The Flowering Stage Of Cannabis Week By Week
Slip-ups during the flowering phase can significantly affect the size and quality of your harvest. With a few simple tricks, however, you’re guaranteed a great harvest every time.
- 1. The first few flowering weeks
- 2. Week 1 (transition stage and stretch)
- 3. Week 2
- 4. Week 3
- 5. Week 4
- 6. Week 5
- 7. Weeks 6, 7 and 8 (late flowering stage, right before harvest)
- 8. Pro tips for a better harvest
- 1. The first few flowering weeks
- 2. Week 1 (transition stage and stretch)
- 3. Week 2
- 4. Week 3
- 5. Week 4
- 6. Week 5
- 7. Weeks 6, 7 and 8 (late flowering stage, right before harvest)
- 8. Pro tips for a better harvest
When the light cycle provides your cannabis plants with longer hours of uninterrupted darkness, they enter the flowering stage. Your plants will stop growing and instead put their energy into producing buds (flowers). Outdoors, this will normally happen when the days get shorter around the end of summer. When you grow indoors, flowering will begin once you switch your lights to 10-12 hours of darkness.
For most cannabis strains, the flowering period will last about 7-9 weeks, although some sativas require even longer for their buds to mature.
What happens during flowering and at what exact time can somewhat vary depending on the particular strain you are growing. So don’t expect your plants to follow this schedule to the T; see it more as a general guideline that you can go by. Let us look at the flowering phase of cannabis week by week.
THE FIRST FEW FLOWERING WEEKS (WEEKS 1, 2 AND 3)
When the flowering period starts, it isn’t an abrupt change in your plants’ growth. Cannabis won’t just stop growing and then go into flowering right away. In these first weeks of flowering, many cannabis strains may indeed undergo a considerable growth stretch. This is important to know when it comes to feeding your plants properly, but also if you want to give them sufficient space to grow.
|(Week 1)||(Week 2)||(Week 3)|
WEEK 1 (TRANSITION STAGE AND STRETCH)
In the very first weeks of flowering, your cannabis plants will be in the transition stage. Thinking that winter is not far away and that she will soon have to carry a big load of bud, your plant will likely grow rapidly. Some strains can almost double in height during this time. Because of the fast growth that your plant is undergoing now, this early flowering phase is also known as the stretch phase.
While your plant is putting in quite some overtime to gain size and height, she will grow a number of new leaves mostly at the top of the main colas. Your cannabis plant is busy growing “green stuff,” like leaves and stems so she can become stronger and sturdier.
Important things to know in this early stage of flowering.
Although your plant has officially entered the flowering phase, she will now have an increased need for growing nutrients. You should not abruptly change your nutrient schedule and use flowering nutrients from one day to the next. It is usually recommended that you continue to give growing nutrients for at least one more week once flowering starts.
With the stretching of cannabis in early flowering, you may possibly want to think about training techniques such as low stress training (LST). This is where you bend the stems down and away from the centre of the plant so you can get an even canopy for a more efficient use of your grow lights. This can help you obtain much better yields later on.
In week 2 of flowering, you may spot the first white pistils growing on your female cannabis plants. These fine and wispy white hairs will develop at those locations where the big fan leaves meet the main stem. It is these fine hairs that will later become buds.
If your cannabis plant happens to be a male, it won’t grow these “hairs,” but will instead grow small pollen sacs. Should you grow regular, non-feminized plants where you don’t know their gender, now is the time when you should “sex” your plants so you can separate the males from the females. The males won’t grow buds and will also pollinate your females, causing them to grow seeds. This is something you do not want to happen.
To properly feed your plants once they start to flower and to initiate the first signs of growing buds, you should check your nutrient manufacturer’s schedule. It is normally around this time at week 2 where you will have to increase flowering nutrients to help your plants reach their maximum yield potential.
Your cannabis plants have still not entirely stopped growing and will now be about 50% bigger than what they were just three weeks earlier. Although still stretching a bit, the stretch will now gradually slow down and soon come to a complete halt.
At the locations on the plant where you previously saw some hairs, you can now see the first signs of real buds developing. There still won’t be many resin glands and trichomes on your plants, which means that the smell won’t be too pungent yet either.
This phase of flowering where your plant is starting to spend increasingly more energy on growing flowers is particularly critical. Make sure that the nutrients you give are appropriate and check the labels for the recommended dosages.
