Properly switching cannabis plants from the vegetative to the flowering phase is a major step in reaching a successful harvest. There are many factors that play into when and how you should do it, each of which deserve your careful consideration. This guide should make things easier.
When you’re growing cannabis plants, there are few moments more important than the switch from the vegetative to the flowering stage. As it progresses into that final phase before harvest, your plant will make all the preparations it needs to offer you the most bud possible. In turn, making sure your plants make that transition smoothly (and at the right time) is nothing short of vital.
Plants normally do this on their own, but indoor growers have to help them along the way. It's not too difficult, but there are a few factors you should keep in mind. We'll explain all of that and more as we continue on.
What Does It Mean to Switch From Veg to Flower?
To start, let's clarify what we're talking about when we discuss the vegetative–flowering switch. See, the growth of cannabis plants is divided into four stages: the germination and seedling stages come first, followed by what we're focusing on today: the vegetative and flowering stages. The former sees the leaves and roots growing quickly to capture more sunlight and nutrients, while the latter is when the all-important buds begin to take form.
How do cannabis plants know when to do this, though? Just as they rely on the sun for energy, they also rely on it to signal the changing of seasons. As the sun sets sooner, and the plants receive less light in turn, they understand it's time to fully mature and let their buds grow.
Related article6 Tips For Improving The Density Of Cannabis Buds They don't need much help outside, but things are different when you're in a grow room where you control the light. Here, your plants depend on you shifting the light schedule to move on from the vegetative stage. As they spend less time in the light, they can begin flowering in peace. Specifically, plants need 12 hours of darkness to initiate and stay in bloom indoors.
Should You Flip the Lighting Schedule For Autoflowers Too?
It's around now when we should mention that a cannabis plant is given a label depending on whether or not it relies on this light shift to begin the flowering stage. Specifically, it's distinguished as either a photoperiod or autoflowering strain. The former does rely on a change in the light schedule, while the latter flowers according to age.
Related articleAutoflowering Versus Photoperiod Cannabis Strains
So, as you could likely guess, there isn't much benefit to flipping the lighting schedule for an autoflowering plant: They won't take too long to make that transition themselves! Most autos enter bloom after 3–4 weeks of veg.
What Factors to Take Into Account When Flipping?
Now, we wish the timing of this switch only depended on when we want our plants to start flowering, but that isn't always the case. In truth, there are a variety of factors at play, including the height of your plant, the state of its roots, the genetics it carries, and the growing techniques applied to it. We'll examine how each affects when our cannabis plants can enter the flowering stage.
Height
As mentioned, the vegetative stage is when a plant begins to climb to its potential peak height. As long as you keep it in that stage, it'll keep growing taller (up to a point), so you have to consider how much vertical space you have. Growers who let them keep climbing may find their plants bumping into the lights or ceiling and getting damaged. To avoid any potential issues, make a note of your strain's potential maximum height, and make the switch sooner rather than later if your plants are on the taller end.
Genetics
Going deeper, the maximum height of your plant is just one of many specific factors determined by its genetics. Cannabis genetics are generally split into two main categories: indica and sativa. Indica strains are usually shorter and more stout, and will grow in height by 25–50% between the beginning of flowering and harvest. Sativas, however, get quite tall, and the early flowering stage gives them time to potentially double their height. So, generally, you can leave an indica plant in the vegetative stage longer than a sativa.
As far as specific strains, you can also look up what other growers have said about the specific seeds you're growing. More than likely, lots of growers, including those selling the seeds, have reported how much time their plants spent in each stage. Get an average of all the numbers you see, and keep that in mind as you’re growing.
Robust Root Network
Along with growing leaves and getting taller, plants will also spend the vegetative stage developing a robust root network. When the roots are able to grow long without bunching up, the plant they're attached to is able to enjoy all the nutrients it needs and won't have to compromise on growth.
To ensure this network develops, you need to be sure you don't rush your plant to begin flowering before it's ready. Once the light shifts, plants will soon start focusing on bud production as opposed to root development. If they were cut off too soon, the potential of your yield is cut down in equal proportion.
There's no exact science to timing this, as you can't really go into the soil and check. The best estimate you'll be able to find is the average vegetation time for a given strain.
Easy Roots Mycorrhiza Mix View
Advanced Grow Techniques
Even if several growers are raising the same seeds in the same sort of environment, the use of certain advanced growing techniques can make one grower's ideal switch time dramatically different from another’s.
The sea of green method, also known as SOG, involves growing many short plants close to each other in a confined space, and has the explicit intent of making plants flower early. This, as it turns out, is done so each plant will develop one large cola instead of numerous small buds.
