best light cycle for autoflowers

The dance of light and darkness: it’s the fundamental rhythm autoflowers groove to, and optimizing it can make all the difference. So, what’s the ideal light cycle for autoflowers? The majority of growers favor 18 hours of light and 6 hours of darkness, but is this the best light schedule for your autos? And do 24 hour light cycles over stress your plants?

This article guides you through the specifics of autoflower light cycles, from germination to harvest. We’ll illuminate the science behind light exposure, explore varying schedules, and shine a spotlight on which allows you to maximize yield. 

By the end of this read, you’ll be armed with practical tips to keep your autoflowers flourishing under the most favorable conditions. Let there be light – and knowledge!

What are the different light cycles for autoflowers?

In your journey to finding the perfect autoflower light cycle, understanding the different photoperiods is key. Typically, three main light schedules are employed by autoflower growers:

The 24 hour autoflower light cycle

The 24/0 light cycle involves keeping lights on around the clock without giving the plants any dark period. This method stimulates rapid growth as it maximizes photosynthesis by providing continuous light. It’s often used by growers who want to push their autoflowers to the limit in terms of vegetative growth, and it may be useful for northern growers with a very short outdoor growing season who need to maximize growth indoors before moving plants outside. However, some growers believe this schedule can cause plants to become stressed from the constant light. Also, it can lead to higher electricity costs.

The 20/4 autoflower light cycle

The 20/4 light cycle, meaning 20 hours of light and 4 hours of darkness, strikes a balance between promoting robust growth and allowing plants some downtime. It is a great middle ground that still provides plenty of light while allowing some recovery time, ensuring the plant isn’t overwhelmed. This cycle is beneficial for those who seek vigorous growth but want to avoid the potential stress associated with a 24/0 schedule. The downside is that it still uses more electricity than the 18/6 cycle, and there’s a slight risk of stressing the plant compared to the more conservative light schedules.

The 18/6 autoflower light cycle

The 18/6 light cycle is the most popular schedule among many autoflower growers. It gives plants 18 hours of light and 6 hours of darkness, closely mimicking the long days of summer while providing enough darkness for the plant to rest. This schedule is considered the least likely to stress plants and has the added benefit of reducing energy usage compared to the 24/0 and 20/4 light cycles. It’s ideal for those who aim for a more natural growth cycle and want to conserve energy. However, its downside is that it might offer slightly slower growth compared to the other two more intense light schedules.

What is the best light cycle for Autoflowers?

The “best” autoflower light cycle can be subjective and may depend on specific growing conditions and goals. However, a large number of cultivators favor the 18/6 light cycle for autoflowers – 18 hours of light and 6 hours of darkness. This schedule provides ample light for photosynthesis and growth, while also giving the plants a sufficient dark period for rest and metabolic processes. 

It’s a solid balance that mimics natural conditions, supports healthy growth, and promotes impressive yields, making it a popular choice. Still, the “best” can vary based on factors like strain characteristics and energy costs. Let’s shed some more light on these considerations next.

Light CycleProsCons
24 hours lightMaximizes photosynthesis and growth potentialCan over-stress and tire the plant
20 hours light, 4 hours darkGood middle ground; provides ample light while allowing recoveryMore energy usage compared to 18/6 cycle; slight risk of stress
18 hours light, 6 hours darkMost popular schedule; least likely to stress plantsSlower growth compared to 24/0 and 20/4 cycles

Do Autoflowers like intense light?

Autoflowers can handle intense light pretty well. Being descendants of Cannabis ruderalis, a species adapted to harsh conditions, they can tolerate more intense light than you might think.

However, the keyword here is “tolerate.” While they can withstand intense light, it doesn’t necessarily mean it’s optimal or beneficial for them. Excessive light intensity can lead to issues like light burn, causing damage to your plants. 

Therefore, it’s crucial to strike the right balance when deciding on the intensity of light for your autoflower light cycle. We’ll explore how to find this balance in the following section. This is why by using either an 18/6 or 20/4 cycle allows your plants plenty of time for rest and recovery inbetween intense periods of light.

What is the ideal light spectrum for autoflowers?

Light spectrum relates to the different colors or wavelengths of light. When growing plants, we often focus on three main segments of the light spectrum: blue, red, and far-red.

Blue light, typically seen in 6500K bulbs, falls around 400-500 nanometers in the light spectrum and is fundamental during the plant’s vegetative growth phase. This part of the light spectrum supports the development of robust stems and healthy leaves, encouraging a bushy, compact plant structure and preventing excessive stretching.

Red light, often represented by 2700K bulbs, falls around 600-700 nanometers on the spectrum and is essential during the flowering stage. It encourages bud formation, enhances the size of flowers, and impacts the overall yield. This light spectrum acts as a cue for plants to enter their reproductive phase, thereby stimulating blooming.

Far-red light, with wavelengths over 700 nanometers, also plays a role in how the plant perceives day length, and can assist with germination and elongation of stems, though it is less directly involved in photosynthesis.

