How To Tell When Autoflower Is Flowering: Week-by-Week Grow

How autoflowers flower, what signs to look for, the right time to harvest, the right nutrients to give them and much more…
08 April 2020
9 min read
How To Tell When Autoflower Is Flowering: Week-by-Week Grow

  • 1. The vegetative stage of your cannabis plant
  • 1. a. Week 1 - week 4: vegetative state
  • 2. The pre-flowering stage
  • 2. a. Week 5: the appearance of stigmas
  • 2. b. How to recognize pre-flowers?
  • 2. c. Autoflower not flowering?
  • 3. The flowering stage
  • 3. a. Week 6: stigmas in abundance
  • 3. b. What are stigmas?
  • 3. c. Week 7: development of trichomes
  • 3. d. What are trichomes?
  • 3. e. Week 8: calyxes fattening up
  • 3. f. What are calyxes?
  • 3. g. Week 9: harvesting time
  • 4. How to tell if my auto is ready?
  • 5. In conclusion

If you’re new to growing autos, you may not know how these plants flower. Read along to know exactly what to look for, signs of pre-flowers, when the plants are in full bloom, and what to consider when growing autos.

For those who are new to growing autoflowering Cannabis plants, you may be unaware of exactly how these plants flower. As you may know, autoflowers start flowering automatically, without the need of changing the light cycle. Despite the minor differences between photos and autos, both will show the same signs when flowering such as white hairs, trichomes, and dense calyxes.


Sebastian Good tells you all signs to identify the Stage your Autoflowering Cannabis is in.

1. The Vegetative Stage of Your Cannabis Plant 

Week 1 - Week 4: Vegetative State 

Depending on the genetics you’re growing, there will be a growth period of around 4-5 weeks, during this time your cannabis plants will focus on developing green matter such as roots, branches, foliage, and establishing itself structure-wise prior to flowering. 

All of these parts of a plant are essential to cannabis because they’re used in vital processes such as transpiration which helps plants regulate the temperature and photosynthesis which is used to produce sugars used on plant growth.


How to tell when autoflower is flowering: the vegetative stage

The vegetative stage of cannabis plants.

Also, all of this growth is what will allow your plant to withstand the weight of the buds during the flowering stage, as you may know, some plants produce super heavy flowers and if your plant hasn’t developed properly you’ll need to provide support or the branches may end up snapping.

During this stage, there will be no signs of flowers and this is also the ideal window to apply plant training to your autoflowering plants.

  • Focusing on stems, branches, and foliage development.
  • Roots will grow and anchor into the growing medium.
  • The ideal time to use techniques such as topping and L.S.T.
  • Higher amounts of Nitrogen will be needed during this time.

2. The pre-flowering stage

Week 5: The appearance of stigmas

No matter what time of the year outside you decide to grow your autos, after the fourth week of growth the plants will begin to transition into the pre-flowering stage. This means they will shift in auxin production and focus on flowering causing a hormonal change and a preference for certain nutrients. When your plants start flowering you have to make sure that you're providing higher doses of phosphorus and potassium, these are the main minerals your cannabis plants need to produce buds.


How to tell when autoflower is flowering: stigmas

First signs of flowers appearing on a cannabis plant.

Apart from these two, cannabis plants also need micronutrients, these minerals are needed in much lower doses, and depending on the type of medium you're growing in, you will have to provide them with products such as CalMag additives.

Other than Calcium and Magnesium, your plants also need Iron, Sulfur, Copper, and Zinc among others, and even though they are used in small quantities, your plant won't perform as well if they're not available so make sure they are.


How to tell when autoflower is flowering: pre-flowering stage

Photo courtesy of BigBadLion.

You can measure the amount of minerals present in your water source by using a TDS meter but you won't know exactly what's in it, so the only way to know exactly what's present is to filter your water and add the minerals to the desired quantity.

It is from this point onwards that the plants will continue to fully bloom until the harvest date.