As your plants become more picky, you should check for potential deficiencies that could manifest in various ways, such as discoloured, yellowing leaves or loss of leaves entirely. At the same time, you should also check your plants for signs of possible overfeeding (“nutrient burn”) that could show up around this time as well. Nutrient burn will usually show in the tips of the leaves becoming discoloured. If this happens, you need to cut down on feeding.
|(Week 4)||(Week 5)|
At week 4 of the flowering stage, your cannabis plants will likely have stopped growing altogether and are now spending all their energy on growing buds. There will still be white hairs sticking out from the buds, but the buds themselves will become bigger and fatter with each day. With more and larger buds growing, your plants will now produce more trichomes, making the odour a lot more noticeable at this stage.
Since your cannabis plant will have stopped growing, you won’t have to pay attention to training your plants any longer. Where you bent down branches before, now you may possibly consider holding them up should they require structural support.
In week 5 of flowering, you can observe the buds all over your plant becoming thicker. You may also spot new buds growing in new places such as along the main cola. With buds abounding, your cannabis plants will get fatter every day. This is a surefire sign you are in full flowering mode. At this point, your plant will have a very intensive odour. Ensure that you have a good ventilation system in place if you grow indoors or in a region that doesn’t allow for legal cultivation.
Some of your cannabis plants’ previously white pistil hairs may now be turning darker into a brownish or amber colour. At the same time, when you check the trichomes of your plant, you may spot some of them becoming opaque. The trichomes becoming milky white and the hairs turning darker are all signs of your plants not being too far from harvest.
|(Week 6)||(Week 7)||(Week 8)|
WEEKS 6, 7 AND 8 (LATE FLOWERING STAGE, RIGHT BEFORE HARVEST)
Not all cannabis strains require the same amount of time for their flowering, but many varieties will be ready to harvest in these last three weeks. There are, however, not too many strains that will be ready before week 8.
Flushing Your Cannabis Plants
Depending on the flowering time of your particular strain, the time for flushing your cannabis plant is normally two weeks before harvest. When you “flush,” you stop administering nutrients and give the plant only plain, pH-balanced water in these final weeks. This will get rid of (flush out) salts and minerals in the soil which will make for a better and more pure-tasting bud. Otherwise, your smoke will be quite harsh and can have an unpleasant, chemical taste.
Check Your Plants For The Right Harvest Time
To find out when it’s time to harvest your plant, you can use a jeweller’s loupe or a small microscope to regularly check your plants’ trichomes. You can observe whether the trichomes turn from clear to a milky white colour. If many of the trichomes you see are still clear and transparent, it means it’s still too early for harvest. But when most of the trichomes have an amber colour and an opaque clarity, this means that the THC content of the buds is at its maximum and the plant is ready for harvest.
PRO TIPS FOR A BETTER HARVEST
Guiding cannabis plants through their flowering phase can be intimidating, especially for rookie growers. Follow these simple tips to ensure you always end up with a great harvest:
• SEXING YOUR PLANTS
Most growers identify the sex of their plants in the final week of vegging or the early weeks of flowering. Remember, males develop pollen sacs that look like small balls, and need to be culled or separated from your females if you want to avoid them getting pollinated.
Also, keep an eye on your female plants as they flower to catch any hermaphrodites. While it’s not common, some cannabis plants may develop both female and male flowers, while others may develop stamen (colloquially known as “bananas”) as a final attempt to create seeds in response to heavy stress.
• FIX PROBLEMS BEFORE FLOWERING
If you’re an indoor grower, you have the advantage of controlling when your plants start to flower. Make sure to use this to your advantage and only ever flip your plants to flowering when they’re 100% healthy. You don’t want to be correcting nutrient deficiencies or fighting pests and diseases while your plants are budding.
If you’re growing outdoors, you have less control over when your plants start to flower. Instead, you’ll want to pay close attention to the calendar and fix any issues before the end of summer.
• MAKE THE TRANSITION INTO FLOWERING AS SMOOTH AS POSSIBLE
Flowering plants require different humidity levels and temperatures than vegging plants. Rather than changing the temperature, humidity, and light cycle at the same time, we recommend gradually changing the temperature and humidity over two days, then letting your plants grow accustomed to these changes by leaving them in veg for just a few extra days before flipping your lights.
• GET YOUR LIGHTING RIGHT
Cannabis plants like red and orange wavelengths during flowering (between 580–700nm) to encourage the ripening of their flowers. For best results, use a grow light with this spectrum during the bloom phase.
• DON’T TRANSPLANT CLOSE TO BLOOM
Transplanting shocks your cannabis plants. Always avoid transplanting right before or during the flowering phase to avoid damaging your yield potential.
