Although the home cultivation of conventional (THC) cannabis is, of course, illegal , you can grow cannabis for medical purposes (CBD varieties) at home for your own use . Growing cannabis plants, however, can be a real alchemy. So let's look together how to grow plants properly, but especially how to bring them to the flowering stage and how to take care of them further.


Flowering cannabis plants is a particularly important phase of a plant's life cycle. During flowering, hemp undergoes many changes and chemical reactions. These reactions are activated when the light conditions change, the so-called light cycle change . If the plants are given more hours of darkness, they enter the flowering phase. The length of flowering varies depending on the variety.

Male vs. female plant

During flowering, the sex of the plants is also differentiated, male and female plants are formed. After two weeks of flowering, the sex of the plants is already quite noticeable.

  • Female plants can be identified very easily, from their embryos grow small hairs , called pistils, which are designed to capture pollen from male plants. Compared to males, female plants are generally much more desirable. The reason is simple, they produce several times higher amounts of active ingredients .

  • You can recognize male plants by small balls on the stems. These balls are full of pollen. The fundamental difference between a male and a female plant lies in the fact that the male plants are not grown for their inflorescences , which are further processed, but for the pollen mentioned .

You can read more about the differences between female and male cannabis plants here .

Indoor or indoor cultivation

During indoor cultivation and subsequent flowering of hemp, it is necessary to imitate the winter / summer light conditions in a sufficiently believable manner . This process is also called "switching to a flower" . The growth phase of cannabis requires about 18 hours of light and 6 hours of darkness. However, in order to successfully start flowering, it is necessary to "switch" the plant to a 12-hour cycle, ie 12 hours of light and 12 hours of darkness .

The power of the luminosity of the lamp that you use for lighting is also very important. Good results are obtained with the use of sodium lamps. As cannabis is a plant that blooms in autumn, the lighting conditions need to be adapted. Switch to softer light from the strong lighting that mimics the summer sun. The shortened lighting cycle and sufficiently "warm" light is a perfect reproduction of the natural autumn sunshine that the plant needs during the flowering period.

Negative effects of late switching of plants to the flowering phase:

  • Plant cramping is the most common problem that can occur due to late switching. Insufficient space causes poor branching. The light cannot reach all the necessary places. The result is small and poor quality flowers.

  • The higher risk of mold is associated with crowding and mutual contact of plants. Moisture and poor temperature stick between the cannabis leaves, thus creating a suitable environment for the formation of mold.


Like late, early switching of cannabis plants can result in some negatives . Among the basic ones we can include:

  • the space intended for cultivation is not fully utilized

  • light is used uneconomically

  • about recognizing lower yields

Summary of important points about INDOOR flowering:

  • By "switching to a flower" specific chemical reactions were initiated in the plant . The first visible signs of the flowering phase appear after only a few days, usually within 7 days of the change in the light cycle.

  • the best time to "switch" is when the plants are of sufficient (or required) height .

Outdoor or outdoor cultivation

We already know that cannabis plants enter the flowering phase in autumn , that is, when the days and therefore the sunshine begin to shorten .

Growing outdoors may seem a bit easier than growing indoors , as there is no need to worry about light . Nature will arrange this for you. However, in outdoor cultivation, it is very important to choose the right seeds with an optimal flowering time, which at least corresponds at least to the climatic conditions in which hemp is grown.

In the fastest maturing varieties, in outdoor conditions, the flowering phase is between 4-6 weeks. Most commonly sold varieties begin to bloom in late July and ripen around the end of September to October.

Self-flowering varieties and flowering

Self-flowering varieties are relatively popular, as the flowering phase does not depend on specific photoperiods , which are otherwise very important in cultivation. The onset of flowering is governed by the age of the plant . If this type of cannabis is grown indoors, the lighting time is 18-20 hours for the entire "life" of the plant, while the darkness is given to the plants 4-6 hours. The plants begin to bloom about 3 weeks after germination.


Unfortunately, our climate is not entirely friendly for the trouble-free cultivation of cannabis. The biggest problem is always unwanted mold. These prevent successful harvests and significantly reduce yields. Molds most successful in confined spaces with high humidity and temperature to 15 ° C. Make sure your plants have adequate air circulation. In some cases, genetics may also be to blame.


We have already told you a lot about this topic in the previous article. Fertilization at this stage is completely different from that at the time of plant growth . The successful phase of flowering depends on a sufficient supply of quality fertilizers containing phosphorus. If you grow cannabis in a greenhouse, even the flowering time will not be possible without fertilization with a small amount of nitrogen. In contrast, growing under the open sky allows growers to phase out nitrogen fertilizers completely.

End of flowering phase and ripeness

The flowering phase ends when the plants are ripe. Knowing the optimal maturity of cannabis plants, however, is not so easy. Let's focus again on the already mentioned pistils, ie the hairs available to the female plant. These hairs are white during the growth (youngest) phase.

However, as the flowering and ripening phases of cannabis, their color changes. As the plant matures, the hairs turn brown, purple or orange . Sufficient maturity, and therefore the right moment for the harvest, occurs when the ratio of white and "colored" hairs is about 50-75% for darker colors of fists. .

The right moment for the harvest is absolutely crucial. If the flowers are allowed to ripen, they begin to wither and darken. In this case, it can be said that estimating the time of "switching" is much more banal than correctly estimating the moment of harvest. If flowering occurs, the plants die, while the late "switching" in most cases means mainly problems with the height of cannabis.

Disadvantages of early harvest include, in particular, deteriorating flower quality - imperfection and fragility . In cases where the plants are grown for seed, this is a low percentage of ripe seeds. The biggest disadvantage of early harvest is probably small yields .

Late harvesting can cause, for example, a deterioration in the taste or smell of cannabis. In the case of THC varieties (which are illegal in the Czech Republic), it is also a lower proportion of this compound, while there is an increased percentage of cannabidiol CBD, a compound that occurs in medical cannabis. CBD cannabis can be grown legally at home.

Do not forget that the cultivation, use and distribution of cannabis with a THC content higher than 0.3% is a misdemeanor or criminal offense in the Czech Republic! It can only be legally obtained on a prescription if your medical condition requires it. Respect the legislation of your state!