When to Flip From Veg to Flower

Some say that the key to life is divine timing – but I won’t claim to know the answer for life. As for growing cannabis, it’s one of the most important factors.

It’s essential to know when: when to be light, when to be dark, when to water, harvest and of course, when to flip from veg to flower. It is extremely common for new growers to wonder when it is time to induce the flowering stage for their cannabis plants, and most of the information available is vague.

There is no strict rule on when to switch your plants from the vegetation stage to the flowering stage and it will depend on a lot of different factors, such as the amount of time and space you have to work with. The amount of time the plant spends in vegetation will also depend on the strain and whether you are growing from seed or clone.

In this case, copying another grower’s timing schedule won’t be of any use, unless they are growing the same strain in the same setup and with the same amount of space. To know when to flip from veg to flower, the grower should consider all the factors that are specific to their growing setup.

This article is a comprehensive guide to the basics of timing. With all the information covered here, you should know enough to be able to make an informed decision about the perfect switch time for your cannabis plants.

What does it mean to flip?

To start with, before you go flipping, you should remove all the male plants from your garden (but don’t throw them away!). If they are left with the female plants during flowering, you will end up with seeds instead of buds. So, what does it mean exactly to flip from veg to flower?

An indoor grower’s task is to successfully mimic the elements indoors. So, flipping is a way to tell the plants that the seasons are changing by increasing the number of hours they spend in the dark. More specifically, this means changing the light/dark cycle from 18/6 to 12/12.

Female plants will not begin to develop buds until they enter the flowering stage. This means that the moment you switch the light/dark cycle, plants will stop sending energy into root development and start sending it into flower development.

Related post

Cultivation

Hermaphrodite and Mixed-Gender Cannabis Plants – And How to Avoid Them

Emma Ryte
21 Jun 2016

Consider the maximum plant height

The most important factor that is going to decide when you flip from veg to flower is the amount of space you are working with. If you veg for too long in a small grow space, you risk your plants growing right into your light fixtures and getting burnt.

To avoid this, you should consider the maximum height your plants can safely get without being disturbed by the ceiling or light fixtures. You shouldn’t really let your plants get closer than about 30 cm from your light globe. You can afford to be a few centimeters closer if you are using cooler lights, such as fluorescent or LED lights. You could be risking frying your plants if they get any closer.

This means you also need to consider the light fixture for the environment you are growing in. Some light globes get hotter than others, so consider the size of your space and the lighting that you are choosing. The longer your plants are in the vegetative state, the taller they will be.

How tall you let your plants get in the vegetative state will depend on what kind of cannabis you are growing, which we will cover in the following paragraphs. So, it’s far too vague to say that 3 or 4 weeks vegging out is the right time. It will all depend on your grow space and the kind of weed you have growing.

Are you growing indica or sativa?

Now that you know the maximum height your grow room can facilitate, it’s time to consider your strain. The strain of cannabis you are using is going to be the most important deciding factor of how tall to let your plants get before switching to the flowering light cycle.

Indica strains are famous for being shorter, bushier plants than sativas, and during the flowering stage both kinds of cannabis behave differently.

As a general rule, your indica plant will only gain 25%-50% more height during its flowering stage. This means that if you let your plant get to 60 cm tall during vegetation, it will probably only be a maximum of 90 cm tall at harvest.

On the other hand, sativa plants are known to grow much taller than indica strains. They are known to continue shooting upwards even throughout the flowering stage, meaning that a plant that is 60 cm tall at vegetation could grow to be as tall as 180 cm.

Keep in mind that this general rule applies to pure sativa strains, which are rarer strains of cannabis. Most indoor growers will be growing indica or hybrid strains, unless you are operating in a commercial setup which allows for the size of tall sativa plants.

Many cannabis growers opt for hybrid strains because they have the kick of a sativa without taking up all the room. The basic rule for a hybrid strain is that it will double in size between flipping and harvest. If your plant is 60 cm when you flip from veg to flower, you can expect it to grow a total of about 120 cm.

Let the height of your plant be the major role player in choosing when to flip. If you want to leave about a foot between your light and the growing medium, your plant should never get taller than that distance.

Measure your maximum height, and use the mathematics above. As an example, if the distance between your highest possible light fixture and your growing medium is 150 cm, then your plant shouldn’t get any taller than 120 cm.

When to flip: Clones vs seeds

It doesn’t matter whether you are growing from clones or seeds, the above rules still apply. However, it is important to consider that your planting method is going to affect how long plants stay in vegetation.

If your plant hasn’t developed a proper root system, then your flowering is going to be disappointing. For this reason, it is important to let seedlings or clones develop a proper root system before officially confirming that it is in the vegetation stage.

As a general rule, some growers say the first set of true leaves marks the beginning of the vegetation period (in the case of growing from seeds). When it comes to clones, they can grow much faster than seedlings and vegetate quickly. It is important to watch your plants carefully in the beginning stages of their lives.

So, keep in mind that in the case of clones, although they may look ready to flip, they may not have developed a root system sufficient for flowering yet. They can grow tall very quickly, forcing a grower to flip, but in reality, the roots are not big enough yet.

Growing style and training methods

The style you are using to grow will also determine how long you choose to veg before you flip to flower. Some growers have adopted specific growing styles to maximise the yield but minimize plant height, in which case the vegetation stage is much longer than normal.

Super cropping is the technique by which growers bend the taller branches of their plants down, making them grow outwards instead of upwards. This will mean a longer vegetation time, as the purpose of this growing style is to produce an enormous yield.

Sea of Green (SOG) or Screen of Green (SCROG) are other cannabis growing styles that involve growing through a netting system. These systems encourage shorter plants that only develop one flower.

The purpose of these growing methods is to make good use of horizontal space when there isn’t much vertical space. In this case, the vegetating time is much shorter, as the plants are not really allowed to get very tall.

These are examples to show you that what you are looking to achieve out of your grow room is ultimately going to decide when to switch from veg to flower.

If you are working with a very narrow and small space, you might be adopting methods such as the SCROG style. If you’ve got heaps of floor space but no vertical space, then maybe you will adopt a super cropping method.

In both situations, the veg time is different. It is all up to the grower and what they want to achieve.

Plant heights will vary

If you’ve grown weed before, you know that there is variation between plants even if they are of the same strain. The best way to manage this is by pruning and topping. It gives the shorter plants time to catch up to the taller ones and it also encourages a bigger yield.

You should always treat your plants as individuals – and separate pieces of art – because they respond differently to one another. There is no rule book about how to treat cannabis plants. It is a dynamic process that requires you to be sensitive to the needs of your plant and your desires as a grower.