Rather than a particular time, you'll want to wait for your plants to reach around 15–30cm in height before flipping. The specific height, of course, will depend on your plant's potential maximum.
Related articleThe 5 Best Cannabis Strains For A Sea of Green (SOG) Grow
Bearing a similar acronym, but looking quite different, the screen of green growing method involves placing a mesh screen 30–60cm above the base of your plants. ScrOG facilitates proper aeration, even light exposure, and larger yields as a result.
Since you're not trying to induce flowering early with ScrOG, you'll want to wait a few weeks longer than you would when employing the SOG method.
Another fascinating method of maximising yields, lollipopping involves stripping branches of everything but the topmost growth. Proponents of this method point out how these lower sections produce small buds that waste nutrients and energy. Nobody will want to use these, so those sections are pruned to divert energy and nutrition to the buds on top.
When lollipopping, you'll want to wait for strain-dependent height milestones before you make the flowering switch. Sativas are cut off early and switched to bloom when they hit 30–45cm, while indicas can keep growing until they hit 100cm.
Good things come to those who wait, and that's especially true of those who employ the super cropping method. This strategy sees growers getting the most out of each plant, bending the upper branches down to give the lower buds more light. Along with helping those lower sections, this process also keeps the plant from getting too tall too quickly, allowing for a longer vegetative stage than average.
How to Flip From Veg to Flower Indoors
Now, with all that considered, it's time to learn how to make cannabis plants switch from the vegetative to flowering stage in the grow room.
So, during the vegetative stage, most growers keep a light schedule of 18 hours on and 6 hours off. As their plants become fully ready for the flowering stage, adjustments need to be made so they get 12 hours of darkness. This means you'll want to adjust the timer you have your light system hooked up to.
Once that's done, just keep taking care of your plants like you have, and rest assured they'll keep growing healthily throughout the flowering stage.
Switching From Veg to Flower Outdoors
Now, normally, as we brought up towards the beginning, outdoor growers won't have to worry about inducing bloom. Those who want to have a second growing cycle (or an earlier harvest), however, can still manipulate light and switch to the flowering stage sooner.
Growers can accomplish this by building a structure with a removable light-proof cover over and around the plants. If you keep them covered for 12 hours a day (after they've properly developed), you can go ahead and kiss the vegetative stage goodbye.
Be careful when trying this, though. If you aren’t consistent with your light-deprivation schedule, the extra light will make plants leave the flowering stage and go right back to the vegetative stage.
When to Flip if Plants Are Growing Unevenly
Now, say one plant has a different growing speed than the others. If you find that some of your plants are ready to leave the vegetative stage earlier, some topping and pruning may be in order. These strategies can get a plant to grow like the others, meaning all your plants can then enter the flowering stage together.
Professional Pruning Shears View
Growers should exercise these methods with discretion, as plants will offer reduced yields if stress piles up. Keep a close eye on each plant, and make sure you're not just pushing your plants to flowering for a quicker harvest. It may come quicker, but it'll be poor-quality and light, costing you more money and time in the long-run.
Can You Switch to the Flowering Phase Right After Topping?
Lastly, speaking of stress and topping, some wonder whether they should make the switch to the flowering stage right after topping their plants. Unlike most of what we've discussed here, there are different opinions depending on who you ask. To illustrate our take, we'll focus on the cannabis plant itself and consider its “feelings”.
Ultimately, the growing process is stressful in general for your plants. This stress is only heightened for a plant that goes through topping. However, the light shift and the beginning of flowering is one of the most stressful times for any plant.
Considering this, the majority of growers will tell you to wait 1–2 weeks between the end of topping and the beginning of flowering. A decent amount of growers, however, believe a plant can handle the transition with only 5–7 days of recovery. Each plant should make it to harvest in good health, but the plant that got less than a week may offer a less impressive yield. Beyond that, it's up to your time constraints and the health of your cannabis.
Steven Voser
Steven Voser is an independent cannabis journalist with over 6 years of experience writing about all things weed; how to grow it, how best to enjoy it, and the booming industry and murky legal landscape surrounding it.
FAQs
Growers can switch to the flowering stage as soon as the clone has established a solid root system. In optimal conditions, plants should be kept in their vegetative stage for approximately 60 days. This time period should give the plant the opportunity to maximise yield and acclimatise to growing conditions.
