There are two types of plants a grower might consider: autoflowering varieties or photoperiod varieties.
Will growing a plant indoors without grow lights leave you with wonky plants? Lower yields? Less potent flower?
“I make zero effort to control the climate of my grow spot. If you’re growing without a light, that plant will be just fine in regular household conditions that are suitable to us humans,” explains Jimmy B Harvests, a YouTube creator that documents his adventures in growing cannabis, along with other fruits and vegetables, at home.
Successfully growing a cannabis plant indoors is all about covering the plant’s basic needs: air, light, temperature, water, and nutrients. So, if you get those things right, your homegrown cannabis plant could provide much more than a fun experiment. And considering that indoor cannabis plants can grow a few feet tall and equally wide, you should anticipate young plants to take up more space by the time they reach maturity.
What to expect when growing weed indoors without lights
Keep it simple to start. When it comes to your setup, “I would challenge people to try doing as little as possible on their first plant and adding in effort or equipment only to solve issues as they arise or to better future plants,” shared Jimmy.
One challenge for growers in wintry climates is the impending chance of their electricity going out during the winter months. Indoor growers rely on electricity to keep plants alive, especially in the winter, so it’s a good idea to prepare ahead of time.
However, in order to get most cannabis plants to start flowering (making buds), you need to give them at least 12 hours of complete darkness every day, which means grow lights need to be off for 12 hours/day. For some growers in a wintry climate, a 12-hour dark period (even during the day) will send the temperature plummeting too low.
Auto-flowering strains let you keep your grow lights on for 24 hours/day, which helps keep plants warm in cool grow areas
However, if you deal with cold temperatures, LEDs are a poor choice. Not only do they produce little heat, but they also make plants less resistant to cold in general. On the flip side, HID grow lights like CMH/LECs and HPS produce a lot of heat to help keep plants warm. HPS in particular also produces a lot of infrared light, which helps raise the internal temperature of leaves to help keep plants warm from the inside out.
When temperatures in the air drop, the amount of water that becomes vapor also decreases. For example, when your air temperature is 41F, this can sustain much more water than temperatures of 60F. However, it isn’t just the amount of moisture in the air that will impact your cannabis grows in the winter; instead, you should consider how winter temperatures may increase the possibility of condensation especially when temperatures drop at night.
Your grow room will need additional heating during the cold, winter months. During the day, your cannabis plants should be exposed to temperatures of 75-86F, while at night it should be somewhere between 64-72F. It’s especially important to keep in mind that the speed of growth, and the quality of your grow, will be seriously affected if nighttime temperatures drop below 61F.
The Bottom Line
Winter tends to be the driest time of the year for many areas, which is why it can be problematic if you’re growing any kind of plant especially cannabis. Winter can mean that air in your grow room becomes too moist, and air brought in from the outside may be extremely dry. Either way, having a humidifier will go a long way. This, and a careful, close watch on your end will help you be on top of humidity levels in order to find that perfect balance.
It’s also important to monitor the ambient humidity of your indoor grow during the winter. Between temperature and humidity, most novice growers tend to underestimate how critical humidity can be during the winter.
Additionally, you should be keeping a close eye on the difference between daytime and nighttime temperatures especially during the first 3 weeks of the flowering phase. If the change in temperature when you go from day to night is far too big, this may result in stretched-out cannabis plants with wide spaces among its internodes. For optimum growing results in the first 3 weeks of flowering, the temperature differences from day to night should be around 3.6-7.2F. For the rest of the growing period, you should be looking at a discrepancy of around 18F when going from night to day.
During winter, closely monitoring your grow is critical to ensuring your plants withstand the cold temperatures. Small things can dampen your efforts, such as leaving a small window open which allows bitter, cold air to come in; having your heating systems break down at night; the presence of mold, and much more.
Lighting, of course, will also play a role here. If you’re already using a lighting setup that gives off a lot of heat, you’re at an advantage because these will already give your plants adequate heat to stay warm enough during the day. But at night, a significant reduction in temperatures overnight may be dangerous particularly after your lights are switched off. To resolve this, just switch your cycles around: see what happens if you leave your lights on overnight to make up for the cooler temperatures, then turn them off at daytime when the temperatures are more consistent and appropriate.