Cannabis Flowering Stage
From the Stretch to Harvest
Hey there and welcome (back) to Free The Tree!
In this series of the cycle of life of weed we’re going to cover the cannabis flowering stage. This is one exciting part of her life!
If you’re looking for marijuana flowering stage tips you’ve come to the right place. You won’t see her grow as much is size anymore, but her flowers will develop oh so nicely, starting from small pistils to buddlets and then full grow flowers, by the last stage you won’t even recognize them anymore.
Take some pics to compare the evolution! Don’t hesitate to send them to us if you want come share them with the FT community.
Marijuana Flowering Stage – Table of Content
- Characteristics of the flowering stage
- PK – Flowering Stage Nutrients
- The Stretch
- Early Flowering Stage
- Trichome Appearance
- Late Flowering Stage
- Flushing your plants
- Flowering week by week
Let’s get into it
Characteristics of the flowering stage
Pretty quickly after changing the light cycle from 18/6 to 12/12 your plant will show changes. For first 2 weeks it’s basically the vegetative stage on steroids (known as “the stretch”).
This is a bit like our teenage years, strong growth followed by hormones; in the case of Cannabis after the growth pistils will start appearing, welcome to the flowering stage 🙂 Here’s what to expect
|Macro-Nutrients needed||After the stretch the plant will need mainly Phosphorous and Potassium (PK)|
|Vegetative Growth||Once the stretch has ended, vegetative growth will stop|
|Humidity||You should aim for an environment around 50% humidity. Over that you might get bud molding issues|
|Temperatures||Temperature levels are the same as during the vegetation stage.|
Note: Some strains will react to temperature changes differently. For example, “blue” strains will only turn blue/violet if there’s a different of at least 10°C between the day and night
PK – The two main nutrients of the Flowering Stage
The main difference with the Vegetative Stage Nutrients is the lack of Nitrogen.
Since the plant mainly uses Nitrogen in order to create new sections of the plant, now that she’s focusing on the developing her flowers there’s no need for it. For that, she’s going to need Phosphorous and Potassium, and a good amount of them.
Now just like during the vegetative stage, if you’re looking for a precise table of how much to feed your plant we can’t do so.. It depends on the type of nutrient and your strain.
Our advice is the same, follow the indications given by the manufacturer but reduce the levels a little. If your plant shows some deficiencies (apart from Nitrogen), add a little more nutrients in there.
Last but not least, don’t forget to flush your plants during the 2 last weeks of the flowering stage! If you don’t do so the buds will still be full of nutrients which will ruin their taste.. Would be too bad to waste your harvest just because you forgot to stop giving them Nutrients at the end of the cycle.
Now lets look closer to each nutrient and their use.
How does Cannabis use Phosphorus (P) during the Flowering Stage
Phosphorous basically has the same use during the Vegetative and Flowering stage, with a couple exceptions.
Once the stretch starts the plant will redirect it from the root growth to the blooming of the flowers.
Apart from that, it keeps on being part of the formation of the oils, sugars and starches and the photosynthesis process,all of which is necessary for the plant to thrive.
How does Marijuana use of Potassium (K) during the Flowering Stage
Potassium basically acts in the same way during the whole life of your Marijuana Plant.
It’s responsible mainly for 3 things during the whole life cycle:
- Encouraging the uptake of water, which your plant needs whether vegetating or flowering.
- Increasing the resistance to diseases.
- Helping the plant make better use of the light and air available.
On top of that, when Cannabis gets to the flowering stage, Potassium is essential for the development of the flowers.
Recap of PK use in Weed
|Nutrients||Use in Cannabis|
The Stretch – Final Growth and Flowering sites
What people call “the stretch” is the ~2 weeks after switching light periods, generally 18/6 to 12/12. During these 2 weeks your plant will have a very strong growth, up to 200% for the most extreme strains. You will also see the bud sites appear, starting with pistils and growing into small budlets.
By the end of the stretch your plant will have fully stopped vegetative growth and will have formed all her bud locations.
If you went for a scrog, this can also be a good time to get rid of the weak branches that don’t look too promising.
Here’s the evolution of one of our own during the stretch, as always you can click on the image to see the full version.