How long should cannabis veg before flowering? ›
The vegetative stage in Cannabis plants may last from 3 to 16 weeks, or even more in outdoor crops. Most growers vegetate their indoor plants for 4-8 weeks, depending on the desired plant size. Cannabis plants are usually able to start flowering from the 4th week of the vegetative stage.
How Big Should plants be before switching to flower? ›
Sativas are usually switched when they reach 30–45cm, since they grow so much during the flowering stage. Indicas are switched when they reach a height of around 100cm, giving them more time in the vegetative state.
When should I switch to 12 12 light cycle? ›
So to answer the question of when to switch from 18/6 light cycle to the 12/12 light cycle, it will be after you have accomplished your goals and tasks for the vegetative period. For most growers, this takes about 4 to 8 weeks. You can get it all done in four weeks, or take as long as eight weeks.
How long should the veg stage last? ›
So, the veg stage is when growers determine if plants are female or male, discarding any males that pop up immediately to avoid pollination. Typically, plants will show their sex around the 6-week mark for reference. All in all, the veg cannabis growth stage typically lasts anywhere from 4-8 weeks.
How do you know when the vegetative stage is over? ›
You can tell when the vegetative stage has ended because the plant starts growing sex-specific flowers in addition to leaves and vegetative growth. For example, you know the flowering stage has started when the plant starts growing pistils/white hairs/buds if plant is a girl, and balls/pollen sacs if a boy.
Does longer veg time increase yield? ›
The longer you keep your plants in the vegetative stage, the bigger your plant will be, resulting in bigger yields from plants that were vegetated longer.
Should you flush cannabis when switching from veg to flower? ›
Cleansing cannabis of old nutrients is a good way to reset soil while a plant is transitioning into a new stage of growth. Think of this as a preventative flush. It's not required, but by the time a plant reaches the flowering stage, it has sucked all the nutrients from the soil and could benefit from a fresh start.
Can cannabis be in vegetative stage too long? ›
Photoperiod cannabis plants kept in the vegetative stage will continue to grow. So if you veg them for too long and don't control it, they will grow very large and unwieldy. Some strains of cannabis like to grow tall and spindly—for instance, landrace sativas.
How many nodes should I have before flowering? ›
It is recommended that you wait until your plants have at least four nodes before topping them, and most growers recommend topping the plant above the sixth node. Nodes are the part of a plant that connects new stem offshoots with older growth, which can form a branch, a leaf, or in the case of cannabis plants, a bud.
Generally, you want to water every 2 or 3 days during Flower and you want to water enough that 10-20% of water comes out from the pot as runoff. You can check your soil moisture by sticking a finger in the pot: if the soil is dry a couple inches down, then it is time to water again.
Can you flower too early? ›
There is really only one disadvantage. If your weed flowers earlier than intended, your weed plant will be smaller than it could be. In other words, there is a reason for such a growth phase. From the grower's point of view the purpose of the growth phase is to be able to harvest as much weed as possible at the end.
Will buds grow without fan leaves? ›
It won't have a negative effect on the flowering process — in fact, if you fail to properly prune and/or remove the fan leaves, the flowering process is much more likely to go awry. Once your plant has entered the flowering stage, you'll want to execute another round of defoliation.
How long after switching to flower do buds appear? ›
So in summary, you will not see buds for the first three weeks. During the third week, pre-flower sites will emerge, but will not fill in until Week 4.
How far should light be during flowering? ›
Once the vegetative stage is complete, plants enter the bloom or “flowering” stage. For established plants, they are already where they need to be in order to thrive. During the flowering stage LED Grow lights should be located between 16-36 inches from the plant canopy.
Is 4 weeks veg enough? ›
Most cultivators vegetate their plants for 4–8 weeks. After this time, a switch to 12 hours of light per day is required to initiate flowering. In contrast, autoflowering plants flower on their own.
How do you fatten up buds before harvesting? ›
To some degree, more light translates to fatter buds and higher yields (you'll need to pay attention to the distance between your grow light and plants or your plant may suffer from light burn). Increasing light intensity is the most effective way to fatten up buds.
How many times should you defoliate veg? ›
Ideally, we recommend defoliating your plants once during veg and once during flower. If you're an inexperienced grower, only defoliate once during veg. If you are more experienced, you may want to try defoliating multiple times (given your grow schedule allows enough time for plants to recover after each defoliation).
Can you make a full recovery from a vegetative state? ›
Any recovery from a vegetative state is unlikely after 1 month if the cause was anything other than a head injury. If the cause was a head injury, recovery is unlikely after 12 months. However, a few people improve over a period of months or years.
What should my buds look like at 5 weeks? ›
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.
