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What is the Best Light Schedule for Autoflowering Cannabis?

Auto flower seeds can grow buds using any light schedule. However, you need to read this to find out which lighting schedule is best for them.

What is the Best Light Schedule for Autoflowering Cannabis?

Autoflower strains are the strain to grow when considering ease and convenience. Many growers choose to grow autos because they do not need a particular lighting schedule like the photoperiod plants. They start to grow buds once they’re mature enough (age-dependency) and not when they get enough light (light-dependency) like the photoperiod strains.

However, does this mean they do not need light at all? Not at all! Light is actually important in determining the yield you’ll get with most auto flower strains. Now that we know they love light, the next question is, “what is the best light schedule you can give your auto flower seeds to get an optimum yield?”. If you need an answer to that, then you’re in the right place.

This article will consider the various lighting schedules used for growing plants, the factors to consider before picking a lighting schedule, and everything you need to know about lighting for autoflowering cannabis plants. This is a must-read if you need a guide on the best lighting cycle for autoflowering plants.

Factors to Consider Before Picking a Light Schedule

If you’ve ever grown a strain before, you’ll know the four popular lighting schedules for cannabis strains. They include the 24/0 cycle, the 18/6 cycle, the 20/4 cycle, and the 12/12 cycle. For the newbies, the first number is the number of hours in light, while the 2nd is the number of hours of darkness. As we said earlier, any of this would get you buds from your autoflowering plants, so how do you know which to work with? You can use this checklist of factors as your guide:

  1. What is Your Lighting Budget?

The amount you’re willing to spend on light is important when picking your lighting schedule. For example, using 24 hours of light schedule for a month could rack up some serious electricity bills. So, if you’re on a leash regarding spending, the 18/6 or 12/12 lighting schedule might be a better choice.

  1. What Level of Yield is Satisfactory?

If you’re growing for your personal use, you might not be so concerned about the yield of the plants; so far, it’s enough for you. However, commercial sellers might want bigger yields per plant. If you’re not so concerned about the yield and have a tight spending budget, the 12/12 light cycle is a good choice. However, you would get much smaller yields compared to other strains.

  1. What Season are You Growing the Strains?

Growing in a cold or hot season also affects the type of lighting cycle you can use. For example, a 24/0 lighting cycle could be feasible when growing during winter as the weather is usually cold. This way, the lighting could help contribute to the heat. However, if you plant during the heat and use a 24/0 lighting cycle, you could overheat the room and cause adverse effects like wilting.

  1. What Spectrum of Light Can You Provide?

When growing auto flower cannabis strains, they require particular light spectrums for their vegetative and flowering stages. Blue light in the wavelength range of 400 - 550nm is best for their vegetative stage. For the flowering stage, red light in the wavelength range of 550 - 700nm is best. However, lighting that can provide the full spectrum is always considered the best option. Although, it wouldn’t matter if you could get the particular spectrums needed.

Which Lighting Schedule is the Best?

To know which lighting schedule is the best, we need to weigh the pros and cons of using each. So, we’ll be reviewing each of the four common ones. This would be a good place to note that many people experiment with other schedules apart from these four. However, it’s better to stick to one of these four when starting. Now that we’ve got that out of the way, let’s get to it!

  1. The 24/0 Light Schedule

As explained earlier, this would mean 24 hours of complete light with no dark period. Many growers claim this is good for autos when they’re in the vegetative stage as they require more light. Also, if you live in colder climes, this is good as it helps keep your plant warm by raising the growing room temperature. However, this could give you quite a heavy bill by the end of cultivation.


  • Beneficial for the vegetative stage.
  • Helps to warm plants in colder climates.


  • Heavy energy consumption.
  • The 20/4 Light Schedule

This schedule is perfect for those who do not want to rack up a bill like the 24 hours schedule but still want to give their plants as much light as possible. Also, the dark period gives the plants enough time to get some rest (if needed) and grow better. However, you might need a timer with this. And if your light isn’t automated, this will require physical attention.


  • Great balance for those who want to give autos as much light as possible.
  • It also gives time for plants to ‘rest.’


  • Requires physical attention
  • The 18/6 Light Schedule

This schedule is the best balance for most. This gives enough light to give a good yield and optimum rest periods. This would be a great choice for those in a hot clime as they can turn off the lights at the day's peak temperatures. Also, the light bill stays within safe limits. However, your attention is required to the timing of the lights.


  • The best balance for light and dark periods.
  • Great for those living in hot climes.
  • Light bills are not expensive.


  • Requires physical attention.
  • The 12/12 Light Schedule

This schedule is generally considered to hamper the yield from autos. They’ll generally give smaller buds and lower yields than other lighting cycles. People growing autos in the same room with photoperiod strains use this schedule. 


  • Good for those growing photoperiod strains with autos.
  • Saves a lot of money on electricity bills.


  • Gives smaller buds and yields.

Final Verdict

From the various light schedules considered, the 18/6 schedule is the best to go with, especially if you’re starting with a new strain. However, if you get a good yield, you might experiment with the 20/4 to see if you can get better yields. 

However, you should know that the yield and euphoric feeling your cannabis will give doesn’t depend on the light schedule. You need to get strains that can give a good yield and an even more perfect high. For example, the Purple Lemonade Auto and the Wedding Cake Auto at Herbie Seeds are two strains certified to give you the best of both worlds.