When to Switch Weed Plants from Growth to Flowering

If you grow cannabis plants, you know that there are a number of important moments. One of them is the switch from the vegetative phase to flowering time. For your plants, the finish line is coming into view. In this transition phase, they make all the necessary preparations to develop as many buds as possible. It is therefore imperative that you make this transition (at the right time) as smooth as possible. Normally plants do this themselves. However, if you are growing indoors you will have to give them a helping hand. It’s not higher math, but you do need to take a number of factors into account. In this article we explain everything.

What does switching from growth to flowering mean?

First of all, it’s good to know what the vegetative stage and flowering stage entails. You can divide the growth of cannabis plants into 4 phases. Plants first germinate and then reach the seedling phase. This is followed by the vegetative phase and flowering period, which we will focus on in this article. During the vegetative phase, the emphasis is on the rapid development of leaves and roots. This allows plants to absorb as much light and nutrients as possible. The flowering stage revolves around the production of those oh-so-important buds. But how do cannabis plants know when to do this? Plants rely on the sun for energy, but the sun also signals seasonal changes. When the days shorten, plants receive less light. They understand that the time for ripening has arrived and start producing buds. Outdoors, cannabis plants require little help. But if you’re growing in a grow room, it’s a completely different story. Here plants rely on you to adjust the light schedule to enforce flowering time. As the number of light hours decreases, they can gradually begin to flower. Indoors, plants require 12 hours of darkness to induce and maintain flowering.

Should you change the light schedule with autoflowering strains?

It is important to mention that we distinguish between certain cannabis plants. In fact, some cannabis plants do not depend on a change in light to induce flowering. We divide them into photoperiodic and autoflowering strains. The former depends on a change in light schedule, while the latter blooms based on age. You probably understand that it doesn’t make much sense to change your light schedule for autoflowering plants. These varieties make the transition on their own. Most autoflowers switch to flowering after a 3-4 week vegetative phase.

What factors should you consider?

In a perfect world, you switch your plants to the flowering phase when you want them to. Unfortunately, this moment depends on several factors. Think about the height of your plants, the state of the root network, the genes and the cultivation techniques used. Let’s examine how these factors affect your plants as they enter the flowering stage.


As mentioned, cannabis plants try to reach their peak during the vegetative phase. As long as you keep them in this phase, they will grow taller and taller (up to a certain height). It is important to take vertical space into account. If you leave this out, your plants may end up colliding with the ceiling or the grow light, leading to damage. Avoid problems and take into account the maximum height of your strains. With taller plants it is better to switch to flowering earlier.


The maximum height of your cannabis plants is just one of the many factors that are determined by genes. In general, we divide cannabis genes into 2 main categories: indica and sativa. Indicas tend to stay smaller and fuller. Between flowering and harvest, height increases by about 25-50%. Sativas can be quite large. Due to their early flowering they can easily double in height. In general, you can vegetate an indica longer than a sativa. As far as specific strains are concerned, it makes sense to read experiences from other growers. Many growers, but also sellers of seeds, are happy to provide you with this information. It pays to know how much time plants spend in the various stages. Take the average of all these numbers and keep this in mind during your growing process.

A well-developed root network

Vegetative plants are busy not only growing bigger and developing leaves but also producing a complex and strong root network. When roots have the chance to grow freely in length without accumulation, the plant is able to absorb all the necessary nutrients. This guarantees an optimal growth process. To ensure that this network develops properly, it is wise not to start the flowering period too early. As soon as the light changes, plants focus on the production of buds and no longer on the root system. Wake up flowering too early and you reduce the potential yield. This is difficult to time, since you can’t see into the soil. Make a good estimate by using the average vegetative period for your chosen strains. Easy Roots Mycorrhiza Mix (10) View

Advanced Cultivation Techniques

When different growers grow the same seeds in a similar environment, the timing of switching can still vary considerably. This is due to the use of certain advanced growing techniques. The following are some of these techniques.

