Photoperiod: Vegetation and flowering in cannabis plants

After germinating your seed and moving it to a more definitive space, the introduction to the light is something that is essential for us to think about. Let’s learn some more about this subject?

Like us, our plants also need light to live and thrive, for them it is even more important. Do you remember those distant biology classes? Well, we do! Plants use a process called photosynthesis to live, the process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water. With cannabis, it is no different, it needs more or less light to fulfill its vital functions.

The photoperiod is precisely the time of exposure to light,  which you or mother nature will provide to the plant. Today we will discuss this subject, bringing information about the photoperiod both in indoor and outdoor cultivation experiences.

Come with us!!!

About photoperiod and types of cannabis

In addition to being aware of the amount of light during each phase of the plant, it is also necessary to be aware of the seeds you are planting. If they are regular, whatever the strain is, during the vegetative cycle they will all look relatively similar, only during the flowering cycle will plants begin to show their sex.

But girls, what does that mean?

The vegetation comes after the seedling, this state is like the plant’s childhood and adolescence. It is time to develop, grow, develop its roots until the plants are ready to be grown ups and start producing flowers. That is why it is so important that it is in an environment with space for the roots, whether in an outdoor or indoor grow. At that moment, the priority is that she gets stronger and stays very healthy, nourished and happy.

The flowering cycle, on the other hand, is like the adult stage of the plant, and concerns the moment when your plant begins to develop pistils, which in the future will be flowers (if the plant is female) or develop stamens with pollen (if the plant is male). Each strain has a different time for its flowers to reach maturity! So, it is important that you are already preparing to harvest a lot of tasty and fragrant buds in the near future. Believe me, the little plant is preparing for the same thing! But it is also at that time that you need to pay attention to something we mentioned in the previous paragraph: the sex of your plants.

  • Typically, within the first weeks of flowering, females develop pistils, structures similar to hair.

  • Males, on the other hand, develop visible balls, as if they were bags on plants. The name of this structure is stamen and it is there that the pollen develops. In case you see both fur and cookies, you have a hermaphrodite plant. If you are male or hermaphrodite, you will have to say goodbye to the plants. Unless your goal is seed production. Yes, we’re sorry too, but it’s for your own good – and the good of your future incredible buds, since if they start seed production, much of the energy goes to that end.

  • Another important aspect is, if you planted auto-flower seeds, they will spend less time in each phase – and will bloom without depending on the photoperiod.

Now that we’ve explained this, let’s move on to the phase differences in indoor and outdoor crops.

Photoperiod in indoor cultivation

If you choose to plant indoors, you have probably seen what you will need structurally to ensure good growth of your plants. The lamps you choose are essential: they will guarantee lighting, and it is important that you choose the type that makes sense to you, thinking both of cannabis and of the energy bill at the end of the month. Last week we talked about the main differences between indoor and outdoor cultivation, and soon we will post more material focused on indoor lighting.

After which path you want to take in cultivation, it is also important to think about the lighting equation corresponding to your growth stages

The vegetative period

Cannabis reaches the vegetative state about two weeks after the seed germination.

In order to remain in the vegetative state, the plants need at least 18h of light per day. This is what allows indoor growers to keep the same mother plant for years (yes people, there are plants from many years, believe me? But you need to have a green finger like that). There are growers that recommend letting the plants receive light 24 hours a day. This can reduce your growth time by up to 30% – but it will result in a higher electricity bill.

In this phase, the ideal relative humidity is around 60-65% depending on what temperatures are achievable in the grow space. Plants want not only certain temperatures for ideal growth but also humidities because the combo is what creates what is known as the vapor pressure deficit. This is the relative relationship of the vapor pressure outside the leaf compared to inside the leaf. This vapor pressure when in ideal range allows for the plant to transpire at the highest possible rate, and in turn create the most growth energy possible all else equal. VPD Chart below.

Lower temperatures, between 20 and 24 °C, can promote more females if normal seeds are growing.

