Temperature And Humidity Control
Temperature and humidity control measures can become one of the more expensive investments when growing cannabis plants indoors. Although the South African climate is generally pretty good for growing cannabis outdoors in summer, growing year round indoors can present a host of challenges if your growing environment is not set up correctly.
Temperature:
All grow lights emit heat in one way or another. The latest LEDs on the market might emit far less heat than conventional HPS or HID lighting, but nonetheless they still produce heat and all heat can get trapped and build up. Unless you extract or get rid of the hot air in the grow room by replacing it with fresh air, your lights will significantly raise the temperature inside a sealed room.
An extraction fan is needed to get rid of the hot air in your grow room and to provide fresh air that will be drawn in from the negative pressure it creates. An extraction fan essentially only provides air movement and heat extraction, but it can not physically lower the temperature below that of the surrounding rooms air levels. Make sure you extract and release your hot air in such a way that it does not circulate through your grow area a second time as this will also cause heat to build up.
Too Hot:
In most parts of SA, there aren’t too many days in a year where the temperatures reach over 34°C consistently, and since most of our strains are pretty hardy and heat resistant you should not run into heat stress problems growing outdoors. For indoor growers an airconditioned room is not really feasible in the long run so rather make sure your room is well ventilated or switch off your lights during the day if things get too hot. Constant temperatures over 34°C generally cause heat stress, but as long as you have sufficient airflow and water, your plants should be OK if it’s only that hot for a few days here or there. For outside temperatures regularly above 30°C, you may want to invest in some shade nets for your plants.
Too Cold:
Cold temperatures threaten outdoor growers far more than indoor growers. Cannabis are hardy plants that will only die in constant temperatures of less than 10C, but their growth and yield will be severely limited if you grow in temperatures less than 18C.
To warm things up indoor growers you can simply switch off the extraction fans, add a heater, or switch the lighting cycle so that it’s on during the coldest parts of the night, and off during the hottest parts of the day. Outdoor growers growing in the heart of winter will have a difficult time in certain regions of our country if they do not bring the plants indoors at night and during heavy storms.
Humidity:
Humidity is something that can only be controlled indoors or in a greenhouse setup. In most parts of South Africa the humidity is not too bad for growing cannabis all year round, as long as your growing environment is not overgrown and you have sufficient ventilation you should not run into any serious humidity related issues.
Raising the relative humidity inside a grow room is not too difficult and hitting that sweet spot during the various growth phases obviously boosts your growth rate, but lowering or having full control over your humidity comes at a pretty high cost and for the average home grower it might be too costly to invest in something like a dehumidifier for full control.
White Powdery Mildew and Bud rot are some of the fatal consequences one can run into when the humidity is constantly too high, but as long as you take preventative measures and you have plenty of air flow both inside your grow room and through the plant itself, you’re likely to be just fine.
To raise the relative humidity:
We always recommend putting a see-through plastic cup over any small seedlings or clones that require higher humidity levels. If the humidity gets too high or you want to slowly introduce your plant to the normal humidity outside then you can remove the cup intermittently letting in more fresh air. Once your plant gets too big for a cup and you can place shallow open trays of water around your grow room or switch off your extraction fans in order to raise the humidity inside your grow room. Be very cautious not to over do it or you will attract mold or pest problems.
Ideal Growing Conditions for Autoflowers
Growing Autos from sprout to harvest only takes about 10 weeks in total, so having the ideal growing conditions is key to your overall growth speed, plant size and thus final yield.
Our autoflowering cannabis plants are easier to grow than regular cannabis because they can withstand a greater range of environmental conditions outside of the ideal. They can be grown indoors or outdoors right throughout the year in most parts of South Africa and do not require a controlled lighting schedule to initiate flowering.
Temperature:
- Week 0 – 2 | 24º C
- Week 2 – 4 | 26º C
- Week 4 – 8 | 24º C
- Week 6 – 10 | 22º C
Humidity:
- Week 0 – 2 | 70%
- Week 2 – 4 | 60%
- Week 4 – 8 | 55%
- Week 8 – 10 | 45%
Lighting:
- Week 0 – 4 | 22 – 24 hours | Blue dominant
- Week 4 – 10 | 20 hours | Red dominant
Conclusion:
The above conditions are merely a guide to achieve optimum results. In the real world these conditions may be difficult to achieve without additional equipment. Temperature is one of the most important factors, but deviating from these conditions by a few degrees will not kill your plant, it will only slow your growth. Planting your plant at the right time of year or location can go a long way toward success. If you are growing outdoors and it is freezing cold or storming outside, it is advised to bring your plant inside. Wind speeds of 25km/h or more can be harmful to your plant. Temperatures under 18C or over 34C will severely stress your plant if it persists. Humidity is out of your control in most cases, but in South Africa it is stable enough not to harm your plant , just ensure proper airflow at all times.
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