  • Autoflowering plants will stop focusing on root development.
  • The plants will go through a hormonal growth spurt causing them to stretch.
  • Pre-flowers will appear in abundance very quickly after 4 weeks.
  • Avoid training your plants at this point, especially topping.
  • Plants will be more dependent on higher amounts of P-K now until harvest.

How To Recognize Pre-Flowers?

From the start of the pre-flowering stage until the end of your plant’s life cycle you’ll see an abundance of white hairs growing all over, these white hairs (stigmas) are a sign of a female cannabis plant.

These long hairs emerge from the calyxes and are responsible for capturing pollen to produce seeds but usually, home growers don’t make seeds so these hairs won’t wilt and brown until the last couple of weeks of the flowering stage.

Autoflower Not Flowering?

As you may know by now, after 3-5 weeks your autoflower should be transitioning to the flowering stage but if the weeks go by and you don't see any signs of stigmas (white hairs) there are a couple of things that could be causing this.

First of all, you need to remember that the information most breeders specify is when growing their genetics in optimal conditions so if you don't have a good light fixture, nutrients and are not controlling the conditions, your plants may take a bit longer but don't worry, they will flower.

Another factor that could have an influence is the phenotype you get, this happens because autoflowers are hybrids, which means they contain a mix of genetics, and the percentage of Indica, Sativa, and Ruderalis in each specific cultivar may vary so even if you are growing a strain that the breeder specifies it takes around 10 weeks, your plants could take a bit less  (8-9 weeks) or a bit longer (11-12 weeks), depending on the phenotype and conditions provided.

3. The flowering stage 

After your plant has already started showing signs of flowers, you’re officially in the flowering stage, even though your plant won’t grow more leaves or branches, she will still grow quite a bit through a process called “flowering stretch” and you will see the flowers getting denser as time goes by.

Week 6: Stigmas in abundance 

The sixth week into flowering is when you’ll see your buds really starting to develop, at this stage your plant will start producing a lot of hairs and you’ll definitely see your plant full-on flowering.

As shown, the white hairs start super long and almost clear, and as time goes by they will brown and wilt, also looking shorter, this is because the calyxes which is where stigmas grow in are getting denser.


How to tell when autoflower is flowering: week 6

Super long stigmas on a cannabis plant courtesy of BigDaddyK.

You will see a lot of hairs all over the flowering sites, these hairs are a sign that your plant is sexually mature and can now produce buds or seeds if it gets pollinated, you’ll also see the trichomes starting to appear with the stigmas, even though you won’t see a lot of resin right now because your plants have just started producing them, you will definitely be able to smell that sweet cannabis aroma.

What Are Stigmas?

Pre-flowers are the first signs of a female plant and the stigmas will start to appear, looking like small white, fuzzy hair. This is actually what ends up as the brown hair wrapped around your dried buds, and is the start of life for bud production. 

Stigmas can be found on the flowering sites and as the plant develops, starting from the pre-flowering stage and onwards, the entire plant will become filled with thousands of long white hairs.

The name of the white hair is stigma and will emerge from the calyxes. As the female sex organ, it is the stigma that must come into direct contact with the pollen in order to produce seeds.

Week 7: Development of trichomes 

In the seventh week of flowering you will probably see an abundance of resin all over the buds and surrounding foliage, this is when you’ll definitely need a carbon filter or any other way to mask the strong cannabis aroma.

In the image below you can clearly see a bit of resin starting to form although it is not as abundant as when the buds are ready for harvest, this is a sign that your plant has just transitioned from the vegetative stage to the flowering stage and will gradually start to fatten up the buds and producing a lot of resin.


How to tell when autoflower is flowering: week 7

Trichomes starting to appear on week 7 of flowering by Shinsimilla's.

The trichomes produce and store all the sweet compounds you love so it’s essential you provide good conditions because the trichomes are volatile and can be degraded by physical contact, excessive heat, oxygen, and light

Remember that trichomes produce and store the terpenes which are responsible for the smell, in most cases, when cannabis plants start producing trichomes they will start smelling really strong so depending on where you’re growing and the setup, now it’s a good time to deal with it.

