How long to vegetate a cannabis plant before flowering

All growers do things differently and as they complete more grows they will naturally form their own unique plans on how to effectively grow cannabis to a standard that suits them. But one of the most commonly asked questions from new growers is “how long should I vegetate my cannabis plant before sending it to flower”.

The truth is that there is no standard time to vegetate before flowering, it is simply whatever suits the grower and the grow space. That being said, the amount of time a plant is in vegetation makes a big difference to the end result. A plant that is properly matured will have a much bigger root system, leading to a larger plant and a far higher yield.

Below we will compare cannabis plants that have spent different amounts of time in vegetation, showing the difference in the root system, plant size, final yield, and quality of the bud. We will cover the results of 12/12 from seed (zero vegetation time) along with 1, 2, 3, and 4-week veg.

What difference does veg time make to a cannabis plant

The biggest difference in a longer vegetative period is the final yield. The difference in the quality of the bud is not as noticeable as some people think, however, switching a properly matured cannabis plant into flower will produce a slightly higher quality of bud. A four week veg is considered the minimum amount of time to produce a properly matured plant. Above we have a graph comparing different cannabis plant veg times to estimated final yields.

Results of 12 / 12 from Seed

12/12 from seed is a common practice that many growers prefer to do. This means that the plant never receives 18 hours of light that is required for the vegetative phase. As soon as the seed sprouts the plant is placed into 12 hours of light and 12 hours of dark which is used for making a cannabis plant flower. The benefit of using 12 / 12 from seed is that it saves a huge amount of time. The seedling will still grow into a small plant, but it will flower at the earliest opportunity, which is normally 2 weeks.

This makes for an incredibly fast crop but there are certainly drawbacks to this method. The yield will be massively reduced as the plant will have a very small root system. To combat this drawback some growers use a sea of green method which involves using small pots (normally 1 litre in size) and fitting as many seedlings into the grow space as possible.

Here is an image of the root system from a plant that received 12 / 12 from seed. The plant pot was 2 litres in size and the roots, whilst healthy, are not very well established.

Results of 1 week veg and flower

Giving a cannabis plant one week of veg before flowering is again common with Sea of Green growers using smaller pots. Often, instead of using one litre pots like above, the growers will use three litre pots as the roots have a little more time to grow and can use the space. The yield is increased when compared to 12/12 from seed and for the sake of just one extra week on the time scale many people would agree that this could be a better method than 12 / 12 from seed.

The image above shows the root system of a plant that received a one week veg before flowering. The root system is slightly better than 12 / 12 thanks to the extra veg time.

Results of 2 week veg and flower

When growing in bigger pots (about 8 litres +) the absolute minimum veg time would be two weeks – but 80% of growers would give the plants three to four weeks in veg. A two week veg from seed is quite rare as it is not really enough time to grow a full-sized plant with a strong root system.

If using a strongly rooted clone then a two week veg is more common as the cloned plant will be way ahead in terms of size and roots than a seed would have been. However, a three week veg for a clone is much more ideal if the cultivator wants a good yield.

The image above shows a seed that received a two week before flower. The pot size was 8 litres and as you can see, there is a lot of free space in the soil for a larger root system.

Results of 3 week veg and flower

If a cannabis plant has stayed healthy and strong since it sprouted then a three week veg can be adequite to produce a fair yield. Most growers do tend to opt for a four week veg minimum but plenty of people do flip to flowering phase after a three veg from seed.

If using rooted clones then a three week veg can be a perfect amount of time to produce a strong mature cannabis plant that yields very well.

Using a pot size of 10 litres is a common choice for plants that are going to veg for 3 weeks. This gives a nice amount of room for the roots along with providing a consistent environment for ph and food stability. Above we can see a marijuana plant root system that was developed with a three week veg before flower. This is a 10 litre pot and the roots have managed to spread all over the medium.

Results of 4 week veg and flower

Giving cannabis plants a four week vegetative period is commonly agreed as the best amount of time before flowering. As long as the plant stayed healthy throughout the four weeks then it will be nicely matured with a strong root system and capable of giving a great yield by the time the flowering period is finished. Some people do like to veg for a longer amount of time and there is no problem with that, but four weeks is a great option for most people.

It is recommended to use a larger sized pot between 10 to 15 litres in size when veging for four weeks as this gives the roots enough room to not become restricted which allows the plant to reach its full potential with the time given.

Above you can see the root system of a cannabis plant that received a four week vegetative period before flowering. The pot was 12 litres in size and there are plenty of roots showing around the perimeter. This plant could have potentially done with a slightly larger pot as it is close to being root bound, however, the plant remained healthy and delivered a higher than average yield of potent bud.

Conclusion – What is the best vegatation time before flowering

So as you can see above, there are multiple options when it comes to how long to vegetate a cannabis plant and the biggest difference between them is the final yield. Most growers prefer a four week veg but plenty of people opt for other lengths of time.

Over the course of a year, a four week veg can provide an average of four fully completed grows a year when using a fast flowering strain like these.

However, using a one week or 12 / 12 from seed technique a grower could bring down five grows per year which slightly helps to make up for the smaller yields they provide.

The best choice is really down to what suits the grower’s aims, so all these techniques are viable options.