After about 4-6 weeks of growth, the cannabis plants show in advance which sex they have. This is called pre-flowering. Small flowers with threads form directly at the leaf base of the stem, if it is a female plant. The pre-bloom recedes after a few days and is not yet the actual flower. It gives experienced growers the opportunity to determine the sex of the plant within a few days before the actual flowering phase. From this point on, the plant is sexually mature.
During the growing phase, the cannabis plants grow quite fast after a certain point and form many leaves and side branches. The stem becomes thicker and the plants grow taller and bushier.
Then one day you will notice that the plants not only grow vertically, but new leaves also form in the leaf axes. The time has now also come for the plants to receive more light and thus energy, which they convert into the formation of strong lateral branches. This phase within the growth phase is also called the secondary growth phase.
After a few more weeks of the secondary growth phase, the cannabis plants will look even bushier and have more internodes. Now the cannabis plant will also reach sexual maturity and show its sex. How long this takes depends on the cannabis strain. Normally, it takes between 4 and 8 weeks for the pre-bloom to show. With some sativa varieties, it can take considerably longer.
As a grower, you should now optimise the growroom accordingly, reposition and repot the plants for their new phase of life, which they are now entering.
Pre-flowering and recognising the sex
At pre-flowering, cannabis plants show their gender as mentioned above. Every cannabis gardener hopes at this point to get as many female plants as possible, if Regular Seeds were used, otherwise the sex is clear anyway and only female plants will be used. Pre-flowering occurs in the leaf axils. At the end of the growth phase, you should check the plants daily to see if there are any flowers in the leaf axils. You can also use a magnifying glass or microscope for this, because at the beginning the buds are very small and sometimes difficult to see. Pay particular attention to the interrnodes on the trunk and then also check the side branches. As a rule, the first pre-bloom appears in an internode on the trunk.
male pre-bloom female pre-bloom
If you can't see and find any pre-blooms now, it means that your plants are not yet sexually mature. You just have to wait longer. The pre-bloom and also the flower will come when it is time. To find out the sex of your plants, you can find exact information here: Male, female, hermaphrodite.
When should I initiate flowering?
In this phase of pre-bloom, the plants stay for one to two weeks. During this time, new growth zones form and the growth form of the plants begins to change. Pre-flowering is a sign that the plants are "adult" enough to start flowering. The grower can now decide whether to send his plants into flowering now or to continue the growth phase.
It is even possible to keep cannabis plants alive for up to 12 years by giving them enough light and taking good care of them. Plants with a very long growing period (3 months and more) develop into huge, bushy cannabis trees in many cases. These plants first grow to a certain height and then become a sprawling bush. Often, at some point, the large plant stops producing new side shoots and only concentrates on producing leaves to replace dead ones with new ones.
By not sending the plants into flowering immediately with the pre-bloom, but keeping them in the growth phase for some more time, you end up with bigger and more vigorous plants, which accordingly can simply yield much bigger buds.
However, many growers send their plants into flower earlier to speed up the development process and get a quicker harvest.
When a plant is in the 4th week of the growing phase, showing its sex or coming into pre-bloom, you can leave it a few more weeks in the growing phase to allow the plant to form even more side branches and leaves. Later, when the plant flowers, this extra branching will result in more and larger flowers and an optimal result. It should be kept in mind that if canabis plants stay longer in the growing phase and are grown larger, there should also be enough space available, because the plants will in most cases stretch again considerably during flowering (up to 2-3 times as much) and will then push a small grow box to its limits in no time at all.
Flower production depends on the growing environment, the genetics of the cannabis strain and the amount of leaf buds. All leaf buds are potential bud areas 😀 The amount of buds is set by genetics, the extent to which this is fully utilised or not depends on the external environmental conditions.
If cannabis plants are to be sent into flowering early (i.e. at the beginning of pre-flowering and when they are still rather small), then correspondingly more plants must be cultivated on the same growing space in order to use it to its full capacity. It comes to somewhat the same yield whether you fill the grow room with many small plants or only 2-3 large ones. Due to the shorter development time of the smaller plants, more buds are produced per year. However, this presupposes a complete utilisation of the grow room, three small flowering plants in one corner of the grow room will of course never deliver the m² yield that is specified for one variety. A complete flower carpet in the box is necessary!
