cannabis groeifase

The Cannabis Vegetative Phase

Cannabis is a perennial plant that always moves through the same stages from seed to harvest. This blog zooms in on the vegetative or growth phase of cannabis. With this information, even novice growers will understand the basic principles of this developmental stage. We will explain the aim of the stage, what to look out for, and which grow techniques to apply or to avoid.

The Life Cycle Of Cannabis Plants

The growth stage or vegetative phase is a critical step in the life cycle of cannabis plants. In nature, marijuana crops complete a full cycle that starts with a seed and then proceeds through growth and flowering to fertilization. This produces the seeds that will repeat the cycle over the following year. This is how it has been for millions of years, all throughout the plant kingdom.

A female cannabis plant – the sex that ultimately produces the flowers growers are after – has only one goal: genetic survival, which requires passing her genes on to the next generation by reproduction. She ensures her offspring by developing female sex organs for male plants to pollinate. If that happens, she will develop the seeds that make up the next generation.

cannabis seeds veg stage

Zooming out from natural circumstances, if we look at grow rooms or garden grows, we usually don’t want seeds at all. That is why nearly all growers use female plants only, aiming at non-pollinated flower buds rich in THC and other valuable cannabis compounds. In fact, this means disrupting the plant’s life cycle, but as the cycle is completed, the plant will die no matter what – hopefully after passing on a bountiful harvest. No matter what, though, we won’t get anywhere near a flowering cola unless we successfully make it through the veg stage. Growth precedes flowering, so this blog is about the ‘groundwork’ a cannabis plant has to complete before she can present her bounty.

When Does The Vegetative Phase Begin?

Strictly speaking, the growth stage begins right after a cannabis seed germinates. As the seed’s shell bursts open, a root tip comes out ready to burrow into the soil, while a growth tip starts to climb upwards. First, however, the growth tip unfolds a pair of cotyledon leaves. These serve as boosters for the seedling, allowing it to develop true leaves and start growing.

After the initial cotyledons, the first true fan leaves emerge to reveal their characteristic serrated edges. Most cannabis growers and connoisseurs consider this to be the onset of the the growth phase. We could call the runup to this moment the germination or seedling stage, but even in this early phase, every effort is directed at growing towards full maturity.

cannabis vegetative phase
Seedling with cotyledons and the first true fan leaves emerging.

Quite obviously, the growth phase lasts until the moment when the first signs of flowering present themselves. That means the cannabis growth phase ends with a smooth transition to the flowering phase. In case of indoor grows, growers usually determine when the vegetative phase ends by ‘flipping’ their lighting schedules. As soon as a plant notices that the amount of (day-) light is lessening, it senses the days are getting shorter. This triggers the drive to start flowering, as in nature, this signals the beginning of summer’s end. Autoflower cannabis strains are the exception to this rule: they determine for themselves when to switch from the growth to the flowering phase.


Some (indoor) cannabis growers will try to prolong the growth phase for as long as they can. They may decide to do so because they want to keep a ‘mother plant’ alive for cloning purposes. Doing so demands preventing the plant from flowering, as the process of forming colas marks the irrevocable onset of her final life stage. This is only recommended for experienced growers: generally speaking, you’ll want to proceed from growing to flowering and then on to the harvest!

There is also a technique called revegging, which is only for veteran growers. Revegging involves ‘tricking’ a plant into reverting back to the growth phase after flowering is complete, which basically means ‘warding off’ or delaying the plant’s ultimate demise. Not only is this trick exceedingly difficult to pull off; the plant will usually  yield less than the original harvest. For most growers, that means it’s much easier and more efficient to simply start a new grow from seed!

cannabis vegetative phase

The Cannabis Vegetative Phase

In essence, then, growers and cannabis plants do not share the same grow goals or agendas. Still, that makes no difference in the vegetative phase: both parties simply want big, strong cannabis plants. In essence, the plant is setting the three basic conditions needed to ultimately grow colas:

  • The ‘framework’ that supports growth of buds: the stem and branches;
  • The leaves required to fuel growth and flowering through photosynthesis;
  • The roots a plant needs to absorb water and nutrients essential to its growth.

Cannabis plant growth depends on photosynthesis, the biochemical process that allows plants to use energy collected from sunlight. This results in storage of sugars that will power countless other reactions in turn. This is how the plant can fully mature in the flowering phase, complete with big fat buds full of resin, trichomes, terpenes, and more.

Growers can help cannabis plants reach their full growth potential. Below, you will find important tips to guide a cannabis grow safely through the vegetative phase on the way to a whopping harvest.

How To Help Cannabis Through The Vegetative Phase

Paying close attention to the following aspects gives marijuana plants the best shot at making it through the vegetative phase and on to a big time harvest result.

Proper Soil

Using the right type of soil is literally the groundwork for any successful cannabis vegetative phase. It accommodates development of a healthy root system needed to supply water and nutrients throughout the vegetative phase. Although there are about as many soil best practices as there are growers, this blog explains what any grow medium should contain as a bare minimum.

Make sure you use spacious pots. After germination, be sure to transplant your seedlings to keep providing enough room for continued root development throughout the vegetative phase. This blog explains root growth and health in detail.

water cannabis vegetative phase

Water And Nutrients

No cannabis plant can manage all of its growth on (sun) light alone. Successful completion of the veg phase also requires water and a whole range of minerals. These are mainly supplied by the roots, provided these are able to do their job. For that, they need soil with sufficient humidity, the right nutrients, and the right acidity. Make sure to give cannabis plants enough water (but not too much) throughout the vegetative phase: the same applies to nutrition (definitely don’t overdo it on the nutes). The most important building blocks for growth is nitrogen (N), but in fact, cannabis plants need just about all the nutrition ingredients they’ll require throughout their life in this phase. This blog tells you more about the basic nutrient compounds needed for good growth.

The Sweet Spot

Outdoor grows thrive in the garden’s sweet spot, where all the cannabis grow conditions are in optimal balance. This will ensure a plant gets all the space, sunlight, and fresh air it needs for healthy growing.

Indoor grows call for optimal control of environmental conditions all throughout the vegetative phase. This includes proper lighting (sixteen hours of light and eight hours of night-time dark in the growth phase), good ventilation, adequate air humidity, and minimal external disruption. Make sure that your plant has enough space to grow. Some strains will start to race towards the lights in the veg phase, which can be a real problem in small grow tents. Moreover, if plants grow to close to the lights, heat stress and resulting damage can stunt their healthy development.

veg stage


Watch out for the phenomenon of ‘stretching’, too. This is a deviant growth pattern marked by growing almost exclusively through developing long, thin stems. This blog explains what causes stress and how to prevent it.

Training Cannabis In The Vegetative Phase

The vegetative phase is also the best time to implement many of the techniques used to improve cannabis bud production once flowering sets in. Many of these techniques aim at persuading plants to develop more side branches, lateral growth, or optimal spread to make better use of available light.

Our Grow Blogs contain all the knowledge required to implement well-known techniques, including:

amsterdam genetics

Getting To That Harvest

Once the vegetative phase is completed successfully, the moment arrives to either flip the lights or discover the first signs that your outdoor cannabis is flowering. This is the point where the veg phase ends. From here on, your plants will have different needs, but those are the subject of another blog. If you manage to make it through a successful flowering phase too, the time has come to harvest those buds, trim them, and then dry and cure the flowers you’ve worked so hard for!

But let’s stick with the subject for now – we’re not there yet. First, any cannabis grow deserves all the love and attention it can get to make it through the vegetative phase in prime shape. That means it’s time to pick you best match in cannabis seeds and start your own budding grow adventure!

Order Your Seeds