Cannabis flowering

December 8, 2022 0 Comments

The life cycle of cannabis is divided into several stages, the most important and beautiful one being flowering. Before it flowers, it has to sprout and get enough green mass to get ready to move on to the next stage of the life cycle. During the growing season the grower has his hands full: prune and fertilise the plants, shape them and stretch the branches so that each shoot receives an equal amount of light as a result. When the blooms begin to appear, there is less to do. The gardener only needs to maintain a comfortable microclimate and periodically water the shrubs with a nutrient solution to stimulate flowering.

Despite all this, good cannabis plant care during flowering can really boost your yield and a major mistake or misstep can ruin your plants even during the last few days of flowering. In this article we deal with the main problems during flowering, how to avoid them and how to take care of them.

The different hemp blooms

Blossoming is the developmental stage where plants form male and female flowers, pollinate and produce seeds for procreation. Cannabis is an annual plant which reproduces itself by seeds. To ensure that the population survives, it needs to go through a pollination stage every year. To do this, towards autumn, when the daylight hours are 14 hours or less, flowers begin to set on the cannabis plants. The pollen in the male flowers ripens, which will later be carried to the female flowers by the wind and insects. After pollination, the “girls” will produce seeds that will provide offspring for the following year.

An outdoor grower needs to know when cannabis plants begin to bloom and how long they last in order to know if their plants will ripen in time for the autumn chill and rains. In nature, cannabis plants adapt to the regional climate. This is why cannabis plants depend on the amount of daylight hours needed to start flowering. As soon as daylight hours are reduced to 12-14 hours, the first ovaries of buds will begin to appear.

The same applies to sativa, indica and their hybrids. The only exceptions to this are the autoflowering cannabis plants that have been artificially created by breeders based on the wild-growing ruderalis. These plants develop and enter the flowering stage irrespective of the lighting regime. The flowering mechanism is part of their genetic code and the inflorescences start to form when the plant is a certain age (usually 2-4 weeks old).

To make it clearer, we add a photo of the flowering period.

The length of the flowering period depends on the genetics of the plant. The Sativa varieties grow naturally in countries with hot tropical and equatorial climates that have long, hot summers and no cold at all. Therefore, the flowering period of such plants is quite long and can take about 2-4 months. The indica varieties, on the other hand, are naturally found in regions with a rather harsh and variable climate. In order to survive, they have adapted to develop and flower rapidly, so that the ripening period of these plants lasts no more than 1.5-2 months. The hybrid strains, which contain genetics from both cannabis strains, have a flowering period of about 1.5 to 3 months, depending on which genes they contain more of. The autoflowering varieties flower for 4 weeks to 2 months.

With indor cultivation, it is possible to control the length of the life cycle by encouraging early flowering or, on the contrary, delaying the plantation during the vegetative growth stage. To get them to flower, all you need to do is set the light regime to 14 hours or less (usually 12/12).

The flowering stages

The whole flowering period can be roughly divided into a few phases: pre-bloom, flowering itself and the maturation that follows. Each of these flowering stages is different and that means you’ll need to take different care of your plants to get the best out of them.


Pre-flowering is the growth stage when the bush begins to show the first signs of flowering. The rapidly increasing green mass ends and the bush becomes as branched and lush as possible. It can take anywhere from a few days to several weeks to finish flowering, depending on the growing conditions and genetics of the variety. Even though the shrubs are no longer as active in terms of green growth, you should not limit your nutrition to foliage fertilisation at this time. On the contrary, you should now fertilise them with nitrogen fertilisers, i.e. those used during the vegetative growth period.

Female and male inflorescence formation

During this period, the first stigma hairs will form at the nodes on the stems and will later form the base of the inflorescence. The first inflorescences often appear between the 4th and 6th node, counting from the base of the stem. These will later develop into a female inflorescence if the grower has selected feminized seeds. In the pre-bloom stage, you can already tell a ‘girl’ and a ‘boy’ from the way the blossom looks, so this is the perfect time to remove male plants that can ruin a grower’s senshi and the quality of his crop.

Many novice growers often have a problem identifying the gender of a cannabis plant. It is actually a fairly simple procedure that takes neither time nor effort, but knowledge of which only hones with experience. Males that do not belong on a plantation are usually noticeably taller than females. This is genetically conditioned so that it is easier for the falling pollen to reach the female flowers. The main difference, however, is the appearance of the setting inflorescences. Female flowers look more like microscopic bunches of bananas hanging on short stems. It is in these “bananas” that pollen will later ripen.

To give you an example, here are some photos of male and female hemp blossoms.

Female and male cannabis flowers

Once the plant is in full bloom, it redirects all its energy and resources towards producing cannabis plants with a large, resinous inflorescence. This is when you need nutrients more than ever. During this flowering time it is particularly important to provide plants with a phosphorous- and potassium-rich fertiliser. These two chemicals form the basis of any bloom complex fertilizer, irrespective of whether it is an organic or mineral fertilizer.

If they are given enough nutrients and moisture during the first couple of weeks of flowering, the grower will be able to see bigger and heavier buds at the nodes of the stalks within a month, instead of small lumps, which increase in size every day. The varieties with indica genetics will already have ceased to grow taller and the garden hybrids will have doubled in size since the start of flowering.

It is at the flowering stage that the active production of cannabinoids, oils, terpenes and other active components of cannabis begins. The spread of the characteristic cannabis aroma is linked to this. It is intensified by the terpenes, which can cause a lot of problems for household growers. So that excessively vigilant neighbours don’t cause trouble for the grower, it’s better to choose either a low-smelling cannabis strain or use a good quality charcoal filter for air purification. You can read more about such equipment on the official “Seed” forum.