What are the characteristics of Marijuana’s Stretch stage:
|Stretch||What you will see|
|How to start it||Change you light pattern from 18/6 cycle to 12/12 cycles.|
|Growth||Very rapid! Depending on Sativa or Indica strains it can vary from 70% to… over 200%!|
Sativa’s grow the most during this time, so get a meter out and start measuring to max hight in your space
|Length in time||2 weeks long|
|Humidity||40% to 50%|
|Temperature||Around ~ 25°C. Be sure to measure at the level of your Apex’s!|
|Nutrients||Reduce the levels of Nitrogen given over time|
Increase the levels of Potassium and Phosphorus.
|Light cycle||12hours of light and 12 hours of night|
|Branch and leaf density|| The Apex and branches will take in high very rapidly, keep an eye out in 2 weeks time you won’t recognise her anymore!|
The leaf mass will keep growing the first half of the stretch, after which the focus will go on the buds.
Early Flowering Stage
Once your plants have finished stretching and her budlets are well formed she will solely focus on developing those buds.
You’ll see them grow and totally change during the following weeks, the closer to the harvest the denser they’re going to look 🙂
During this phase you won’t really see any trichomes, or just very few, since the glands haven’t developed yet. This is normal so no worries, within the next days/weeks you’ll see them start to come in.
Trichome Appearance and Development
A couple weeks into the flowering stage you’ll start noticing some hairy/dusty looking things on the pistils and leaves that surround them, say hello to the Trichomes!
At this point these trichomes aren’t fully formed yet and still totally clear. They don’t contain any THC nor CBD, but in time they will 🙂
For the following days and weeks she will keep on developing her buds.
On the side of the trichomes they will finish growing, developing a ball shape at their end after which, if you look through a little micro-scope, they will start turning milky and then golden/brown.
Basically, when they’re milky they contain the maximum levels of THC, after which the glands start to die and the THC is replaced by CBD.
Nutrient wise you might want to increase PK solutions a little to give her a boost, without overdoing it. This will increase her flower production, meaning bigger buds at harvest! But if you over do it she might get Nutrient burn which creates leaf mass loss, meaning less photo-synthesis which will lead to less energy, thus smaller buds, so be careful!
Stages in the development of Trichomes
|Unformed or Clear|
|Some are Clear, some are Milky|
|Mostly or all Milky|
|Mostly milky and some are turning golden/amber|
|Mostly or all golden/amber|
Late Flowering Stage
What we decided to call the “late flowering stage” starts when your pistils start to turn brown for the first time.
At this point, the flower is fully formed, you’ll have a nice and tasty smell within the room and really, you’ll just want to harvest them they look so tasty, but don’t!!
By harvesting too early you can lose up to 50% of your harvest.. which would suck, you definitely put to much effort in them no? The buds are fully formed, they haven’t finished fattening up hehe.
Marijuana pistils are known to “go brown” 2 or 3 times during the flowering stage. You’ll see the tips of the buds kind of close while the pistil dries up, totally normal. Within a couple days you will see new pistils come back out and grow, increasing the size of your buds.
Depending on the strain of cannabis, this phase can go on for a couple weeks, you’ll want to observe the evolution of the trichomes to decide when to start flushing your plants before harvest.
Pistils are not the right way to define the moment to harvest, observe the trichomes for that.
Flushing your Cannabis plants
At least 2 weeks before harvesting you want to start flushing your plants. What do we mean by flushing? At each watering from this point on you will stop giving them any nutrients.
This will force the plant to extract all the needed nutrients, like Nitrogen, from the buds and leaves in order to keep living. You might think this is counter productive, but all those nutrients in the buds will waste your harvest.
Whether it’s taste or health wise, all these nutrients need to be extracted from the flowers leaving only the cannabinoïd that are produced by your strain.
This means that while observing the Trichomes you must think ahead in order to start flushing your plants in time.
If you’re hesitating start a little earlier than later, less nutrients does mean less weight, but also tastier buds 🙂
As you can see, by the end of the flush the plant has extracted all the nutrients (especially Nitrogen, but not only) from the main leaves.
It’s not visible, but she did the same within the flowers, at the same time her trichomes are all milky and starting to brown, let’s get to harvesting!
Flowering Stage Week by Week Pictures
This section is really going to be visual and really it’s for the beauty of seeing a week by week evolution of cannabis’s flowering stage, tis soooooo pretty
We decided to share the flowering stage of our critical+ 2.0 autoflowering and fruit autoflowering strains. Just as a reminder, this was our first time messing with auto’s and they flowered waaaay to quickly. If you want to know more about all that, we did a little guide on auto flowering strains, or you can check out our past grow posts.
Alright, let’s get into it
Week 1 – Start flowering, the stretch
As we mentioned in the intro, this was our first time testing out autoflowering seeds. Found out the hard way, but they go into the flowering stage once the tap root hits the bottom of the pot… We So they flowered real while still way too small.
