The cannabis flowering stage is when plants shift from producing leaves, side branches and roots to developing buds, making it one of the most important phases of the entire grow cycle. Many growers are unsure when flowering actually begins, what changes to expect each week, and how to tell when plants are ready for harvest.
This week-by-week guide explains how the flowering stage typically progresses, what visual signs to look for, and how timing can vary between different strains and growing environments.
By understanding these stages, growers can better support healthy bud development and avoid common mistakes. The sections below break the flowering process down into clear, manageable weeks and will allow you to become an expert of the flowering stage!
Key Takeaways
- Ideal temperatures range between 65-75°F (18-24°C).
- Humidity should decrease from 70% at the start to 40-50%
- Cannabis plants require high light intensity and PAR
- Plants will stretch once the timer has been switched to 12/12
- Autos do not require a specific light cycle to flower
- Plants stop stretching from week 4 and focus on flowering
- During the stretch, plants can double or triple in size
- Pistils will be visible during week 2 of the flowering period
- Trichomes will develop on the buds and leaves from week 4 onwards
- Using a magnification tool is necessary to examine trichomes
- The final 2 weeks of the flowering stage are when only water is used
- Flushing helps improve the flavour, and produces a clean smoke
What is the cannabis flowering stage?
The cannabis flowering stage is when your plant switches from vegetative growth to producing buds. Outdoor cannabis plants are triggered as daylight hours decrease around August time, whilst indoors it is triggered by changing to a 12/12 light cycle. It’s a crucial stage because the buds are the part of the plant that is rich in cannabinoids like THC, and the reason why most of us grow.
Without a successful flowering stage, your plant may not yield very much, or what it does yield could be poor quality, so it's vital to take extra care of your plants during this time and know what to expect week by week
What is the duration of the cannabis flowering stage?
The flowering stage lasts 8-13 weeks depending on genetics. Indica cannabis plants require 7-8 weeks, sativas are closer to 11-13 weeks, and hybrids sit in the middle requiring 8-10 weeks. Autoflower strains can be as short as 6 weeks with the average flowering time from seed to harvest needed 11-13 weeks. This varies based on the strain type, with sativa dominant strains usually taking the longest. The end of the flowering stage is dictated by trichome ripeness, with most growers picking the point of peak potency to harvest.
What are the 6 keys to a successful flowering stage
- Avoid Stress: Maintain a stable environment. Drastic changes in light, temperature, or humidity can stress plants, hampering bud development.
- Optimize Nutrients: Switch to bloom nutrients rich in phosphorus and potassium. Too much nitrogen can reduce bud growth.
- Monitor Temperature and Humidity: Ideal temperatures range between 65-80°F (18-26°C). Humidity should decrease progressively from 40-70% at the start to 40-50% at the end of flowering.
- Check for Pests and Disease: Regularly inspect plants. Remove any affected areas promptly to prevent spread. Use organic pest controls if needed.
- Time Your Harvest: Harvest too early, and the buds won't be as potent. Too late, and THC may start to degrade. Look for when most trichomes are milky, and pistils are dark for the best results
- Light Intensity: Cannabis plants require optimal levels of photosynthetically active radiation (PAR) in order to produce resin rich buds and sugar leaves.
Pre-Flowering & First Signs of flowering stage
There are different factors to consider when looking for early signs of the flowering stage in your plants. If you are growing autoflowers, this doesn’t really apply as autoflowering varieties are pre-programmed to enter the flowering stage automatically, regardless of external factors. Autos have a short vegetative period of 4 weeks. Before flowering is induced regardless of the light cycle.
Photoperiod plants on the other hand begin to show their first preflowers one or two weeks after the lights have been flipped to 12/12, and they have stretched towards the light, significantly increasing internal spacing. in size The initial preflowers will look like little white whiskers that are called pistils. This is the first sign of the bud developing and that the plant is female
First signs of flowering stage outdoors
Growing outdoors, you are entirely reliant on mother nature to do all the work. With no control over the light cycle your cannabis plants will only begin to develop their preflowers once daylight drops below around thirteen hours of light.
