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Light Cycle for Weed

Understanding the light cycle for weed plants

Unless you’re a beginner, you should be familiar with the light cycle for weed. It’s an essential part of cultivating cannabis. Few people are aware of the important role it plays in the plant’s growth.

Marijuana plants that grow outdoors usually take the cue from seasonal changes to begin budding—unless they’re autoflowering of course. Towards the end of summer, when there are more hours of darkness than sunlight, weed plants enter the flowering phase.

Indoor cultivators use this knowledge to manipulate light cycles to create an environment where they can control how their crop responds to the stimuli.

The light cycle for weed can be a complex topic. We’ll help you understand lighting and how it affects your plant’s development. We’ll also look into the different types of schedules, and how to use it effectively during each stage of the growth process. 

A guide to the light cycle for weed

Although the term used is “light cycles”—it’s the length of darkness that determines when your marijuana plants move from the vegetative to flowering stage.

We’ll break it down into the following three growth phases:

  • Seedling
  • Vegetative
  • Flowering

Let’s jump in. 

Weed light schedule for seedlings

You can cultivate outdoors if you live in a warm area. Keep in mind that marijuana plants need humidity during the seedling phase. 

If the climate is not suitable, start your plants indoors and move them outside when the time is right.

Light Cycle for Weed

The inside seedling stage

At the cannabis seedling stage, you don’t require any extensive lighting setup. You can use compact fluorescent or LED bulbs. The optimal light schedule for seedlings is 18 hours of light and six hours of darkness.

The outside seedling stage

If your seedlings don’t get enough sunlight, you can use artificial lighting to extend the light period to 18 hours.

Cannabis vegetative lighting cycle

During the weed vegetative stage, your plant grows stems and leaves. During this phase, it focuses its energy on growing big and strong. 

Based on the cannabis light cycle, your crop will remain in the vegetative phase until it receives 12 hours of uninterrupted darkness—then it’ll begin to flower and produce buds.

Light Cycle for Weed

The inside vegetative stage

When growing indoors, you’re not dependent on sunlight and can control the marijuana light schedule. You can allow your plant to grow as big and tall as you want by giving it at least 18 hours of light every day.

Some cultivators increase the light to 24 hours per day, but we don’t recommend this because it can cause your plant to develop too quickly.

The outside vegetative stage

The marijuana light cycle for outdoor weed plants depends on the hours of sunlight in the day. Position your plant where it gets the most light.

Most growers prefer to keep their plants indoors under 18–24 hours of light before moving them outside for vegging. If you do this, make sure the outdoor conditions are suitable before the move. Snow or a sudden temperature drop can kill your crop overnight.

Marijuana flowering light cycle 

Similar to the seedling and vegetative stages of the growth process, there’s a light cycle for flowering cannabis. When marijuana plants receive more hours of darkness, they start to flower or produce buds.

Light Cycle for Weed

The inside flowering stage

If you’re cultivating indoors, mimic the change in seasons to switch your plant to flowering.

By adjusting the light cycle for weed to 12/12 hours of light and darkness, your plant should start producing buds for the next 8–12 weeks depending on the type of strain.

The outside flowering stage

You can expect the same flowering response once fall approaches when growing outdoors. In late June, the days are shorter and it’s dark for longer according to nature’s light cycle. You’ll see beautiful buds on your plant soon.

Light cycles for autoflowering plants

Autoflowering cultivars start flowering when they reach a certain age, so you don’t need to manipulate light cycles for your plant to begin flowering. 

If you want to generate the best possible yield, providing your crop with optimal lighting conditions is a step in the right direction. They don’t depend on light changes to start blooming though. 

Autos typically grow smaller than photoperiod strains because they spend less time in the vegetative phase. You’ll stimulate its robust growth by implementing a cannabis light cycle with a minimum of 18 hours of light.

Some cultivators achieve excellent results when they use a 24 hour light schedule. There’s no hard and fast rule to stick to. We suggest trying them out to see what works best for you.

If you want to save energy costs, a 12/12 marijuana light cycle offers a decent yield. The buds will be smaller than what you’d harvest when using the 18/6 and 24/0 schedules.

Light cycle scheduling provides a higher yield

 The marijuana harvesting stage is probably the most anticipated and satisfying part of growing weed. Light cycles are vital to your growing success. You can expect awesome yields if you’ve got the lighting down and you’ve properly fed and watered your plants.

The two stages in your plant’s growth that require optimal lighting are:

  • Vegetative
  • Flowering

During the vegetative phase, your plant will grow big and tall. Manipulating the weed light cycle can affect its size.

If you want a huge plant, use the 24/0 schedule. Otherwise, a minimum of 18 hours of light will suffice.

To force your plant into flowering, switch the marijuana lighting schedule to 12/12. Switch to an 18/6 or 24/0 schedule to increase the size of your buds once flowering has started.

Is it possible to provide your plants with excessive light?

Although you can manage and manipulate weed light cycles, it’s possible to over expose your plants to light. It usually happens when you position your grow lights too close to them. 

Even the best grow lights for cannabis can be detrimental to your plant’s health if placed incorrectly. Excessive heat can burn the leaves of your herb. The most obvious sign is leaves that are yellowish and appear burnt. 

Switching spectra: is it really necessary?

Yes. Switching spectra plays a big role in mimicking natural lighting

When using marijuana light cycles, you should consider spectrum colors. Different hues play unique roles in your weed plant’s growth, so you should switch colors during specific developmental stages.

The red spectrum is essential during your crop’s flowering stage because it gets the budding process going. 

  • Vegetative stage: bluer than red light.
  • Flowering stage: redder than blue light. 

Light disruption and power outages

Even if you use the best LED grow lights, there may be occasions when the light cycle for your weed is disrupted. Power outages are the most common culprits.

There’s no cause for concern as you can help your plants stick to a schedule by giving it some natural light during the “bright” period of the day. 

If you live in an area where these light disruptions are frequent, we suggest looking at long-term solutions such as a backup power source. 

FAQ related to light cycle for weed

We’ve rounded up some of the most common questions and answers about the light cycle for weed.

Is 24 hour light good for weed plants?

No, it’s not good for plants in the vegetative and flowering stages. A 24-hour light schedule for weed forces your plant to grow faster. Seedlings, on the other hand, need between 16–24 hours of light to stretch. 

How do you switch to a 12/12 light cycle?

To switch to a 12/12 schedule, keep your grow lights on for 12 hours and off for the next 12 to give your plant an equal amount of light and darkness every day. 

If you want to send a clear message to your herb that it’s flowering season, turn the lights off for 36 consecutive hours. After this period is over you can start the 12/12 cycle. This method kickstarts the flowering phase.

Can I change the light cycle during flowering? 

Yes, once your plant starts budding during the 12/12 light cycle, you can switch to a different schedule. You’ll likely get bigger buds than if you stick to the 12/12 one.

Can a weed plant get too much light? 

Excess light and intense heat can hurt your plant instead of helping it thrive. Your marijuana lighting schedule should mimic the natural light level of the sun’s rays as closely as possible when cultivating indoors.

Optimize light cycles to maximize yields

The light cycle for weed is an essential element in a marijuana plant’s growth and development. If you mimic nature’s lighting conditions in your indoor growing area, your cannabis plant will thrive and give you a bountiful harvest. The vital point to remember about light cycles is that it’s the dark period that determines when your plant starts to flower. Switch to a 12/12 schedule when you want the budding process to begin or simplify your life and grab some autoflowering seeds.

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