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The Vegetative Growth Stage of Weed

The Vegetative Growth Stage:

The growth phase which is also known as the vegetative phase begins the moment the seedling becomes visible on the surface of your soil.  This stage lasts until the beginning of the flowering stage. During the vegetative period, weed plants develop from tiny seedlings into large mature plants. Fan leaves will develop, absorbing light for photosynthesis, thus generating the energy the plant will need to grow.

Also during this phase, the trunk of the plant thickens to support the weight and structure of the plant.  Depending on the strain you have decided to grow different varieties of weed plants will develop different growth characteristics during their maturation.  Some varieties, such as auto-flowering varieties, are quite small and reach a final height of about 30-100cm.

Sativas vs Indica: Growth Stage

Sativa varieties can grow up to 400cm. Depending on the genetics of the plant, the number, shape, and size of the leaves will vary. In the wild, for example, develop under harsh conditions between the mountains of the Hindu Kush region which is known for its very desert-like climate. As a result, those plants will develop broad, large leaves as a defence mechanism to store water to protect their flowers from the hot sun. Sativa varieties, in contrast, produce plants with thinner leaves to provide sufficient respiration in the tropical and humid climates from which they originate. Below we take a look at the basics of a robust and stable growth phase for weed plants.

Basics and Logistic of the Vegetative Growth stage

The growth phase is the foundation upon which our precious flowers can develop. As the weed plants mature, a healthy and robust base will give your plants the best chance to produce flowers/buds.  This resilience will allow your flowers the opportunity to maximize their potential and quality, therefore, maximizing your yield.  The branches can be bent and tied to cope with the conditions of a small installation space.

Outdoor Growing Considerations

First, let’s look at the basics of growing weed plants outdoors. For this, you should select a suitable strain for the respective climate zone in which you want to grow your plants. As a rule of thumb, sativa dominant strains grow better in a tropical, or more of a humid climate, while indica dominant plants feel comfortable in a dry and hot environment.  When growing weed outdoors, your plants will have a few more potential challenges to contend with.  

Pests, Climate, and Temperature:

Pests, climate, and temperature will all affect your plants when growing outdoors vs indoors.  When dealing with pests, you may want to choose a  resistant variety which is ideal. These include weed plants that produce many trichomes which are particularly good since they help to control the temperature of the plants and the terpenes act as a defence against insects and pests. If necessary, organic insecticides can also be used during the growth phase.  Just always keep in mind that whatever you are using to treat the pests make sure that it is organic.  

Fan Leaves and Branches: Growth Stage

During the growth stage, you may require extra support for the branches. , and the size of its initial flowers or buds. Some sativa dominant species fully develop into trees during their growth. Since you do not have any spatial limitations when growing outdoors, the branches can break off under their own weight if they get too big and are not supported. Therefore, it may be a good idea to tie the branches or support them in some way.  In addition, you can apply topping or trimming techniques, resulting in bushier and more stable plants.

In the Growing Area: How much space is enough space?

In most cultivation areas, limited space is available to the plants during the growth phase. When growing indoors, for example, growers often rely on indica or auto-flowering varieties, because they develop relatively small plants. Plants with sativa dominant properties are sometimes better grown outdoors since they require a bit more space to grow.  After they have started flowering, the plants of sativa varieties can grow threefold in height. Some growers use a method called SOG or ScrOG training to direct the growth of the plants and to ultimately increase their yield. These techniques are more for advanced growers and require specific knowledge between the different strains. Before inexperienced hemp farmers deal with these techniques, a few harvests should be used to gain experience.

The Duration of the Growth Stage and Lighting Concerns

How can growing outdoors affect the vegetative phase?  When growing outdoors, you will not have any control over the light cycles.  Therefore, you will need to time the vegetative stage accordingly so that once fall comes around your plants are going to be ready to flower.  If you want to grow weed plants for 5 months, then they should be planted 5 months before the beginning of autumn.  Once autumn comes around it will cause the photoperiodic varieties to flower.

For example, if autumn starts in August and you want to grow the plants for 5 months, seeds should be sown in March. The duration of the growth phase depends mostly on the variety and your preferences. If growers want to have large plants, they will keep them in the growth phase for a long as long as possible.  If grow space is limited the plants are to remain as small as possible, then you may want to sow in your seeds in April. 

