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The Perfect Light Schedules For Autoflower Cannabis

Growing autoflower strains? In this article, we explore the ideal light schedule to help your autos produce the best possible harvests.

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25 Nov 2019

By Steven Voser

Contents:

What’s the best light schedule for autoflower cannabis?

WHAT’S THE BEST LIGHT SCHEDULE FOR AUTOFLOWER CANNABIS?

Autoflowering cannabis strains flower based on age , rather than a change to their light cycle. Nonetheless, providing your autos with the right amount of light remains crucial to ensuring the best possible harvest. Read on to learn all there is to know about lighting for autoflower cannabis strains.

Video id: 527684146

18/6 LIGHT CYCLE

Cannabis is a C3 plant, meaning it can absorb CO₂ for photosynthesis even during light hours. And since autoflowering plants have short vegetative phases and often grow shorter than photoperiod strains, you’ll typically want to give your autos at least 18 hours of light. This allows for robust growth, without overspending on energy. Your autos love light just as much as traditional photoperiod strains, they just don't rely on it to begin bloom.

24HR LIGHT CYCLE

Some growers will even give their autos a full 24 hours of light, arguing that this helps maximise vegetative growth. Growers who stick to 18-hour light cycles, on the other hand, argue that this gives their plants a short “recovery” period that is essential for healthy growth.

There’s no real consensus on whether autos grow better under 18 or 24 hours of light, and we’ve seen growers achieve great results with both methods. To make up your mind, we recommend playing around with both variations and sticking to what works best for you.

WHAT’S THE BEST LIGHT SCHEDULE FOR AUTOFLOWERING CANNABIS?

WHAT ABOUT A 12/12 LIGHT CYCLE?

Some growers still decide to keep their autos under a 12/12 light cycle during flowering. And that’s fine, as autos grown in these conditions can still produce a fair harvest. Just remember that the buds you harvest under a 12hr light cycle will be noticeably smaller than what you'd get under a 18–24hr cycle. Some reasons you might consider keeping your autos under 12/12 include:

Heat concerns: If you live in a very hot climate, you might want to turn your grow lights off during the day to avoid overheating your grow room. In that case, growing your autos under a 12/12 light cycle—with lights on during the night—might be your best bet to avoid causing your plants heat stress.
Growing autos alongside photoperiod strains: If you’re growing autos alongside feminised photoperiod strains, you’ll likely have to place your autos in the same room as your flowering feminised plants, meaning your autos will only get 12 hours of light per day.
To save money: Running grow lights for 18–24 hours over a few months can get very expensive. If you want to grow autos on a tight budget, you might want to use a 12hr light cycle instead.

PERFORMING SOG WITH AUTOFLOWERS

SOG, or sea of green, is a cannabis training technique that can produce some great harvests. Rather than getting your plants to grow as large as possible, SOG involves growing several smaller plants in close proximity to form a uniform canopy that maximises light exposure and space.

SOG is a great technique to try with autos because it takes advantage of the naturally smaller stature of these varieties.

While every grower will have their own technique for SOG, most will grow between 4–16 plants per m², depending on how big they let each plant grow.

Depending on the size of the particular strain you’re growing, we recommend using 7–10l pots and growing between 4–6 plants per m². This should make the most of your space and lighting while still providing your plants with enough airflow to avoid any mould issues. If you decide to grow more plants per m², remember to use smaller pots to control their size and avoid overcrowding your grow room.

A NOTE ON LIGHT SPECTRUM

Using the right light spectrum is super important when growing any type of cannabis plant, including autos. Because autoflower plants have such short life cycles, you really want to maximise the quality of light, nutrients, and soil you give them.

As you might recall from science class, when you shine a light through a prism, it is broken up into different colour spectrums. Plants, which depend on light for photosynthesis, respond differently to these different spectrums. Like with a photoperiod cannabis strain, we recommend sticking to the following light spectrums:

6500K blue light during veg: Blue light spectrums have been shown to encourage vegetative growth, helping cannabis plants grow short and stocky while minimising stretching.

2700K red light during flowering: Red light spectrums are ideal for bloom because they encourage budding and a little bit of stretch, encouraging your plants to produce big, dense flowers.

EXTRA TIPS FOR GROWING GREAT AUTOS

If you’re new to the world of autoflowers, follow these simple tips for a better harvest:

Pick a high-yielding auto: Not all autoflowers are made equal, so be sure to pick a high-yielding strain if harvest size is important to you.
Plant in your final container: Up-potting cannabis plants always causes stress. Since autoflowers can go from seed to harvest in as little as 8 weeks, it’s best to avoid this kind of stress and always plant your seeds straight into their final pots.
Use an airy growing medium: This helps stimulate root and foliage growth.
Use LST: If you want to train your autoflowering cannabis plants, only use low-stress techniques. High-stress techniques like fimming, topping, and supercropping will end up doing more harm than good.

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