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Auto Flower vs Photo Period Overview

When people first start exploring the world of cannabis seeds, one question pops up again and again: should you choose autoflower seeds or photoperiod seeds?  Both are typically feminized, meaning they are bred to produce female plants. The real difference lies in how they decide when to flower.

One type flowers automatically on its own schedule. The other waits for a specific light cycle before it begins to bloom.

We offer both autoflower cannabis seeds and photoperiod cannabis seeds, giving collectors across Australia access to some of the finest genetics available.

The following guide provides a detailed overview to help you determine which strain type to buy

Auto Flowering

For faster finish, simplicity and multi-grows p/season

  • Switch into flowering mode  automatically after 3-5 weeks of growth, regardless of light schedule
  • Will take 8-12 weeks total (indoor or outdoors)
  • Grow smaller (approx 60-100cm tall)
  • If indoors, great for uniform plants and fast harvest
  • If outdoors, great for multiple harvests in a growing season

Photo Period

For larger yields and more control

  • Outdoors, will sustain vegetative growth up to 2 months before converting to flowering
  • Indoors, will switch to flowering whenever you switch the light cycle from 18 hrs on / 6 hrs off to 12 hours on / 12 hrs off cycle.
  • Outdoors, will take between 3-5 months total (depending on indoor vs outdoors)
  • Grow much larger (100-200cm+ tall) depending if grown indoor vs outdoors
  • If indoors, great for control (use light schedule to switch grow phase)
  • If outdoor, great for behemoth plants with insane yields 

What's actually the difference?

What Are Autoflower Cannabis Seeds?

Autoflower seeds contain genetics from Cannabis ruderalis, a naturally occurring subspecies that evolved in regions with short summers and unpredictable weather.

Rather than waiting for the days to shorten, these plants flower based on age.

Most autoflowers begin blooming around three to five weeks after germination and are ready to harvest in as little as eight to twelve weeks from seed.

They are compact, fast, and refreshingly uncomplicated.

For growers who enjoy instant gratification, autoflowers are the botanical equivalent of a friend who says, “No worries, I’ve already started.”

What Are Photoperiod Cannabis Seeds?

Photoperiod seeds rely on changes in day length to trigger flowering.

Indoors, growers usually maintain 18 hours of light during vegetative growth, then switch to a 12/12 light cycle to initiate flowering.

Outdoors, flowering begins naturally as the days become shorter later in the season.

This gives growers complete control over how large the plant becomes before it flowers.

If autoflowers are the spontaneous road trip, photoperiods are the meticulously planned cross-country adventure with snacks organised by colour.

The Main Difference Comes Down to Timing

Autoflower plants begin flowering automatically after a few weeks of growth, regardless of the light schedule.

Photoperiod plants remain in vegetative growth until they receive approximately 12 hours of uninterrupted darkness each day.

That one genetic difference affects nearly every aspect of the growing process, from speed and plant size to yield and training options.

Quick auto flower history lesson

Auto flowering first originated in the Cannabis ruderalis strain, discovered in Russia in the early 1940’s. We do not often use this strain on its own, due to the very low TCH levels (which is what gives you that ‘high’). Cannabis ruderalis is a wild cannabis type, grown in cooler and harsher climates, such as Russia, Eastern Europe, and Central Asia. In these climates, seasons are often short, with long cold winters.

In order for the plant to flower, before the change to the cold weather season, it adapted to flower automatically, to guarantee breeding and therefore, creating the auto flower gene. Ruderalis plants grow pretty small and only reach a height of around 2 feet and will start flowering after around 3 to 4 weeks. Ruderalis is the foundation of all auto flowering strains, which are usually a mix of the ruderalis strain with an indica or sativa type. 

Key Benefits of Auto Flower Seeds

  • Fast lifecycle – Seed to harvest in as little as 8–12 weeks, allowing multiple harvests per year.
  • No light cycle management – Flowers automatically based on age, removing the need for strict lighting schedules.
  • Beginner-friendly – More forgiving and easier to manage compared to photoperiod strains.
  • Compact size – Smaller plants are ideal for discreet grows, balconies, and small indoor setups.
  • Flexible growing conditions – Performs well both indoors and outdoors, even in less predictable climates

Key Weaknesses of Auto Flower Seeds

  • Lower yield per plant – Typically produces less than large photoperiod plants.
  • Less recovery time – Short lifecycle means early mistakes (watering, nutrients, stress) can’t be corrected easily.
  • Limited training options – High-stress techniques like topping can reduce yield or stunt growth.
  • Less control over plant size and timing – Cannot extend vegetative phase to increase size or yield.
  • Genetic quality varies – Poor-quality autoflower seeds can lead to inconsistent results, making breeder selection critical.

Growing and yield characteristics

Which Type Grows Faster?

Autoflower Seeds

Most autoflower strains finish in 8 to 12 weeks from seed to harvest.

Photoperiod Seeds

Photoperiod strains generally require 12 to 20 weeks, depending on how long they remain in vegetative growth.

If patience is not your strongest virtue, autoflowers tend to be the more satisfying option.