For autoflowering plants, lights that provide a full spectrum are generally considered the best choice. Full-spectrum lights provide all necessary wavelengths, encompassing both the blue and red regions of the light spectrum and everything in between. These lights replicate natural sunlight as closely as possible, offering autoflowering plants the balanced light spectrum they need for both vegetative growth and flowering. Full-spectrum LED lights are particularly favored for their efficiency, durability, and their ability to produce a wide spectrum of light that autoflowers require throughout their entire lifecycle.

Light SpectrumColor TemperatureWavelength (nm)Stage of Autoflower GrowthRole
Blue Light6500K400-500VegetativePromotes development of strong stems and leaves, maintains compact growth, prevents excessive stretching.
Red Light2700K600-700FloweringEncourages budding, increases flower size, impacts overall yield, signals plants to enter reproductive phase.
Full Spectrum LightN/A400-700+Vegetative and FloweringSimulates natural sunlight, provides a balanced light spectrum for all growth stages. Ideal for autoflowers.

How many days do Autoflowers bloom?

Autoflowers, renowned for their speedy growth, typically bloom for around 30 to 50 days. This flowering phase kicks in after a short vegetative period, which usually lasts for two to four weeks. 

Thus, the total lifespan of an autoflower, from seed to harvest, is generally between 70 to 90 days. However, this timeline can fluctuate based on factors like strain, growing conditions, and light cycle. 

The beauty of autoflowers lies in their simplicity – they transition to bloom based on age rather than light cycle changes. However, to maximize their bloom phase and yield, certain strategies come into play, which we’ll discuss next.

When should I switch to 12 12 light cycle?

In the case of autoflowers, the short answer is: you don’t need to switch to a 12/12 light cycle. Unlike photoperiod strains that require a shift in light cycle to trigger flowering, autoflowers are genetically programmed to start flowering based on their age, not light changes. 

They begin blooming regardless of the light schedule, usually thriving best under a consistent 18/6 or 20/4 light cycle throughout their lifecycle. Implementing a 12/12 light cycle for autoflowers will simply lead to lower yields due to less light exposure.

While it may save energy, the trade-off in yield may not be worth it for most growers. Up next, we’ll touch on some frequently asked questions about autoflower light cycles.

Growing autoflowers alongside photoperiod (feminized) strains

Growing autoflowering cannabis strains under a 12/12 light cycle within a tent containing some photoperiod plants is a strategic way to utilize any leftover space. This method combines the different types of plants to maximize the use of the growing area. Autoflowers are not dependent on the light cycle to start flowering and can thrive under 12/12 just as they would under a longer light schedule. Their compact size and shorter lifecycle make them ideal for filling up gaps that would otherwise be left unutilized. Meanwhile, the photoperiod strains will receive the light schedule they need to shift from vegetative growth to flowering. In this setup, you create a synergy that ensures all spaces are occupied, and every bit of light is used effectively. It’s a resourceful and efficient approach to get the most out of your grow space.

Can Autoflowers grow without light?

Light is crucial for all plants, and autoflowers are no exception. Without light, photosynthesis – the process by which plants convert light energy into chemical energy to fuel their growth – cannot occur. In the absence of this process, your autoflowers simply won’t be able to grow. 

They need light, and plenty of it, to thrive. However, this doesn’t mean they require 24 hours of light a day. A balanced autoflower light cycle that includes periods of darkness is beneficial, as it allows the plant to rest and carry out essential metabolic processes. 

So, no light equals no life for your autoflowers. Now let’s switch gears and look at some ways to optimize your light setup for autoflowers.

Do Autoflowers need a dark period?

While autoflowers aren’t dependent on a dark period to trigger flowering like their photoperiod counterparts, they still benefit from some amount of darkness. The dark phase allows the plant to rest and conduct essential physiological activities that contribute to its growth and overall health. 

A common practice is to follow the 18/6 light cycle – 18 hours of light and 6 hours of darkness. This mimics natural conditions and provides a balanced autoflower light cycle that fosters optimal growth. 

Remember, while light fuels photosynthesis and growth, a rest period can prove beneficial too. Next, let’s discuss how to monitor your autoflowers during different light cycles.

How do I know if my Autoflower has too much light?

autoflower under bright light

It’s important to be aware of the signs that indicate your autoflower may be receiving too much light. Keep an eye out for leaf discoloration, such as yellowing or light bleaching with white or brown spots, as these can be indicators of light stress or burn. 

Another sign to watch for is leaf curling, where the leaves take on a taco-like shape, which can occur as a protective response to intense light exposure. If your autoflower seems smaller than expected or is experiencing stunted growth despite favorable conditions, it could be a result of excessive light. 

Additionally, be mindful of heat stress caused by high temperatures resulting from intense light. If you notice any of these signs, you can address the issue by raising the light source further away from the plants, using shading techniques, or utilizing light-diffusing materials to reduce light intensity. 

By closely monitoring your autoflowers and making necessary adjustments, you can ensure they receive the optimal amount of light for healthy growth.

Joe Musgrave

An avid 420 enthusiast, grower, smoker and writer. Joe writes non stop, sharing his extensive knowledge in the field of cannabis with the wider online 420 community through blogs like ours at High Yield Strains.

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