  • Sea of Green (SOG)

The Sea of Green method, also known as SOG, revolves around growing many small plants together in a small space. The goal is to induce an early flowering. Each plant develops one large cola rather than several small buds. You do not determine the flowering time in advance, but you wait until the plants are 15-30cm tall. However, the specific height depends on the possible maximum height of your plant.

  • Screen of Green (ScrOG)

The abbreviation is similar to the previous method, but the technique is quite different. In ScrOG, you hang a wire mesh 30-60cm above the base of your plants. ScrOG improves aeration and light exposure. A higher final yield is the result. ScrOG is not about inducing flowering early. Wait a few weeks longer than you would with the SOG method.

  • Lollipopping

Another fascinating way to maximize your yield is lollipopping, or thinning. In this process, you remove all lower plant growth. Proponents of this technique point out that the lower branches hardly produce any buds. The plants waste nutrients and energy. No one is waiting for small, airy buds. By pruning away the lower branches, plants put all the energy and nutrients into the higher buds. When lollipopping it is important to wait until your plant reaches a certain height before switching to flowering. This depends on your chosen strains. Sativas flower earlier, at a height of 30-45cm. Indicas can be as high as 100cm when you make the switch.

  • Supercropping

Patience is a virtue and this is especially important when supercropping. By bending the higher branches downwards the lower buds receive more light. In this way you make the most of every plant. You stimulate the lower parts of the plant. Moreover, you also prevent plants from growing too big too quickly, thus facilitating a longer vegetative phase.

How do you switch from growth to flowering indoors?

Is everything clear so far? Great! It’s time to learn how to switch cannabis plants from the vegetative phase to the flowering phase in a grow room. During the growing period, most growers opt for a lighting schedule of 18 hours of light and 6 hours of darkness. Once your plants are ready for flowering, change this light schedule to 12/12. To do this, adjust your timer that you have connected to your lighting system. Once this is done, continue to care for your plants as usual. Trust that they will develop healthily during flowering as well.

How do you switch from growth to flowering outdoors?

As mentioned, outdoor growers generally don’t have to worry about inducing flowering. However, do you want a second growth cycle or an early harvest? Then you can manipulate daylight to force flowering. You can accomplish this by building a structure around and above your plants. You cover this frame with a removable and completely light-tight cover. Once your plants have fully developed, you provide yourself with 12 hours of darkness. In this way you successfully say goodbye to the vegetative phase. But be careful with this. If you do not follow this new light schedule very carefully, plants will revert to the vegetative phase if there is too much light.

What do you do when development is uneven?

Suppose one plant grows faster than the other. What to do If you notice that some plants are ready to leave the vegetative phase earlier, topping or pruning is an option. With this strategy, you force the plant to follow the rhythm of the others. This way, they can enter the flowering phase at the same time. Professional Pruning Shears (102) View Be careful when using these methods on your plants. Excessive stress leads to reduced harvest weight. Keep an eye on your plants and don’t let your impatience for a quick harvest get the better of you. Even though you can harvest sooner, the yield is less and of lower quality. In the long run this will cost you money and time.

Can you activate flowering shortly after topping?

While we are on the subject of stress and buds, some growers wonder whether you can switch to flowering after you have just topped your plants Unlike the other information in this article, opinions are divided on this subject. If you ask us, we prefer to take our cannabis plants and their ‘feelings’ into account. After all, the growing process in itself is quite stressful for your plants. You amplify this stress even more when you top or prune. Moreover, the change in the number of light hours and the start of the flowering period is one of the most stressful moments for weed plants. Therefore, most growers will tell you to wait 1-2 weeks after topping to soak up the bloom. Yet there is also a significant group that believes that a recovery period of 5-7 days is sufficient. Every plant should reach harvest in good health. A recovery time of less a week may result in a less impressive harvest weight. That said, your choice ultimately depends on your time constraints and the health of your cannabis plants.