Some people recover from a vegetative state, but it is usually not a complete recovery. The brain damage will likely result in permanent disabilities. Recovery is most likely if the cause of the vegetative state is an injury or a reversible condition such as low blood sugar or a drug overdose.
How do you maximize yield in flowering? ›
During flowering, switch the lighting schedule to 12 hours on and 12 hours off. The key for maximum yields is to provide large amounts of light and to distribute it as evenly as possible across the canopy. Space your lights accordingly.
Does more light equal more yield? ›
Light Intensity and Yields
The light intensity rule of thumb is that a 1% increase in light equals to a 1% percent increase in yield. In a study by Wageninen University, they discovered this to be true of all horticultural crops they evaluated including, fruiting (vine) crops and flowers.
How many times can you top in veg? ›
Some experienced growers will top up to 5 times (or more) to obtain 32 branches and can be well rewarded for their efforts. 2. Healthy plants usually take 2-3 days to recover from topping. After topping, do not remove the leaves from that node as these are needed to power growth of the branches from that node.
What week of flowering do buds smell? ›
Late flowering / Ripening stage – week 6 to harvest
In the last few weeks, buds gain the most weight. They are sticky to the touch and can be very smelly.
Do buds grow during flushing? ›
Plants, however, do not stop growing when they are being flushed. Rapidly expanding buds can be seen even while the flush is removing nutrients.
How often do you fertilize in flowering stage? ›
The nutrient requirements will change dramatically when the plants enter the flowering stage, and this may be a little hard for new growers. You can feed your plants 1-2 times every week, gradually increasing the nutrients, but at the same time pay attention to your plants' reactions after each feeding.
How long does it take cannabis to recover from Fimming? ›
Precisely when to FIM is at the grower's discretion. Take note plants will need about 1 week to recover and for the new growth to develop. Expect an ugly sight in the aftermath. A set of torn leaves if you pinch and a Medusa head of colas are typical.
Should I defoliate during vegetative stage? ›
Vegetative phase
We recommend defoliating vegging plants just before you switch them to bloom: Start by removing big, hand-sized fan leaves first. These tend to overshadow almost anything below them, making it hard for light to properly penetrate your plant's canopy.
Can you skip vegetative stage? ›
Instead of having to wait out a full vegetative cycle plus a full flowering cycle, these growers can skip the vegetative phase all together and harvest their buds much sooner.
The answer is simple and lies in the biological makeup of the cannabis plant. Cannabis plants will flower when they receive more than 12 hours of continuous darkness. This is known as a short-day plant.
When should I trim off fan leaves? ›
Usually, growers trim the fan leaves weeks before harvest, which is a period that leads to senescence, a phase in the plant cycle when the larger leaves start fading away. It is safe to start removing these dying leaves and continue until harvest.
What stage do buds grow the most? ›
Buds typically grow the most toward the end of the flowering life cycle. You probably won't notice much budding out at the beginning of the flowering stage, and it will slow down toward the end of the cycle, when buds become fully formed. Once buds have reached full maturation, it's time to harvest your marijuana.
Can you overwater during flowering? ›
We all grow up knowing plants need soil, sunlight and water, but we often don't realize the importance of consistently watering flowers. A lack of moisture can cause a flower garden to wilt and produce very few – if any – blooms. Overwatering flowers can cause disease and the drowning of plants.
Do you trim fan leaves during flowering? ›
You can remove fan leaves during flowering in much the same way you do during veg. Prune away large leaves that are overshadowing bud sites, as well as dead or dying fan leaves. One thing to keep in mind is that you should prune in intervals, giving at least a couple weeks between each session.
Should I feed during flowering? ›
Flowering – 5-20-5 or 5-25-10 – During flowering, you want to prioritize phosphorous to promote bud growth and make sure to limit nitrogen so your plant doesn't get too tall or “leggy.” You want it to concentrate on developing huge buds, not lots of stems or leaves, and phosphorus will make your buds grow.
What week Do plants stop stretching in flower? ›
Once the initial hormonal changes from the onset of bloom have finished your cannabis plant should stop stretching. Usually, some 2-3 weeks after bloom began.
Do plants need more water during flowering? ›
Watering during the flowering period
During the pre-flowering and early flowering stage, the plants don't require additional watering. However, once the plants enter the peak flowering stage, the buds start sucking the soil dry. The buds are filled with water; it's logical that more watering is required.
Which can induce early flowering? ›
Drought stress induces early flowering under LD conditions and delays flowering under SD conditions in Col-0 (but not in Ler) of Arabidopsis (Riboni et al., 2013). Expression of the flowering gene FLOWERING LOCUS T (FT) is involved in both stress-induced flowering and photoperiodic flowering, as discussed below.