This is the phase of monitoring the growth of plants, making the necessary transplants until they reach the final pot, at least a few weeks before they start to bloom

In flowering

Normally, your cannabis plants will be ready for flowering about six weeks after the start of cultivation, but it will be up to you to change your photoperiod. As we said above, you can extend the seedling vegetative cycle if you think it can grow even more before you start to grow flowers!

Flowering usually lasts between 7 and 10 weeks for Indica and hybrid varieties, while the most dominant Sativa can take 10 to 14 weeks to fully ripen their buds. During this period, she should receive 12 hours of light and 12 hours of darkness – a 50/50 cycle.

The relative humidity of your grow needs to be reduced to 40-50% slowly as buds develop.

Ideal flowering temperatures are between 20 and 28°C.

Photoperiod in outdoor cultivation

While indoor cultivation is possible to perfectly control all conditions, we know that outdoor is a great challenge. Humidity and temperature are always up to nature; but we can schedule the planting so that the seasons coincide with the climate characteristics we seek in addition to the available light period for your plant. The ideal is to plant in the spring to harvest until autumn (in the hemisphere where you are, in this case).

Being closer to the Equator makes the regions perfect for planting all year round. This is the case in parts of northeastern Brazil, which produces a lot of cannabis, and Jamaica – a country we visited to learn more about the relationship with the herb. Imagine what beauty? Beautiful beaches, tropicality and cannabis growing all year round. Too perfect!

Thinking of the Northern and Southern Hemisphere, the farther from the equator, the shorter your season for growing your cannabis plants. That is why, in many places, people plant marijuana in a mixed way – they start indoors or in a greenhouse with supplementary lights, and take it outside to flower when weather allows. This helps to increase the time that these plants can grow!

But let’s see some interesting details here:

In vegetative

The most interesting thing is to plant your seeds in the spring. Thus, when they need light most (in the vegetative stage), summer will be approaching and they will receive what they need from the sun. On outdoor cultivation it is possible for your plants to grow at a slower pace precisely because of the limitations of the photoperiod to which they will be exposed. If you want to speed up this process, you can do this with external auxiliary lights. The ideal photoperiod, however, remains the same: 18h of light and 6h in the dark.

In the southern hemisphere, spring starts on September 22 and runs through December 21

In the northern hemisphere, spring begins between March 20 and March 21 and ends between June 22 and 23.

In the flora

As in indoor flowering, outdoor plants also need to receive less sunlight to bloom. The ideal is 12/12, that is, half the day in the light, half the day in the dark. It is likely that your plants will spend the spring and summer growing season, in the vega, and start to bloom when the temperatures cool down, in the fall. Before winter, you’ll be able to harvest your incredible buds.

Our tips:

  • In both indoor and outdoor cultivation, we advise you to germinate your seeds and transplant in the flower days of the biodynamic agriculture calendar.

  • Transplants must stop before the flora!

  • As we will talk about later, pest control also changes according to the stages of the plant. After all, in flora, you don’t want to do anything that could compromise buds, right?

  • There are people who mix the cultivation, starting outside and then taking it inside an indoor grow, or vice versa. This increases the time of the seasons and also makes it possible to have two cycles rolling at the same time – after all, everyone wants to harvest the whole year, right?

  • The indoor allows harvesting all year round because you control the photoperiod. If you are a good grower, you can make 3 to 4 harvests a year.

  • Outdoor in many countries is one harvest per year, and these are called “full term” plants.

  • Remember that haste is the enemy of perfection. Expect your plant to be very stable and healthy for the flora, to harvest the best buds.

Did we get your questions answered? Was something missing? You can ask us in the comments – we are here to help you grow beautiful and perfect buds, from healthy little plants and full of life.

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jairus butler
jairus butler
3 years ago

My entire plant turned into a flower on every stem growing on and off the main stem at stand about 3.5-4′ in height…what do I have…lmao