Light Adjustments For Autos — How Much Light Is Enough For Autoflower Cannabis Strains? - International Highlife

Light Adjustments For Autos — How Much Light Is Enough For Autoflower Cannabis Strains?

People can criticize autoflowering strains all they want, but even the harshest critic must admit autos take so much guesswork out of growing cannabis.

Sure, autos don’t produce the high returns you’d get with a “standard” sativa, indica, or hybrid. However, autos tend to be more resilient and thus more mistake-proof! If you’re a total newcomer to cannabis cultivation, you’ll likely have success with a batch of autoflower seeds versus non-auto cultivars.

Another reason autoflowers are so easy to work with is that they don’t require fancy light schedules. You won’t have to fret about the “best time” to switch from vegetative to flowering. No matter what lighting pattern you choose, autoflower strains will flower, well, “automatically!”

Of course, this “benefit” of autoflower strains opens a new can of worms. Namely, what’s the best lighting schedule for autoflowering cannabis? Is it better to blare your lights 24/7, or do autos need a breather daily to produce huge harvests? 

What’s The Best Lighting Schedule For Autoflower Plants?

As hinted in the intro, the light schedule for autoflower strains is incredibly flexible. Autos need some light to survive, but they are more resilient than non-auto cannabis strains. Whether you give your autos 12, 18, 20, or 24 hours of light per day, they should produce trichome-rich nugs — provided you’re taking proper care of their nutrient, water, and pH requirements. 

However, most autoflower cannabis cultivators argue it’s better to be generous with your light. The extra light will increase the likelihood of getting the maximum yield from your plants. Increased exposure to UV and IR may also help stimulate trichome production during the flowering stage.

There’s no rhyme or reason for choosing a lighting schedule for autoflowering cannabis, but many home-growers recommend at least 18 hours on and 6 hours off. If you don’t mind spending a little extra on electricity, you may want to experiment with a 20/4 schedule.

Also, it’s not unheard of for auto growers to keep their lights on 24 hours. While this may seem extreme, proponents claim autos can handle these long hours of light exposure. Why? Well, remember that Cannabis ruderalis (which all autos are related to) evolved in northern regions that experience all-day sunlight in the summer. 

Auto cannabis plants can survive with a 24-hour light cycle, but please remember this strategy will drive up your energy costs. Keeping lights on for a long time will result in more significant wear and tear on your bulbs. You may also notice “light burn” or excessively high temperatures if you keep your lights on 24/7.

For the best balance in energy efficiency and bud production, experiment with 18/6 and 20/4 light schedules for autoflowers. After testing these standard light patterns on various autoflower strains, you should know which method produces the best yields and what makes financial sense for your situation. 

Consider Your Climate When Choosing An Auto Light Schedule

While 18/6 and 20/4 are fantastic light schedules for most auto cultivators, please remember you don’t need to set these timers during the daytime. Most home-growers set their lights to turn on during the coolest hours of the day. 

It makes sense that you’d want your lights to provide extra warmth when it’s naturally cold outside. When it gets hot in your grow space, it’s a good idea to shut your lights off to avoid overheating your room. 

Please consider the average daytime temperature in your region to figure out when it’d make sense to set your light schedule. How long do your nights last? Are you in the middle of a frigid winter or a sweltering summer?

People who live in cold northern climates may do better with a more extended light schedule to produce more natural warmth. Conversely, those who live in subtropical areas tend to do better with the 18/6 light schedule because it reduces the risk of excessive heat. 

What’s So Wrong With A 12/12 Light Schedule For Autoflowers? 

Look, there’s nothing “terrible” about setting your lights to 12/12 for autoflowering plants. You’ll still get rewarded with juicy nugs once harvest time rolls around. However, chances are you won’t be as impressed with the results from an auto cannabis plant grown with 12 hours of light versus 18 or 20 hours. 

Autos will always produce less than non-auto cannabis strains, but they can make more buds if you give them extra light exposure. Autos use the energy from your lights to grow more bud sites and larger nugs. If you choose not to provide your autos extra light, then you won’t enjoy the max ROI from your seeds. 

Again, there’s nothing “wrong” with auto marijuana grown with a 12/12 light schedule. Just be prepared for a noticeably reduced total harvest if you opt for anything less than 18/6.

Does Lighting Alter The Harvest Time For Autoflower Strains?

The more light you give autoflowering cannabis plants, the faster they should grow. Indeed, this is one reason some people in the 24/0 camp argue their method is the “best.” Since autos with 24 hours of light are in constant growth mode, they usually reach flowering faster than other light methods.

However, how faster these 24/0 flowers reach harvest versus 18/6 or 20/4 is debatable. Also, it’s essential to remember each auto cannabis strain has a unique growing pattern. All these strains grow faster than standard hybrids, but different autos may be slightly slower than others. 

New cultivators should look up the average growth rate for their autoflower strain to get a feel for when they should look for the transition from vegetation to flowering. While these average times aren’t written in stone, they’ll give home-growers a good sense of when to expect peak harvest season.

Always inspect your cannabis buds with a jeweler’s loupe before deciding when to snip buds for harvest. Like classic cannabis strains, autos should have mostly pale white and amber trichomes when they’re ready for harvest. Clear trichomes are a “clear” sign it’s too early to harvest your nugs.

Generally, most autoflowering cannabis strains take about 8 – 10 weeks to go from seedling to full-flowering. However, please remember to rely on strain-specific details and visual cues to choose the best time to harvest your autoflowers. Also, remember that a longer “light on” schedule may increase your plant’s growth rate. 

Bonus Tip — Try Bending For Bountiful Autoflower Yields! 

While extra light exposure should increase your autoflower harvest, it’s not the only way to squeeze the most out of these hybrids. For instance, many cultivators use low-stress training (LST) to maximize light exposure on their plants. By taking the time to bend your cannabis branches with string, you’ll increase the odds of enjoying more trichome-rich nugs once harvest rolls around.

If you’d like to learn more about LST for cannabis buds, we’d recommend checking out our previous growing guide on “Cannabis Bonsai.” 

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