What are trichomes? 

Trichomes form the resin you can clearly see on the buds and surrounding plant material, the trichome glands produce and store flavonoids, terpenes, and cannabinoids which are the compounds responsible for the effect, aroma, and flavor you’ll get when smoking your cannabis buds.

The trichomes are also responsible for protecting the buds against UV rays and bugs so if you see trichomes on your plant, it means the buds have already started developing or are right about to start.

Week 8: Calyxes fattening up

Week 8 into flowering is the week before the last, your buds will be relatively denser and will give you an idea of how they will turn out after harvesting, another good way to know if your plant is flowering is when the calyxes become plump.

As you can see in the image below, even though the plant still needs a couple of days, the calyxes are super fat and round, meaning this plant won’t fatten a lot more but isn’t completely mature yet.


How to tell when autoflower is flowering: week 8

Cannabis plant on week 8 of flowering by DabNinja710.

When the calyxes have become plump and are visibly dense, it means your plant is almost ready to be harvested, it just needs a bit longer to ripen and you’ll be all set.

This happens because the calyxes are what protect the seeds which is how cannabis plants guarantee their next generation so if a plant has not been germinated and the calyxes are round and plump, it means the reproduction phase has ended and your plants are ready to finish their life cycle.

What are calyxes? 

The calyxes are the first part that is formed when a cannabis plant enters the flowering stage, this structure is designed for protecting the plant’s reproductive organs and is where the stigmas come out.

Even though both male and female plants have calyxes, only the female plants are what matters to most home growers because the calyxes are what form the flowers you’ll end up smoking.

Week 9: Harvesting time 

In the last week of flowering, you’ll see the stigmas wilting and browning, when this happens, it’s a sign that the buds are ripening and it will only take a couple of days to be chopped down.


One of our growers showing off his flowering plant.

When your plants have completely matured and the stigmas have turned brown, your plant won’t take more than just a couple of days to be completely mature, at this stage you’re just waiting on the state of the trichomes to harvest your buds at the right time.

3. How to tell if my auto is ready?

The pistils, trichomes, and calyxes are signs that the plants are close to harvesting and the trichome development is fully or almost fully mature. Now just because the hairs have turned brown does not mean you should grab your trimming scissors and eagerly get to work, however, there are a few other things you should check:

1. The stigmas have completely turned brown and wilted, this means your plants have already gone through the reproduction stage and is almost nearing the end of its life cycle.

2. The calyx has fully bulged, becoming as swollen as possible giving the buds a compact appearance. It is better to wait for the buds to be as fat as they can be before harvesting, even if all the hairs are and the trichomes are fully matured.

3. Using a high-powered lens and examine the state of your trichomes. You will notice the head of the trichome will be either clear, milky, silver, or amber-colored. Harvesting your autoflowering plants when the trichomes are milky to amber will provide better effects.


Best time to harvest based on the trichomes

State of the trichomesEffect
ClearStill unripe, not too potent.
CloudyAt their peak potency.
AmberTHC degraded into CBN, more corporal effect.


Remember that you don't need to follow this table but it may be of help, by knowing exactly what effect each state of the trichomes provide you can fine-tune your harvest when your plants will provide the desired effect, so for example, you don't want a super-strong head rush, you can harvest when 50/50 of the trichomes are amber and cloudy, resulting ina more balanced effect.

5. In Conclusion

It is very important when growing autoflowering cultivars to know what to look for, as well as what to feed them. Once you have achieved the perfect balance in the feeding department. Getting familiar with different cultivars can take time and experience. The diversity of autoflowering Cannabis is at its pinnacle, with so many hybrids with a wide variety of different traits.

Good luck growing your autos this year and we hope this article will help you on your way to growing some incredible crops!



External References:

  1. TRICHOMES OF CANNABIS SATIVA L. (CANNABACEAE) - Dayanandan, P. & Kaufman, Peter. (1976). 
  2. Pollen-Pistil Interaction and Fertilization. - Shivanna, K. (2020).  
08 April 2020