Plant Size and Space Requirements

Autoflowers are typically compact and discreet, making them ideal for:

  • Small grow tents
  • Balconies
  • Courtyards
  • Stealth setups

Photoperiod plants can be kept small or grown into very large specimens depending on how long they are allowed to vegetate.

This flexibility makes photoperiods ideal for growers who want maximum yield and have more available space.

Yield Potential

Photoperiod plants generally produce larger harvests per plant.

Their longer vegetative period allows for stronger root systems, more branches, and greater flower production.

Autoflowers produce smaller harvests per plant, but their rapid lifecycle allows multiple cycles in the same period.

It is the classic quality versus convenience debate, except both options can be outstanding.

Ease of Growing

Autoflower seeds are often considered the easiest option for beginners because:

  • They do not require light cycle changes
  • They finish quickly
  • They remain compact
  • They simplify planning

Photoperiod plants require more management, but they are also more forgiving because growers can extend the vegetative stage if problems occur.

Autoflowers keep moving whether you are ready or not.

Training and Advanced Techniques

Photoperiod plants are highly adaptable and respond well to:

  • Topping
  • Low-stress training
  • SCROG
  • Mainlining
  • Cloning

Autoflowers can be trained gently, but they have a shorter recovery window.

If you enjoy experimenting and shaping plant structure, photoperiod genetics offer far more flexibility.

Cloning and Genetic Preservation

Photoperiod plants can be cloned repeatedly and maintained indefinitely in vegetative growth.

Autoflower clones continue aging from the same biological timeline as the mother plant, making them impractical.

If preserving a favourite cultivar matters, photoperiod seeds are the superior choice.

Potency and Terpene Quality

Modern autoflowers have come a long way.

Top-tier autoflower strains can now rival photoperiods in potency, aroma, and resin production.

The outdated belief that autoflowers are weak belongs in the same category as dial-up internet and floppy disks.

Photoperiod strains still offer greater consistency and larger harvests, but the quality gap has narrowed dramatically.

Outdoor Growing in Australia

Australia’s diverse climates make both seed types useful.

Autoflower Advantages

  • Multiple planting windows
  • Fast harvests
  • Compact plants
  • Suitable for shorter seasons

Photoperiod Advantages

  • Larger plants
  • Bigger single-season yields
  • Excellent for full summer cycles

In warm regions such as Brisbane, Gold Coast and throughout Queensland, autoflowers can be started several times each year, while photoperiod plants can become impressively large under favourable conditions.

 

Honest comparison

When Autoflower Seeds Make the Most Sense

Autoflower genetics are ideal if you want:

  • Fast results
  • Simple growing
  • Smaller plants
  • Multiple annual cycles
  • Minimal setup complexity

Browse our full range of feminized autoflower cannabis seeds.

When Photoperiod Seeds Are the Better Choice

Photoperiod genetics are best if you want:

  • Maximum harvest potential
  • Full control over plant size
  • Advanced training options
  • Reliable cloning
  • Long-term preservation of genetics

Explore our complete selection of feminized photoperiod cannabis seeds.

Auto vs Photo Period FAQ

Autoflower cannabis seeds produce plants that flower automatically based on age rather than light cycles.  Typically, the plant will start showing sex at approx 4 to 5 weeks into the vegetable cycle, and then will quickly transition from vegetative into flowering, enabling a faster growing cycle and early harvest.

Most autoflowers are ready to harvest in 8 to 12 weeks from seed.

Yes. They’re one of the simplest types of cannabis to grow due to their compact size, ease and resilience.

The latest Auto genetics are so incredible, producing yields that often surprise cannabis growers.    Per plant, yes of course, they yield less than photo period plants, however if you weigh up the speed of harvest and multiple crops, it’s highly debatable which option can actually yield more on a total yearly basis….

Yes, they’re well-suited for Australian conditions due to their rapid lifecycle and flexibility.   In many parts of Australia, you can grow Cannabis all year round and Auto’s allow you to compress the growing period so you can sneak a quick grow into a period that normally would not be possible for photo periods.

No. They grow well under a consistent light schedule however it’s definitely worth ensuring you have the right lighting spectrum for the flowering phase for best results.  They’ll flower regardless, but to get the most out of them, you’ll still want to ensure the right light spectrum.

Yes, but low-stress training is preferred to avoid stunting growth.

Nope.  Not anymore, modern strains can reach THC levels similar to photoperiod varieties.  It’s actually crazy when you see how fast they grow.  If you have never grown auto’s it’s worth trying so you can see the difference and then assess what works best for you in future. 

Most stay between 60 and 100 cm, making them compact and discreet.

Photo Period Cannabis Seed Strains

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AUTO FLOWER Cannabis Seed Strains

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About the author:

As a passionate gardener and advocate for self sufficiency and food security, CG aims for moderation and reverence of Cannabis as an ancient and powerful natural medicine.  As the taboo steadily lifts worldwide, we’re here to help responsible, law abiding adults to experience the joy and wonder of nurturing a tiny seed from humble germination to bountiful harvest.

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