This is why if you are growing outdoors it is important to plan your grows according to the weather in your region. Ideally, you want to time it so that your plants are ready to be harvested before winter arrives, increasing the chance of mold In the northern Hemisphere this normally means you will be harvesting your weed between September and November.
The first signs of the flowering stage to look out for will be exactly the same whether growing indoors or outdoors. You will notice the plants stretch and grow taller, with white hairs developing at the nodes of the stem and side branches.
So once the light begins to dip usually around August time onwards, keep an eye out for those pistils we mentioned and you know the flowering stage has begun.
What do buds look like when they start to form?
Early bud development begins with those little white pistils and gradually develops into a cannabis flower. Around the nodes where the pistils are growing from you, you will begin to notice the development of some small tear shaped growth, these are called bracts and are the first signs of the actual bud developing.
It is important not to confuse the early signs of a female flower with a male pollen sac. Pollen sacs on male plants will produce flowers at the nodes.
If a male plant is growing among your crop the pollen sacs could flower and open up spreading pollen into the air. This results in pollinating the female plants and ruining your crop, as the female plant will now be fertilized and produce cannabis seeds instead of those beautiful frosty buds we want to harvest and smoke.
Read our guide on sexing your cannabis plants and how to spot the early signs of male plants to avoid this mishap.
If you want to avoid the risk of male plants altogether, the best option is to grow using feminized cannabis seeds. These seeds are selectively bred so that nearly 100% of them grow into female plants, eliminating the chance of developing pollen sacs and preventing accidental pollination.
Feminized seeds give growers far more control and consistency, making them ideal for anyone focused on producing high-quality buds without the extra work of identifying and removing males. They are also extremely practical for home growers and eliminate the need to remove plants once flowering is induced.
Week 1 of the 8 week Flowering Stage – The flip
Once a cannabis plant is exposed to a 12/12 light cycle indoors, they will produce auxins and hormones in order to stretch as tall as possible, become bushy and start focusing on bud development.
A hormone called phytochrome (PR), is a pigment found inside cannabis plants that is responsible for the plant shifting from vegetative growth to flower. The same hormone is actually suppressed as soon as seeds germinate.
critical levels of PR are activated and after about 5 days in this state, plants receive the signal to switch over to the flowering stage. This process is known to many growers as ‘the flip’and will determine how tall your plants will become.
If you are concerned about tall plants or are limited in height indoors, then you should consider LST. The Low-stress training (LST) techniques are ideal for controlling the height, shape and structure of your plants.
- Cannabis plants produce auxins and hormones to initiate flowering
- They will begin to stretch causing increased internodal spacing
- At this stage, it is difficult to see any pistils developing between the nodes
- Lights on and off temperatures range between 65-75°F (18-24°C).
- Relative humidity levels need to lower from 75% down to 50%
Actionable Tip: Use LST during the stretch phase to control height and improve light distribution.
Week 2 – First signs of flowering
Around the second week after flipping (or approximately week no. 4 with autoflowers), little white whiskers known as pistils begin to emerge from the nodes and fan leaves protrude from the plant’s main stem.
These sites are known as bud sites and will be the spot to watch for emerging buds. Should your plant produce sacs instead of pistils, that means you have males in the garden, and you should get rid of them ASAP to avoid developing seeds and to maximize flower production. If your plant produces white pistils and male flowers, then you will have a hermaphrodite and should be removed from your grow space.
While the plant focuses its energy on bud production at this stage, that doesn’t mean the rest of the plant has stopped growing. In fact, by the end of week 3 of flowering your plants are likely to double or treble in size since the flip. Pistil development will be increased, and by the end of week 2, your plant will have 1 cm-long pistils growing at every internode.
- Plants will continue stretching and can double or treble in height
- Pistils will be forming and are easy to see
- The size of the pistils will be close to 1cm long
- Lights on and off temperatures range between 65-75°F (18-24°C).
