There are lots of things the beginner grower needs to know before they decide to start their own marijuana-growing project. And the time when to switch cannabis to the flowering mode is one of the questions that is essential not only for the newbies but many experienced growers as well.
In many sources, you can find the information that a certain strain starts flowering at week 8 or 10. If you start pushing your plants to change the mode regardless of other circumstances, you may risk getting a very unimpressive amount of yield. Why is it so, you may ask, if it is already time for “spring,” the plant just has to follow its nature? The thing is, it is not so easy. Let us explain.
When it comes to an indoor garden, it is the grower who manages “the weather” and “times of the year.” You garden does not depend on the light day and rainy weather, but it depends on your growing style, the air in your grow room, the light regime, and of course, on the strain you have chosen.
It is useless to know in advance which exact day you need to switch from the veg mode to the flowering mode if your plants do not look the same.
The clones that looked pretty much the same when you started to root them can develop drastically differently. The difference in growth can have a number of reasons, from its position under the light bulb to the tiny, unnoticable scratches on the leaves or stem. The myriad of factors can make two previously identical-looking clones turn into absolutely not similar to each other plants.
Counting weeks with seeds can also be a bit confusing. Some growers refer to week 1 as one week from the moment the seeds germinate from the ground, while others prefer to start counting from the moment the first set of leaves appear. You can also hear the growers start counting weeks only after the young seedling is transplanted (whenever it happens). So when you read “the instruction to the strain” how can you know what exactly the author meant?
At this point, the number of weeks of the vegetative growth has little help to a grower. You cannot treat all the plants the same way. Obviously, you cannot give the same treatment to a 3-weeks-old seedling that is barely 4 inches tall and a 3-weeks-old clone that has grown over two feet tall. You need to find some other, wiser way to decide when it is the proper time for switching the light.
Plant height is a more universal and objective way of understanding whether the plant is ready for flowering or not yet. If you know exactly how tall the strain you chose might be by this moment, it can be a nice indicator of when you should change the light regime.
A plant’s height is measured from the level of growing medium to the very top of the stem (not the leaves). Apart from the strain's standards, you should also deduce the maximum height of the plant according to your room size and your lighting system.
Most people put aside one of the rooms in the residential homes for their future garden, so we are talking about 8-foot ceilings. But it can also be attics, grow tents, or garages, so the room sizes can be really different.
What is universal in this case is the distance between the top of your plant and the light bulb. High-Pressure Sodium (HPS) and Metal Halide (MH) grow lights provide a lot of heat that can not only burn the leaves but even start a fire if the plant is too close. Remember to keep a distance of at lease 12 inches between the lighting setup and your garden.
If you use LED lighting, which is more heat-friendly but more expensive, then you can shorten the distance between the leaves and light bulb up to 4 inches.
If it is possible, the best option would be to install adjustable lighting, so you can provide maximum light to every plant whatever size it has.
The moment of switching your 18 24 hour lighting regime of vegetation to a 12 hour flowering regime also depends on the strain you have chosen. Try to find out everything you can about your strain. But even if you have very little information, knowing whether it is indica, sativa, or hybrid can give you an idea of how to treat this plant and when to switch to another mode.
After switching to a 12/12 light cycle, indica strains start to slow their growth. You may expect the plant to add about 25-50 percent of its total height, and mostly it will grow only during the first two weeks of the flower mode.
So, if you have, for instance, a 2 foot tall indica plant, you can expect it to finish growing at 3 feet.
Sativa strains are more unpredictable in their growth. After switching to the flowering mode, they continue growing, sometimes becoming up to three times taller than by the end of the veg stage. So, for instance, a 12 inch sativa may become about 36 inches tall (or even taller) after switching to a 12/12 light cycle.
That is the reason why sativas are usually not recommended for beginner growers who want to have an indoor garden.
When it comes to hybrid strains, you can find out their maximum height only experimentally. Some of them tend to grow more like indica, while others are similar to sativas. In any case, when you grow a hybrid strain for the first time, you had better expect it to double its size after changing the mode.
This point would be essential only for experienced growers, as for the newbies we would recommend first to grow the plants as simply as it is possible. But those who have already mastered different growing styles might have noticed that it also influences the time for switching to flowering mode.
If you use the Sea of Green method, it is recommended to wait till the plants (usually, indica-dominant) reach 6 12 inches in height.
With the Screen of Green method, plants usually stay several weeks longer in their vegetative growth and are recommended to switch to the flowering mode not sooner than one week after the tops are bent down.
The Lollipopping method requires the grower to remove the lower branches and leaves of the plant right before switching to the flowering mode. The plant height might be 3 feet for indica strains and about 1.5 feet for sativa-dominants.
The Super Cropping method is one of the most complicated ones, but it helps receive the biggest yield with a minimal number of plants. The veg period in this case goes much longer as you bend down the stem to prevent the plant's vertical growth and stimulate the growth of lower branches. You may switch the light mode when the plants fill all your horizontal space.
Apart from everything written above, there is one thing you should take care of before switching your plants to the flowering mode. Keep your marijuana garden healthy. Weak and damaged plants can rarely provide you a nice (if any at all) yield, they simply do not have enough strength for flowering. So care for your garden nicely, and the reward will come.