• TRIM EXCESS FOLIAGE
Before flowering, make sure to train and trim your cannabis plants a bit to allow as much light as possible to reach its bud sites. Now, every grower has their own approach to trimming, but we like Kyle Kushman’s recommendation: “If the tip of a branch doesn’t break at least 50% of the height of the plant, it’s gone”. The idea here is to help your plant concentrate its energy only on the bud sites that’ll produce the best product.
Also, remember to always trim yellow or dead foliage during flowering. While your plants should stay lush and green up until about week four, some of their foliage will stop thriving as they devote more energy to bud production. This is completely normal, and you can safely remove any leaves that turn yellow or dry out completely.
• KEEP HUMIDITY AT 45%
Bud rot is a serious issue that can ruin an entire harvest. To protect your plants and optimise their growth, keep the relative humidity of your grow room at 45%.
• CLOSELY MONITOR TEMPERATURE
Flowering cannabis plants like daytime temperatures of 20–23°C and nighttime temperatures of around 15–18°C. Make sure to watch out for sudden drops or spikes in temperature when you turn your lights on/off. Sudden drops can shock your plants, while sudden rises can cause condensation to form on the surfaces of your buds, leading to bud rot.
• USE A CARBON-FILTERED AIRFLOW SYSTEM
Supplementing with CO₂ during the bloom phase can enhance growth and yield. If you can, aim to keep CO₂ levels at 1,000–1,200ppm during flowering.
• AVOID NUTRIENT BURN
You can’t compensate for nutrient burn during flowering. Make sure to follow a strict feeding calendar and remember to stop feeding two weeks before harvest and flush your plants.
• SUPPORT HEAVY BUDS
It’s not uncommon for flowering plants to buckle under the weight of their buds. Use bamboo stakes and string to support heavily loaded branches and ensure they get as much light as possible.
• AVOID LIGHT BURN
Like with nutrient burn, you can’t compensate for light burn during flowering. Remember to keep your lights a good distance from the top of your canopy. Light burn not only damages healthy foliage but can cause calcium deficiencies in the early flowering phase. If the tops of your plants start to bleach during flowering, it’s likely you need to lift your lights!
• USE FULVIC ACID DURING PREFLOWERING
Using fulvic acid in the late veg/early bloom phase can help increase the size of your buds early on. Also, remember to give your plants more calcium during bloom in both hydro and soil setups.
Growing weed can seem complicated and challenging. Cannabis plants, after all, are sensitive, and a single slip-up during the bloom phase can significantly impact the size and quality of your yield. To guarantee a great harvest every time, remember to bookmark this guide to the flowering phase and read it over before you flip the lights on your next batch of plants!
Watching your cannabis plants flower is both exciting and daunting. Click here for an in-depth overview on how to guide your plants through the bloom phase.
7 Unfortunate Plant Training Mistakes
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Did you know that “training” your cannabis plants to grow many main bud sites (instead of just one) is a simple and free way to get bigger yields indoors? Plant training can increase indoor yields by 40% or more (compared to letting plants grow naturally) by forcing plants to grow bigger, denser buds, without as many smaller or airy ones.
In the vegetative stage, marijuana plants are trained to grow wide and flat, like a table
In the flowering stage, this shape ensures that many bud sites develop into long, thick colas by taking advantage of the fact that cannabis plants put the most energy into buds that are both at the top of the plant and close to the grow light.
Although plant training can produce impressive results, sometimes marijuana growers aren’t given the right information, which can cause unfortunate mistakes that hurt their yields!
With that in mind, I will cover the 7 most common marijuana plant training mistakes, so you get the yields results you want every time, even if it’s your first time!
1.) Not Training at All
In our growing forum, when I asked what people’s biggest mistakes were when it came to training their cannabis plants, the most common answer was actually growers regretted not training their plants at all!
It’s true that you can get great results without any plant training, but training techniques can significantly improve your yields compared to letting the plant grow into its natural shape. Plant training can be as simple or as complex as you want it to be, but even a little bit of effort in your plant’s early life can make a big difference to your final bud weight!
The trained plant on the right had many more main colas and produced far more bud than the untrained plant on the left, even though it took up less space
2.) Breaking a Main Stem by Accident
It’s important to use bending techniques from the beginning of a plant’s life because stems start getting stiff as they get older. Starting while the plant is still young makes the whole process go much more easily!
However, even if you’re careful, it can be easy to snap a stem by accident. This most often happens when trying to forcefully bend an older stem that has become thick and unyielding.
Nothing is better than bending when stems are flexible to get your plants to grow exactly how you want, but there are a few techniques that can help you bend over stems after they’ve already hardened!
Prevent broken stems by bending at the newest growth if possible, where stems are more flexible.
