pests.