Lighting Needs of Cannabis Plants

Which light schedule is the best for auto-flowers?

Which light schedule is the best for auto-flowers?

Autoflowering seeds are arguably the best thing ever happened to the growing community, aside from the trend for legalization. The introduction of this innovation essentially reduced the entry threshold for new growers to the absolute minimum. That is due to the fact that autoflowers require  significantly less work and even forgive some rookie mistakes. 

It is kind of an automatic transmission in the world of Cannabis. Those seeds will start blooming after 6-8 weeks regardless of the lighting mode. Whilst with classic Cannabis seeds you would need to activate the blooming phase by adjusting the light schedule. However, that doesn’t mean that the lighting factor doesn’t need any attention, as it directly affects the potential yield and bud’s potency.

LED lamps are the best due to their power and energy efficiency

Even though it is still possible to achieve a decent result without putting extra effort into regulating the light cycle. The biggest and highest-quality harvests can only be achieved by setting an optimal schedule. Here 3 different but proven methods come into play. Each has some pros and cons. I would recommend you keep an eye on your plant and check how it reacts to various modes, conscious experimenting is always welcomed! 

18\6 Light Schedule

A 18\6 light cycle means that the plant is exposed to the light for 18 hours and then rests in the dark for 6 hours. It is the most common method mainly due to how well it supplements the short vegetative and flowering stages of auto-flowering plants. A lot of growers confirm that this mode results in healthy-looking plants with amazing yields. In order to set the schedule up, you would need to buy a socket timer that automatically turns the light on and off at the right time. You can find one in every well-equipped garden shop.

24-hours Light Schedule

Twenty four hours long light cycle is often used with the hope to maximize the yield and potency of buds. The logic seems to be straightforward, more light equals more nutrients that get generated via photosynthesis and therefore higher yields. However, many argue that such techniques may do more harm than good. The plants require at least some time to recover and process the nutrients just like humans. 

Therefore most of the growers go for the classic 18\6 cycle, which offers substantial light exposure as well as some time to rest during the dark period. The only benefit of a 24 hours cycle is the fact that it doesn't need a timer. But an additional $20 is definitely worth it to pay for ensuring the quality of future weed. Besides, 24 hours with a LED lamp on will certainly raise your utility bill by a notable amount. 

12\12 Light Schedule

Another mode that showed to be viable is a 12\12 light cycle. While it will certainly land a satisfactory yield, the reduced light period in comparison to classic 18\6 will certainly diminish the potential maximum size of your plant. Mainly because the bush won’t make it to its full potential during the vegetative stage when the future yield gets determined by how big the plant was able to get. That being said, I would only opt for this mode if the electricity costs are crazy high at your place. Keep in mind that just like for 18\6 the timer is required.

How to ensure that the light is optimal if you grow outdoors?

While having full control over light when growing indoors is incredibly easy - thanks to timers and lamps, the plant that grows outdoors is certainly exposed to more risks. The rule of thumb - more intense light over a longer period means strong weed with high yields. Obviously, we can control it from one direction only - reducing the light if necessary. Of course unless you have mastered the magic and learned how to summon the heat with a shaman tambourine. For those who are lucky to live in tropical, subtropical, or Mediterranean climates everything should be just alright in terms of light exposure.

Cannabis under heat stress


The temperature is the only thing that is essential to control there. If it consistently hits over 30 °C don’t forget to regularly check the plant. Its leaves tend to curl up, wilt, or shrivel when the plant experiences overheating. In that case, it will be a good idea to move the plant to the shed during the peak of the sun intensity, which usually is between 12 and 2 pm.

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