How cannabis plants grow is extremely relevant as their structure is going to withstand the weight of the flowers. Therefore, a mistake during this stage could damage the crop. The stretching of cannabis plants can be a real problem for a correct development. If it’s not sorted out soon, it could promote unstable and weak plants, which could mean a ruined yield.

Cannabis plant stretch is the prolonged vertical development of marijuana plants during the growth and flowering phases. Indoor growers try to avoid this from happening as it weakens plants and creates other problems such as: decreased yield, less indoor space, long internode distance and other serious conditions.

What causes the stretching of cannabis plants?

Being aware of all the aspects of the crop is a great advancement when it comes to finding a solution. Vertical growth could derive in plants not receiving enough light, absorbing less nutrients or producing less yield. Knowing exactly what causes plant stretch and how to fix it is essential to at least mitigate its effects.

stretching of cannabis plants


Plants’ genetics can determine if they’ll stretch more or less. Indica strains are short and bushy, which complicates vertical growth. However, sativas do stand out in growth and can easily surpass 2 m in height, in plenty of cases.

It’s very important to acknowledge the characteristics of the grow, as each seed requires a certain space and care. Detecting if a strain has a tendency to stretch, although it’s not negative in itself, could prevent the loss of up to 25% of the yield.

Lighting Exposure

Another crucial point to detect possible plant stretches is lighting. The lack of a good quality light source or too much distance between the plants and the lamp forces them to stretch in order to receive enough light to develop. If there are too many plants in the provided space, it could provoke a generalized stretching and a fairly decreased yield. The key to avoid this is to place the grow lamps at an intermediate distance, not too near nor too far.

However, distance is not the only cause for plant stretch, certain types of lighting could also promote it. Bulbs with reddish or orange tones, such as HPS bulbs, which mimic autumn sunlight, could also favor stretching. Yellow, white and blue (cold colors) tones, present in LEC and LED bulbs, prevent plants from stretching

cannabis flowers

Temperature of the Grow

Here you could find two causes that would involve temperature in the stretching of plants. First of all, if the temperature inside the grow tent is higher than 27 °C, branches will grow uncontrollably. This is why it’s so important to keep grow lights between 30-50 cm from plants. An unstable environment will promote excessive growth and the weakening of plants.

On the other hand, light and dark hours play a huge role in the final development of the grow. Too much of a difference between day and night temperature could promote the production of gibberellin, a substance that increases the stretching of stems. To avoid this, it is best if the difference in temperature ranges between ± 5 ºC. Some studies suggest that the stretching of cannabis plants takes place in the first hours of the morning, therefore, a higher night temperature could reduce stretching and be beneficial for the plant.

Proper ventilation

Although it might seem ridiculous and senseless, proper ventilation is very useful to improve plant vitality. A good airflow reduces high temperatures and creates a more comfortable atmosphere for plants. Using fans inside the grow area strengthens branches and forces plants to create a more compact structure in order to withstand the wind.

Shape and prune the plant

Applying techniques to adjust plant height and distribution is very useful to avoid undesired plant stretch. One of the options is to perform an apical prune on the tip of the stem for the plant to center in producing in a concrete area, but doing so could decrease the yield. However, if there is enough horizontal space, the branches can be bent to force them to expand towards the sides. This prevents stretching and maximizes the yield. Using stakes and other pruning methods such as SCROG or SOG could also help reduce vertical growth.

cannabis plant

Prevent the stretching of cannabis plants to improve the yield

Regardless of everything that has been mentioned, it is normal for plants to stretch during the early growth and flowering stages because they always try to absorb as much light as possible and growth is more or less established by the genes. What a grower has to find is the proper equilibrium between proper vertical growth and radical plant stretch. In order to get full control of the process, it’s very important to follow the advice provided in this post. Factors such as proper air flow, space between plants, correct temperature, stakes and pruning techniques could all be helpful in avoiding this excessive growth problem. Improving the quality of the grows by looking for solutions that reduce plant stress is the best solution to prevent plant stretching and obtain great results. 

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