Supercropping (Advanced) – If a stem feels too stiff but it must be bent, don’t force it! Use a technique called “supercropping” to soften up the inside first, so the skin doesn’t break.
- Pinch the stem tightly between your fingers at the place you want it to bend
- Start gently wiggling the stem back and forth while also trying to crush the new joint in between your fingers.
- Wiggle back and forth for 10+ seconds, or until the stem has greatly loosened up at the place you want to bend.
- Once the stem feels loose and flexible at the joint, you’re safe to bend it over and secure it in place. This can even work with thicker stems if you’re patient enough to wiggle for a while!
If you do end up breaking a main stem, you can often tape up the injury like a cast and the plant will heal itself over the next week or two.
Remember: If you do break off a main stem early in a plant’s life, it’s no big deal because there are usually dozens more growth tips to take its place! And even if you break off a main stem/cola during the flowering stage and can’t tape it up in time, it can help to remember that most growers lose a cola at some point!
3.) Mistakenly Keeping Plants Too Small
A very small plant just can’t make as much bud as a bigger plant, so keeping plants smaller than needed can reduce your yields. You will get the best yields by growing your plants so that they fill up your grow space.
Since this plant was kept so small before it started flowering, it just doesn’t have the size or infrastructure to support a lot of buds. There’s nothing a grower can do at this point to get a plant like this to yield a lot of bud. It’s important to avoid mistakenly keeping plants too small before they start making buds!
It’s important to wait until a plant is at least 3-4 weeks old before initiating the flowering stage (putting cannabis plants on a 12/12 light schedule), even if you’re trying to get to harvest as fast as possible.
This is because a plant won’t start flowering before about week 3-4 anyway, so giving plants a 12/12 light schedule before that time just reduces the total amount of light they get each day, and they won’t get as big as plants under 18/6 or a 24/0 schedule from seed.
3-4 Week Old Plant – Never switch to 12/12 earlier than this or plants will stay tiny, and waiting a few more weeks is probably better!
This plant was switched to flowering when it was 4 weeks old, and yielded about an ounce in one big cola.
Some growers recommend you wait until 6 weeks to start flowering. One reason is that cannabis plants tend to mature the fastest if they have already started showing “pre-flowers” (tiny versions of adult flowers) before initiating the flowering stage.
But the main reason is that letting the plants go just a little bit longer – to about week 6 – will give you plants that are significantly bigger and which can support bigger buds.
6-Week Old Plant That’s Been Trained to Grow Flat
After being switched to 12/12 immediately after the above picture, the plant turned into this, yielding about 6 ounces on the single plant. Two extra weeks in the vegetative stage can make a huge difference in plant size!
Note: These rules don’t apply to auto-flowering plants, which will automatically start flowering on their own without any input from you. If you want a very small plant that yields a lot, consider auto-flowering strains: they’re ready to harvest about 3 months from germination and stay small on their own! Overall, it’s much better than doing 12/12 from seed.
4.) Letting Plants Get Too Big
As we just covered, if you have the space/height for it, you’ll get better yields for your electricity by giving the plant time to get to a decent size before switching to the flowering stage.
However, if you let a plant get too big during the vegetative stage, it may completely overgrow your space!
Look at how this plant has already grown into the grow lights in the vegetative stage! This is a problem because the lights can’t be lifted up any higher in this particular grow space, and the plant is going to double in height after the switch to 12/12! This kind of crazy overgrowth can happen before you know it if you have a fast-growing plant, so stay aware of how big your plant is getting!
If plants are allowed to get too big during the vegetative stage, you’ll not only end up wasting time and electricity, you’ll also find yourself with an overcrowded grow space. Plants being too close to each other and the grow lights can cause light burn, white powdery mildew, bud rot, and other unwanted problems.
Flowering Stretch: It’s important to remember that plants often double in height (known as the “flowering stretch”) after the switch to the flowering stage, so it’s important to change to 12/12 around the time the plants have reached half the final desired height.
Pre-Stretch – Right before the switch to 12/12
Post-Stretch – 4 weeks after the switch to 12/12. Notice how much taller they got!
If you have a plant that’s been growing incredibly tall and lanky, with a lot of upward growth without as much side branching, consider that a plant like that may stretch up to three times its height after the switch to 12/12. A plant that tends to grow short and bushy its whole life may not stretch much at all.
Different strains will stretch a different amount after the switch to 12/12. The main clue is what the breeder says about the strain, as well as how the plant tended to grow in the vegetative stage (lanky vegetative plants often become lanky adults).
5.) Topping Plant Early or Incorrectly
Removing the top of the main stem (“topping” the plant) before it has grown at least 3-4 nodes often wastes more time than it saves.