Should I remove yellow leaves during flowering? ›
They are essential to photosynthesis. Removing all the yellow leaves is not recommended surgery, especially for young plants. Correct identification of the source of the problem and swift remedial action can restore marijuana. Senescence is when plants will naturally yellow off and die.
The Room Must Be Dark
The ideal drying room must be dark, as light can damage the THC in your buds. While it does not hurt to have a light source inside to check on the progress of your buds, you should keep it off most of the time, and block all other passages of light that can enter the room.
Can buds grow without sugar leaves? ›
If you choose to dry prune the buds, the sugar leaves can protect the buds. Not all cannabis has sugar leaves, though, and whether yours does depends on the strain. If you don't want your plants to grow sugar leaves just avoid strains that do.
How tall should you be before switching to flower? ›
This method typically involves a height-based flowering switch. Sativas are usually switched when they reach 30–45cm, since they grow so much during the flowering stage. Indicas are switched when they reach a height of around 100cm, giving them more time in the vegetative state.
Can I harvest my buds early? ›
Harvesting at the right time is crucial when it comes to growing cannabis. If you harvest too early, you will have premature buds which leads to a poor product and a smaller yield. Harvest too late and the potency of your weed takes a steep decline or turns to rot.
What does pre flowering look like? ›
The female pre-flower will look like a fuzzy female flower, but with only two white or pink fuzzy pistils growing from the node of the plant. It is best to wait to induce flowering to your plants before the pre-flowers appear and this will help eliminate the male plants from your crop before flowering.
What happens when buds are too close to light? ›
Cannabis plants will show a number of key signs when they're getting too much light. The most obvious indicator is leaf burning. This typically causes yellow leaves at the top of the plant directly under the grow lights. While the inside veins stay green, the leaves take on a yellow, burnt look.
What is the best temperature for flowering stage? ›
Manipulate temperature and humidity
In the flowering stage, temperatures in 65- to 80-degree range are ideal. At night, most plants prefer temperatures between 68 and 75 degrees Fahrenheit. Colors like pink and purple come out when nighttime temperatures are at the low end of the scale.
Do LED lights shorten flowering time? ›
Faster flowering can result in significant savings and better profitability for plant breeders. Various conditions can affect the flowering speed, but the quality of the light spectrum is probably the most important.
Should I remove fan leaves during vegetative stage? ›
Should you remove fan leaves? Yes, removing or pruning some fan leaves is a necessary step when cultivating cannabis healthy plants. When fan leaves become too large or abundant, they block the light and airflow to parts of the plant that can hinder trichome and cannabinoid production.
Can I remove large fan leaves during flowering? ›
You can remove fan leaves during flowering in much the same way you do during veg. Prune away large leaves that are overshadowing bud sites, as well as dead or dying fan leaves. One thing to keep in mind is that you should prune in intervals, giving at least a couple weeks between each session.
Yes you should – but with the correct technique. A proper thinning will remove 20-40% of the mid to upper foliage every 5-7 days. Removing these fan leaves opens up light and produces better air exchange to the lower canopy.
Should I prune during flowering stage? ›
Pruning during flowering should be extremely light and limited. One example of appropriate pruning would be the removal of fan leaves that are shading healthy bud sites. The pruning of damaged, diseased, or dead plant tissue can be carried out throughout both the vegetative and flowering cycles.
What week Do buds get fat? ›
Week 5: Buds Grow More and More
Cannabis plants get fatter and fatter every day. This is a good sign that the plant is in full flowering mode. The odor will be very strong at this point. Some of the plant's white pistil hairs may turn into a darker amber or brownish color.
What week Do buds get sticky? ›
Late flowering / Ripening stage – week 6 to harvest
They are sticky to the touch and can be very smelly. You are very close to reaching your goal = harvesting! Most importantly, buds are now covered in trichomes, which are rich glandules for secreting THC and other cannabinoids.
What week Do buds get the biggest? ›
The last three weeks is when your buds can actually gain the most weight – that is if you feed them Overdrive®. After your peak bloom phase, your plants enter their late bloom phase (the precise timing and length of which depends on the strain of cannabis you're growing).
How much should I water during flowering stage? ›
Generally, you want to water every 2 or 3 days during Flower and you want to water enough that 10-20% of water comes out from the pot as runoff. You can check your soil moisture by sticking a finger in the pot: if the soil is dry a couple inches down, then it is time to water again.