- Relative humidity levels should be 50%
Actionable Tip: Remove male or hermaphrodite plants immediately to prevent seed formation.
Week 3 – Buds begin to develop
At this stage your cannabis plants won't have completely stopped stretching and your plants could be up to 200% bigger than they were prior to flipping the lights.
Side branches and leaves become more apparent in week three of flowering and more pistils can be seen emerging from the nodes. Plants are still stretching at this point and are still quite flexible, so if you haven’t done LST yet, this is still a good opportunity to work on that flat canopy, which if you are growing a high yield marijuana strain can increase your yields by as much as 60%.
This is also when you should start paying attention to leaf tips and watch for any nutrient imbalances, signs of discolouration or burnt tips (nutrient burn) that could stunt your plants’ growth. At this stage plants will have time to recover from any potential nutrient issues, though the earlier you spot them, the easier it will be for your plants to recover and grow healthy and robust.
- The plants will now be 200% their original size since vegetation
- You should be feeding a mild nutrient solution such as 2ml per litre
- Pistils will now be much larger and have a white fuzzy appearance
- Lights on and off temperatures range between 65-75°F (18-24°C).
- Relative humidity levels should be 50%
Actionable Tip: Monitor leaf tips closely and correct nutrient issues early to avoid stunted growth.
Week 4 – Stretching has stopped
One month into flowering, vegetative growth will have more or less stopped, which means plants will put their energy into flower production. Those mini buds will start to get bigger by the day, and you will also notice some sparkly little trichomes appearing on bud sites and the smaller leaves.
However, along with increased capitate trichomes comes increased odor, so ensuring that you have a top quality carbon filter in your grow space will keep odours away. This particularly applies to indoor stealth grows where privacy and security are top concerns.
By the end of week 4, you will notice your plants are now fully stretched. The pistils will have a sharp pointed appearance forming in clusters. Now is a good time to transition to a PK feed as cannabis plants depend on optimal amounts of phosphorus and potassium during flowering.
- Relative humidity levels should be 50%
- Plants will have reached their final height and will not stretch any taller
- Trichomes will become visible on the small bracts connected to the pistils
- Nutrients high in P and K can be increased to aid in flower development
- Lights on and off temperatures range between 65-75°F (18-24°C).
Actionable Tip: Increase phosphorus and potassium feeding once stretching stops to support bud development.
Week 5 – Trichomes begin to ripen
At the halfway point of the flowering stage, your plants should be displaying easily recognizable buds with an abundance of white pistils, and some pistils may have shifted colour to orange or brown. Trichome covered buds will also begin to form along the main cola and along the side branches.
It is during the 5th week of flowering that buds will start to swell up and stack together. and pack on some serious size. Staking your plants' side branches with gardening canes or bamboo canes is well advised to help maintain the structure and provide support during pinnacle flower development.
When using a magnification tool, you will notice that trichomes may start becoming cloudy/milky at this point, and this is also an indication of increased terpene production. This also means your garden is going to become aromatic and pungent,
Around this time is when growers should start thinking about reducing nutrients and boosters., Harvest time is only a matter of a few weeks away and many growers will want to flush their gardens for a week or two before harvest.
Of course this is based on a fast flowering strain, however leaving the final 2 weeks of 12/12 for flushing plants with plain pH adjusted water ensures a smooth, flavour filled product and clean smoke.
- The buds will be well developed and be covered in trichomes
- Terpene production will be high causing a strong aroma
- Staking the side branches using canes helps support heavy buds
- Lights on and off temperatures range between 65-75°F (18-24°C).
- Relative humidity levels should be 50%
Actionable Tip: Support heavy branches with stakes to prevent breakage as buds gain weight.
Week 6 – Start checking your trichomes
Bud growth continues in week 6 and some pistils start to darken, and some leaves begin to yellow and wilt, mostly fan leaves. You will notice the bracts now appear frosty, swollen and dense with a tear shaped structure coated in trichomes.