Auto-flowering weed strains based on Ruderalis genetics have a very short growth phase due to their development in colder climates. For this reason, they should be planted during the two months with the most hours of sunshine (June/July), as the small and fast-growing plants can then thrive in the best conditions.

How Can Growing Indoors Affect the Vegetative Phase?

When growing indoors, your plants are not dependent on a change in the seasons to start the flowering stage.   Indoors you are able to control the light cycles completely so you can tailor that to the vegetative stage specific to that particular strain.  Therefore, it will not matter what time of year you sow your seeds. 

To preserve massive plants, they should be kept in growth for as long as possible. During growth, weed plants typically receive 18 hours of light and 6 hours of darkness.  Within the Grower community, there is a consensus that the best results can be achieved during the growth phase with a light cycle of 18/6. Eighteen hours of sunlight signals to the plant that it is spring and summer, and time to grow. By maintaining an 18/6 light cycle, growers can keep their plants in the growth phase indefinitely.

If you are interested in cloning your plants, an original or “Mother” plant (the weed plant from which clones are removed) must not pass into the flowering phase. Keeping them in a perpetual vegetative phase will allow the plant to continually provide clones.

Autoflowering Varieties: Vegetative Stage

If you have chosen an autoflowering variety of Cannabis plant you can expose them to an extended light phase of 20-24 hours per day in a growing area. The reason for this is that autoflowering plants are not totally dependent on the photoperiod. Since their genetic “growth clock” begins to tick after germination, their growth phase cannot be manipulated in the same way.

Irrigation concerns During the Vegetative Growth Stage

At the beginning of the vegetative cycle, the plants do not need to be watered as often, since small plants can absorb only very small amounts of water.  With this being said it is also important not to let your plants dry out too much.  Your soil should not feel dry to touch but cool or slightly moist is ideal.  Since the water supply can vary considerably depending on the cultivation medium, and climate, one can not say exactly how often the plants should be irrigated.  This is something you will get the hang of as you go. The plants should not get too much nor too little water, and it is advisable to work with a bit less water if you are unsure. Over-watered plants are as good as lost, while a shortage of water can be easily compensated. In this case, less is more. The water ideally should have a temperature of about 20 ° C, and if possible be filtered.

Helpful Hint:

When determining whether your plants are getting adequate hydration always remember to check your leaves for signs of too much or too little water.  Your soil and leaves will be the best bet to determine proper watering.

Nutrients Required During the Vegetative Growth Stage:

Nitrogen will be the most vital nutrient that your weed plants require during the growth phase. The NPK ratio (nitrogen-phosphorus-potassium) should be about 2: 1: 1 during this period. However, growers have different preferences and compositions. If the leaves have a healthy green colour and do not fall off, the nutrient content is just right.  Be sure to always check the health and colour of your leaves they will tell you to give you helpful clues along your way.

The Best Indoor Conditions that Support the Vegetative Growth Stage:


The best light for the growth phase in a growing area is provided by high-pressure LED and sodium vapour lamps. On a smaller scale, CFL lamps can also be used.  We discuss the differences in our Beginners guide to growing Cannabis check it out for more information regarding lighting.


When your plants’ roots reach deep into the cool soil, they will be able to cope with hotter temperatures of up to 38 ° C outdoors. The perfect temperature for plants in a growing area is between 21-29 ° C. At night, temperatures should be slightly lower and between 17-21 ° C.


During the growth phase weed plants cope with higher humidity. We recommend a humidity of about 60% if possible.

pH: For weed plants grown in soil, the pH should be between 6-6.5. When growing in a hydroponic plant, the optimum value is 5.5-5.8.


During growth, it is important to provide adequate air circulation to your ladies. Both outdoors and in a cultivation space like a grow tent or box, the plants must be exposed to a light breeze, so they can take up CO₂ and can give off O₂.


In the last phase of growth, the sex of weed plants can be determined. If you have purchased feminized seeds which is ideal if you are only looking to harvest then this is irrelevant as you already know the sex of your plants.  But if not, this is the point at which you will discover pollen sacs.  If your plants produce pollen sacs then you have a male plant and they will need to be removed from the female plants immediately.  These pollen sacs take the shape of mini bananas.  

When the female plants are pollinated by the male plants, the plants focus their energy on the production of seeds rather than the production of THC.  This will basically spoil your crop and produce a less than ideal harvest.

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