In fact, removing any part of the plant when it’s very young can stunt the plant, meaning it may grow slowly or stop growing altogether for days or even weeks.
However, if you wait until a plant is healthy and growing fast with a good root system, it won’t even slow down after being topped! Waiting until the plant is the right size often improves your overall results from topping.
These young cannabis plants are ready to be topped
If you cut off just the very tip of your plant, there’s very little chance of stunting, even if it only has 3 or 4 nodes in total.
Many growers top down to the 3rd node/pair of leaves (like in the following picture) in order to form a short manifold. If you plan on any kind of extensive training like building a manifold, wait until the young plant has grown at least 6 nodes before starting; this ensures it has established a good root system. The more of the plant you remove at a time, the more it stresses the plant, so you want to make sure your plant is mature/strong enough to handle it!
Be careful not to damage the growth tips during topping. These tiny stems will become your new main colas, and the base of every growth tip is where buds form.
Always leave a little extra stem when topping a marijuana plant – this helps prevent the main stalk from splitting!
6.) Not Securing Your Plant Properly!
Don’t use string or anything “sharp” to secure plants, as it can start cutting into their skin over time! Also, it’s important to make sure that you can easily access all your plants after training.
Never use string to hold down your plants!
Notice how this plant can’t be moved from its location because it’s attached to a nearby wall? Don’t do this! Always attach your plant directly to the pot so you can pick it up and move it. Also, avoid using something sharp like string or chicken wire to hold down the plants, because it will slowly cut into the plant’s “skin” over time and cause damage.
Plant twist ties are perfect for securing plants! They bend into the shape you want, and are soft enough they won’t hurt plants.
Or get creative! Any type of soft flexible wire works well
Make sure to attach any twisty ties directly to the plant container; this lets you pick up and move the plant freely!
As the plant grows, whenever some of the colas are getting taller than the others…
Bend the tallest ones over until they’re all the same height as each other. Following just that one principle will produce the shape you’re looking for!
7.) Excessive Training on Sick or Slow-Growing Plants
When a cannabis plant is slow-growing or suffering from deficiencies, it is much more sensitive to stress from training. Things like topping, supercropping and extreme defoliation can all aggravate a sick plant and make it take longer to recover.
If you have a sick or slow-growing plant it’s good to give them a few days of TLC before you commence training 🙂
Always let sick plants recover before extensive training. This plant suffered from a grower accidentally giving 3x the correct amount of nutrients. It’s important to wait until it’s healthy and growing new leaves every day before doing anything else to this poor plant!
What can you do to help a cannabis plant relax for a few days?
Help plants recover quickly by moving the grow light a few inches away, and leaving the plant alone on an 18/6 light schedule (if it’s in the vegetative stage, of course, if you have a plant on a 12/12 light schedule you don’t want to change it!).
Providing relatively low levels of light in a comfortable, temperate environment without any disturbance can help a stressed plant regain its strength and start growing fast again in just a day or two. Once your plant is healthy and growing again, put the lights back on at full strength!
After extensive wilting from a heat spell, the grower of the plant below thought his baby was a goner. He tossed the dying plant in a bucket at the edge of his grow room, with the plan of throwing it in the garbage later that day. He somehow forgot, and a few days later he came back to find out that the comfortable temperature outside the grow tent and filtered light levels from a nearby window had been just the thing to bring the plant back to life! Even with just an inch of water at the bottom of the bucket, the plant was thriving!
At a recent growing convention in San Diego I heard from another grower who’d noticed that lowering the light levels just a tiny bit can help a sick plant recover more quickly. The worst thing you can do for a sick plant is turn up the light, because it makes the plant work harder to keep up with all that photosynthesis!
I thought a cannabis plant could come back from anything?
When people say, “It grows like a weed” and explain how cannabis plants can recover from anything, they’re talking about a healthy, fast-growing plant. You really can do almost anything to a vibrant cannabis plant in the vegetative stage and it’ll bounce right back!
For growers who always have healthy plants, it can seem like plants simply can’t get stunted. But if you take the same approach with a sick, sparse or slow-growing plant, it can dramatically slow down the plant’s growth for days or even weeks in rare cases!
Now is not the time to train this plant (or try anything new really). Wait until it has recovered first, then start training!
Whenever you’re thinking about training or removing parts of the plant, always consider the plant’s overall health first. You’ll know when you would be better served by waiting a few days to start training.
Now that you know how to prevent the 7 most common plant training problems that hurt yields…
Training your plant to grow many big buds (instead of just one) can increase your yields dramatically! Learn how to avoid the most common mistakes…