As you will see, during the stretch you plant will grow a LOT, depending on the strain they can grow from +50% to +200%, so make sure you get that info to chose the right time, you don’t want your buds burning on the lights ^^
Week 2 – End of the stretch
This will depend on the strains but generally the stretch is 2 weeks long. You can think of it like our teenage years, that’s when we grow a lot, have a bunch of hormones flowing and grow into our adult bodies.
You’ll know the stretch has ended because vegetative growth will have stopped and the bud sites will be formed.
Week 3 – Pistil growth and first trichomes
Now that your plant has finished her vegetative growth the development will happen around the flowers. The little pistils will start forming nice bud sites, trichomes will start growing and she’s going to start producing cannabinoids and terpenes.
The upcoming weeks are really exciting, but be careful not to jump the gun and harvest too soon! If you just take pistils into consideration, you will most likely harvest way too early and lose out on a large amount of flowers, but getting a little ahead of myself.
Week 4 – Buds thickening
4 weeks into the flowering stage the plants are really starting to have some nice flowers and smell. As you can see we’re dealing with an nitrogen deficiency on the 2 fruit autoflowering plants (left).. This is really early on for this and can’t really fight it since cannabis strongly reduces her intake of nitrogen once the flowering period has started..
Week 5 – Pistils ripening
As you can see in the middle picture, during this weeks the pistils started ripening during this week. You might think that this means it’s getting close to harvest time that would be way to hasty!
There can be 2 or 3 rounds of pistil ripening and regrowth, every time your buds get bigger. As we covered further up in the article, the indicator for harvest lies in the trichomes, not the pistils so don’t be too hasty 😉
At the end of the week we also decided to harvest the side branches of one of the 2 cheese strains since they were really suffering from a nitrogen deficiency, we figured might as wel let her focus on that main bud.
This deficiency is definitely not controlled.. although we are to start flushing the plants soon
Week 6 – Flowers closing up
During week 6 the pistils kept ripening and the flower calyx’s closed up. Although, as you can see during the week, white pistils started growing back out, starting the second round of pistil growth!
Unfortunately we don’t have any quality pictures of the trichomes but they were going from clear to milky.
Week 7 – Buds thickening & first harvest
During this week we saw the flower calyx’s start to re-open with some fresh pistil growth.
We also harvest 2 critical+ plants…. With hindsight I really think we jumped the gun and harvested waayyyy too early. We probably lost at least a third of the yield, which is really a shame since it was a great tasting flower
Harvesting the first buds
As we started saying I think we jumped the gun a bit on harvesting these, we could of probably waited a week of two, especially since we hadn’t really fully finished flushing them.. (although I can say know that it was flushed enough not to have the flavor of Nitrogen when we smoked her).
The main issue with harvesting early is loss of yield, as we covered above, cannabis buds thicken through multiple rounds of pistils growing over each other; as there is more spots from where the pistils can grow, this process is exponential, you don’t want to miss out on that last round of growth.
Here’s a couple pics of this first harvested flower
Flowering Stage of Cannabis – Frequently Asked Questions
Nitrogen Deficiency while flowering
Nitrogen deficiency can/will generally pop up at 2 moments of the flowering stage, during the stretch and the late flowering, in the first case it’s not great, the second it’s wanted.
Nitrogen deficiency during the Stretch
Since your plant is growing so much during the 2 first weeks of the flowering stage (aka the stretch) she needs a large amount of nutrients. To prevent any issues don’t hesitate to boost your NP nutrients before getting it started.
If you’ve already started the stretch things are a bit more complicated… As we’ve seen further up Cannabis reduces her intake of nitrogen once the flowering has started making it a bit touchy but not a done deal, you can
- Keep adding some Nitrogen to your feed
- Foliar feed, since it’s a mobile nutrient the plant will intake it.
- Don’t worry too much if it’s only impacting a couple bottom leaves.
Nitrogen deficiency at the end of the flowering stage
The 2 last weeks of the flowering stage having Nitrogen deficiency is positive, even wanted which is why growers flush the plants during the 2 final weeks of the flowering stage.
If you do not do this the buds won’t be as tasty, you’ll have a weird (nitrogen) taste, although it will weigh more.
Check out our other articles of the series
Couple words about the grower
This article was written by Plant Lover, Free the Tree's founder and a passionate grower of Cannabis, as well as all other plants.
Mostly from the city, I work on my computer all day so about 4 years ago, on my off time, I started growing to have some more green in my life.
I never imagined I would fall in love with botany and discover so much about this plant. Since then I keep learning everyday, meeting new awesome people of our community and grow constantly
You can always get in touch with me on our Instagram!
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