When the buds have all been formed and most of the flowering is done, it’s time to start ripening. At this time, new inflorescences no longer appear, but the old ones are actively gaining volume and mass, and pouring out precious resin. Problems with the microclimate, irrigation or nutrition can rob the grower of some of the harvest or reduce its quality, so during this time you should pay extra attention to your planting.

The end of cannabis flowering can easily be determined by the appearance of the inflorescences. The trichomes on the buds, which are glands that produce resin as well as precious cannabinoids, will change colour from clear to white and then amber as the buds mature. The condition of the trichomes will also have a direct bearing on the effect the cannabis has. The predominance of milky white glands provides a more energetic and invigorating hai, while if you delay with the harvest and wait until most of the glands turn amber, the effect will be more relaxing and couching.

Stigmas, trichomes and sugary marijuana inflorescence leaves

The pistils, often called stigmas by growers, also start to change as the harvests approach. Whereas the pistils used to be dense and white or yellow-orange, as the plant matures, they tend to dry out, curl up and take on a brighter colour. When all the stigmas are dry, it’s time to start examining the condition of the trichomes in more detail to determine the ideal time for harvesting.

To get the cleanest possible effects and a pleasant taste and flavour, you should stop using fertiliser 7-10 days before harvesting and water the plants with plain, purified water. This allows all the mineral reserves in the cannabis tissue to be metabolised in time so there are no unpleasant side effects after tasting. To stimulate resin production and increase THC levels, you can immerse the plants in complete darkness a day or two before the supposed harvest date. This makes the buds even more potent and aromatic.

Hemp blooming: all the details
Setting a light regime in indoors and shortening the day out

Firstly let’s find out how to get your hemp into bloom. It’s important to know which variety you are talking about. An autoflowering cannabis plant will flower in the second, third or fourth week regardless of what the grower does. You don’t have to change the light, water or do any other tricks to get it to bloom. Photoperiod hemp needs to shorten the daylight hours. If the bushes are grown outdoors, they will start flowering in the second half of summer when daylight hours are shortened to 14 hours. How can you tell whether hemp is flowering or not yet? By the very hairs in the plant’s nodes, some will soon have grown into long-awaited buds.

In indor cultivation, the grower decides when to put the plantation into flower by controlling the light regime. He can keep the shrub in the vegetative stage longer to achieve the desired shape and size, or he can start the flowering mechanism early if the size of the room does not allow for a large, spreading shrub. The main condition is that the plant must be in perfect health when flowering starts. If there are problems with irrigation, nutrients, burns, pests or other problems, this will certainly affect the yield of the planting in the future. It is better to allow extra time during the growing season to deal with current problems and only then set up a 12/12 cycle.

There are situations where the grower has changed the lighting regime and still no flowering occurs. This is called late blooming. This could be caused by some kind of stress factor that is taking too much energy from the plant. Check whether everything is ok, whether the pH and EC are ok, whether the room temperature is ok and whether the lamps are not too close together. If everything is OK, you should probably just give the plants some more time. When you don’t have time, you can try reducing the light part of the day to 10 hours instead of 12. In a pinch, you can even put the plants in complete darkness for a day or two. This will give an extra boost to the flowering process and when the first buds appear, you can go back to the normal lighting regime.

During the flowering stage the lighting should be bright, with a predominance of the red spectrum. A lack of light will not allow the plants to reach their full potential and the yield will be poor and weak in effect. Instead of using a single bulb, it is better to install several medium-sized bulbs. In this way, the light flux will be evenly distributed throughout the room and the shrubs will not suffer from the intense heat radiated by a bright lamp. The lamps should be placed at a safe distance from the tops of the plants so as not to cause burns or hermaphroditism of the inflorescences.

The temperature for flowering cannabis varies depending on the variety (sativas are more heat-loving, indica hybrids are cold tolerant). At maturity, they are more tolerant of higher temperatures, but the heat is still an additional stress factor that can damage the shrubs. The optimum temperature is 28 °C. Strong temperature rises after lights out should also be avoided. A difference of 8-10 °C is optimal.

Humidity during flowering is also very important. If it is too damp, without active ventilation the chance of fungal or mould infestation will increase considerably. While 60-70 % humidity is the norm during the growing season, it is better to keep it at 40-50 % for flowering. Some varieties are more resistant to fungal infections, but you should not take any chances.

Watering during the flowering stage should be infrequent. Water will evaporate quickly, increasing the humidity in the room, which is an additional danger to the crop. In addition, too much water can lead to rotting of the roots and the health of the plantation as a whole.

As we’ve already mentioned, cannabis bloom fertilisers should contain higher amounts of potassium and phosphorus. They need these elements in order to produce a large and aromatic flower structure. If you don’t want to bother with a nutrient mixture, you can buy cannabis bloom complex fertiliser from specialist retailers. This already contains all the macro and micronutrients you need for healthy growth and a plants lush bloom. Fertilizing with microbial products can help to strengthen and build up the root system.

Replanting, pruning and other stressful interventions should be avoided during flowering time. Instead of using their energy to form buds, the bushes will be forced to expend their energy in recovering from the stress they have been under, which means part of the harvest will be paid back. The only exception to this would be the pruning of yellow or dead leaves, which are a burden on the plant and only draw resources from the cannabis plant.

Sometimes the resin-soaked inflorescences on the branches are too heavy and the shoots cannot take the weight and break. In this case, it is best to install additional supports or hangers to support the branches.

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