Many leaves will be naturally defoliated (from wilting, for example), however larger fan leaves, especially the older ones towards the bottom of the plant, can be removed once discolouration is noticed as the plant by now is using other parts for photosynthesis.This is because the plants have used up all the available nitrogen.
Other yellowing leaves that aren’t receiving much light, particularly those closer to the base of the plant, can also be removed to provide better air circulation. This will also redirect the plants’ energy from providing leaves with nutrients to full-on bud production.
- Relative humidity levels should be 50%
- A magnification tool should be used to examine the trichomes closely
- The colour of the trichomes will shift from clear to milky and cloudy
- Older fan leaves will turn yellow and brittle and can be removed
- Lights on and off temperatures range between 65-75°F (18-24°C).
Actionable Tip: Use a magnifying tool to track trichome development and plan your harvest window.
Week 7 – Start flushing your cannabis plants
It is from this point onwards you will cut off all nutrients and give the plants only water. The reason being that you want to encourage the plants to use up their internal nutrient reserve, whilst washing undissolved nutrient salts away from the roots and growing medium. Your plant's leaves will now begin to display seasonal colours ranging from purple, yellow, red and magenta.
At week 7, you will only have 2 more weeks left and buds should be pretty thick and well developed. Buds will have, with swollen calyxes, orange-brownish pistils, and erect trichomes that should now contain a small ratio some amber-coloured caps filled with resin.
These amber trichomes should make up around 10-15% of the mature trichomes visible on buds, the rest being mostly cloudy/milky. Once you reach this level of maturity, you can start counting down the days to the final chop.
Anything above 40-50% amber trichomes on the plant means that your flowers are overripe, and you can expect a very couchlock inducing effect. If you decide to chop without many amber trichomes, the effect will tend to be more cerebral.
- Check the buds for signs of mold and cut away and remove moldy buds
- Only pH adjusted water is given to plants to flush them of nutrients
- Leaves will start to shift in colour indicating nutrients are being used up
- Trichomes will be close to mature and there will be 10-20% amber
- Lights on and off temperatures range between 65-75°F (18-24°C).
- Relative humidity levels should be 45-50%
Actionable Tip: Flush plants with pH-adjusted water to improve final flavour and burn quality.
Week 8 – Peak Ripeness & Harvest
Peak ripeness is reached towards the end of week 8. This is where plants are most colourful as by now most of the leaves should have turned red or yellow and the milky and/or amber trichomes fluoresce. If you are waiting for the right moment to take some photos of your grow, plants will be the most photogenic around this time, so dust off that camera and snap away.
You will continue to feed only water and allow the plants to make one final push at ripening and bud development being perfect. The pistils during the final week will be 80-90% orange or brown and the buds will have a hard to squeeze density.
Cannabinoid and terpene levels are also at their highest here, so if you want to retain as much as possible, best not to wait around much longer and give your girls the chop. In addition to peak cannabinoid levels, your plants will also be at their most pungent. You can start preparing your drying room and getting everything you need ready to make the harvesting part as smooth as possible.
- Plants should be cut down and placed in a temperature controlled dry room
- Plants will be ready to chop down after a full 14 day flush
- Lights on and off temperatures range between 65-75°F (18-24°C).
- Relative humidity levels should be 45-50%
- Check the buds for signs of mold and cut away and remove moldy buds
Actionable Tip: Harvest when most trichomes are milky with some amber for peak potency.
Summary
Growing buds is an incredibly rewarding experience, to the point where you want to keep doing it again and again. Each week there is something to pay attention to and seeing flowers develop and flourish in real time is an exciting process in and of itself.
With time and practice, you will be able to manage your plants at each stage of flowering so that you get a big fat (and gorgeous) harvest without breaking a sweat.
Now that you’ve harvested your plants, you can move on to the next important phase, trimming, drying, and curing. You’ve gotten this far, just a few more steps and you can enjoy the flowers of your labor. Good luck becoming a wizard during the flowering period and harvesting cup winning crops every time!
Happy growing!