Keeping these things in mind makes it easier to decide whether to do a short or long growing season.
How do I initiate the flowering?
Very simple: Reduce the lighting time from 18 hours a day to only 12 hours a day. The cannabis plants will then start to flower by themselves at some point due to the light change or the changed lighting duration.
The 12-hour lighting at 12 hours of darkness per day is an absolutely necessary condition for nomalperiod cannabis plants (all cannabis plants except automatics) to develop flowers and produce good results as intended. The 12-hour lighting should always start at the same time. Please don't experiment and change the lighting, the ladies don't like that at all and they will take revenge with poor yields and hermiting. Therefore, use a timer so that it runs like clockwork!
What happens if I send cannabis plants into flower before pre-bloom?
I would advise you not to. Problems can arise when cannabis plants are sent into flower before pre-flowering. The plant panics, you could say, gets terribly stressed, thinks it has missed something, and gets upset, the result is:
- Stress-related sexual problems (hermaphrodites, hermaphroditism)
- abnormal bud growth
The best harvest results will always be achieved by waiting until the cannabis plants have reached pre-bloom before sending them into flower.
Mothers that are to be preserved for many years are usually lit continuously for 24 hours. This way there is less risk of the plants being blocked in growth by pre-blooming or slowly degrading.
Flowering for cannabis
If all has gone well and you have taken good care of your plants, they will now move into the flowering phase. The male plants will be removed from the grow room at this stage, provided regular seeds have been used and the males have not already been sorted out by pre-bloom.
During the strict 12/12 lighting cycle, the plants fill up more and more. They develop more side shoots and leaves. The solar sails further down stretch to their maximum size so that they get the greatest amount of light possible. The plant starts to produce more and more flowers and I call it becoming more rounded 😀 if you know what I mean.
The flowers of the cannabis plant keep growing as far as they are not fertilised and then also constantly produce THC. THC is an oily, resinous substance that is produced in the trichomes.
In the peak phase of flowering, the calyxes swell more and more and become increasingly covered in resin. The hairs start to change colour and change from a white, light colour to an orange colour, depending on the strain. Each cannabis strain is different, but usually, white hairs turn reddish and reddish hairs turn brown.
- It is extremely important that cannabis plants in the flowering phase really do not get any light during the 12-hour dark period and stand in absolute darkness. There must also be no light pollution due to light shining in from outside or from the home. This can severely disturb the plants in their flower production and even cause a flowering plant to go back into the growing phase. The blossoms then begin to "fade", literally regress and no longer grow properly.
- The flowering times given by seed banks can only be a guide and are not accurate to the day. Each plant is unique in its genetics and therefore the exact flowering time has to be determined by observing the plant and buds. If the conditions are not optimal, the total development time and flowering time of the plants may be prolonged.
- Flowering times of cannabis strains can vary greatly, from as little as 6 weeks for the fast indicas to 20 weeks for some sativas (e.g. many hazes).
- Towards the end of the flowering period, the large leaves of cannabis plants often turn yellowish or die. This is completely normal and has to do with the fact that the plant now only cares about flower production and with the switch to flower fertiliser, the growth of the leaves is no longer promoted and "fed", but rather the flowers. This is how it should be. At the end of the flowering period, the plant prepares to end its life cycle and puts all its energy into the flowers.
- In the last weeks of the flowering period, when the flowers are getting bigger, special care must be taken to ensure that the humidity in the grow room is not too high and that no mould (botrytis) develops in the buds. Biological plant protection products such as Botrybel help to prevent mould. Furthermore, the use of sufficiently strong ventilation is self-evident, especially important in this phase to avoid too high humidity. In addition, one or better several ventilators and swivel fans should be directed at the flowers so that they are well ventilated. Never spray the blossoms with water or other liquids, as this can cause botrytis to develop extremely quickly and endanger the entire harvest. You can find more about proper ventilation at Climate control in the grow room.
- During the flowering phase, cannabis plants undergo an explosion of flower development 2-3 times. Each time, the flowers swell more and their volume increases significantly. The first flower explosion usually occurs after about 4 weeks of flowering, the second after about 8 weeks. Again, this depends on the cannabis strain. With experience and time, you will get an eye for when a cannabis plant is ripe. You can read more about this here: Maturity in cannabis plants.
