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Cannabis Flowering Types

Cannabis Flowering Types:  Photoperiodism vs Autoflowers

For Cannabis, there are two Flowering Types; Photoperiod & Autoflowering.  For the novice farmer, and quite a few legal growers, autoflower cannabis plants are becoming the new norm.   To figure out why, let’s look at what the differences are between photo cannabis plants and autoflower cannabis plants.  Let’s first start with defining photoperiod and autoflowering plants, and then we can list the major advantages and disadvantages associated with each type.


Photoperiodism is the term for cannabis plants that flower due to the amount of light and darkness they receive during a  given day. Photo plants start to flower when they sense that the light/darkness split is close to 50/50. This is the basis of the classic 12 hours of light, 12 hours of complete darkness that most growers recommend for photo cannabis plants.


Autoflowering cannabis plants flower on the basis of an internal clock inside the plant.  Regardless of the amount of light or darkness the plant receives, it will begin to flower within a set number of days from germination.  Whether the plant gets 18 hours a day of light or 10 hours of day of light, it will not effect when the plant begins to flower. Many autoflowers will be ready to harvest in 9-12 weeks from seed.  There are now Super Autos which are still autoflowering, but have a longer lifespan that can reach up to 15-16 weeks. These Super Autos are meant for higher yields, but the longer lifespan means less possible crops per year. 

Autoflower Advantages
  • Can be kept short in stature for “stealth” growing
  • Short life span.  Quick to harvest, and issues during grows(fungus, mold, mites, etc) result in less lost time.
  • No need for a separate vegetative and flowering environments.  This enables the perpetual harvest.
  • Can be grown in northern climates where summers are short.
  • Can be grown outside in city environment.
  • Can produce multiple harvests outdoors in one season
Autoflower Disadvantages
  • Smaller yields due to the plant’s short vegetative and life spans.
  • New seeds needed for every grow.  
  • Cannot clone autoflowers.
  • THC and CBD levels are typically 10-20% lower than the strains’ photoperiod equivalent.
Photoperiod Advantages
  • Can set vegetative period from one month to several months.
  • Can be grown to 10’ in height outdoors and yield several pounds or kilograms.
  • Typically have higher THC, CBD amounts that a similar autoflowering strain.  This difference can be 10-20% or more.
  • Can be cloned.  This negates the need for new seed purchases.
Photoperiod Disadvantages
  • Indoors must be kept separate from vegetative plants when flowering.  Thus you cannot have a perpetual harvest of photo plants when growing indoors.
  • Difficult to grow in cold environments outdoors.  
  • Typically limited to one harvest per season
  • Cannot be grown outdoors near or in city environments where ambient light is always present.

Now that you know the difference between autoflowering and photoperiod cannabis plants, you can make the best decision for your situation.   It is easy to see why more and more small, private growers are switching to autoflowering plants due to their simplicity and ability to provide continual harvests for personal use.  Even at a cost of $10/seed, an autoflower easily pays its cost many times over. Thus the cost of new seeds for each grow, the main autoflower disadvantage vs photoperiod plants that can be cloned, is really nominal in the long run.  

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