Different types of stress in marijuana plant

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Imagen de una planta sufriendo estrés
Image of a plant under stress



Did you know that cannabis plants can also be stressed? That’s right, this increasingly common disease in humans also affects our favorite plants, and just like it happens to us, stress appears when plants are exposed to abnormal situations, whether environmental, nutritional, or due to agents. external. Plant stress does not always have to be negative, in some cases it can cause an increase in the yield of buds, resin or essential oils, but in general it is bad. The symptoms of stress in marijuana manifest themselves in different ways, depending on the type of stress or the general health of the plants

When female cannabis plants are stressed, they can produce fertile male flowers that can pollinate other female flowers of themselves or other plants, but they do this as a defensive mechanism, since stress makes plants understand that something it does not go well and it could die, and in response they try to self-pollinate as a last resort to ensure offspring, which after all is the main mission of plants in nature. In this post we are going to see several types of stress in marijuana plants, so you can see the reasons, the symptoms, and how to solve this problem, so relax, don’t get stressed, and I hope you enjoy reading.



📲 Water stress in marijuana plants



Water stress can be caused by an excess or deficit in watering the plants, but the former is more common. It is very important to respect the dry cycle between irrigation and irrigation, since during this time the root system is oxygenated and if this is not done it can cause a stress situation that can have disastrous consequences. The consequences of water stress caused by a deficit or lack of irrigation are a decrease in the development of plants, flaccid or fallen leaves, and discoloration and wilting of the leaves that, if not corrected, can fall.

However, water stress due to lack of irrigation is easier to solve than that caused by excess irrigation, since the plants begin to recover when they are watered again. It is possible that the substrate can no longer absorb and withstand the moisture from the irrigation once it has dried out too much, in which case it is best to add a wetting product to the irrigation water such as Free Flow from Bio Nova, or alternatively add a couple of drops of fairy or any other dishwashing soap. Water stress can also occur due to poor drainage of the pots, for this reason it is recommended to put a base of balls of expanded clay or coconut fiber at the bottom of the pots to help evacuate excess water more effectively.

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Plants with water stress caused by excessive irrigation show decayed leaves that in some cases can curl, and some growers associate this with a lack of irrigation, which can aggravate the problem. The consequences of water stress caused by excessive irrigation can be lethal, because it can cause biotic stress that in some cases ends in the death of plants.


*image of a cannabis plant with water stress*
*Image of a cannabis plant with water stress*



🚀 Biotic and abiotic stress in plants


Biotic stress is caused by living beings that can be fungi or insects. In the case of stress caused by excess irrigation, the roots do not receive enough oxygen and hypoxia stress increases, and the biggest problem is that in many cases it ends in the appearance of fungi such as Pythium or Fusarium, and this usually ends in the premature death of plants. Nematodes or aphids can also cause biotic stress, but in this case the solution is much simpler, and if it is taken care of in time it does not usually cause many problems.

Abiotic stress is caused by factors that can be environmental such as temperature, light, air, CO2, or caused by us such as an excess of salts in the substrate, plant injuries, etc. As a general rule, it is easier to solve than biotic stress, since it is enough to set the ideal parameters for the plants to grow or flourish normally.



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✅ Light stress in cannabis plants


Light stress on weed is one of the most common in both indoor and outdoor cultivation. Photoperiodic marijuana plants are based on the hours of light and darkness per day to determine their vital phase, it is how their biological clock marks their cycle. Obviously, plants do not have a clock or calendar, but they perfectly control the time of darkness because during the night cycle they accumulate a protein that, depending on the amount produced, activates the change of cycle, from growth to flowering. If the light or dark phase is interrupted, the plants understand that something is not going well, they get stressed and in response to the stress they slow down their development and from there, if it is not solved soon, there may be negative consequences.

The cycles of the plants must be respected, if we set a photoperiod of 18 hours of light per day for 1 month of vegetative growth, it cannot be that some days have 18 hours of light and other days have 15 or 20. During the night phase it is still more important, with respect to total darkness, it is not worth turning on the light for a moment to see the state of the plants, not even 30 seconds. In the case of having to see the crop during the dark phase, the ideal is to use green light, since this color does not bother the plants.

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The signs or symptoms of light stress in marijuana can be seen in a decrease in the rate of plant development, especially if it is in the flowering phase, since it stops the production of buds. If the problem is not solved quickly, the most sensitive plants to stress can show signs of hermaphroditism and even ruin the harvest. In the case of seeing male flowers on a female plant, it is best to remove it from the crop and away from other plants to reduce the risk of accidental pollination.


*Photograph of a female plant that has produced male flowers due to light stress*
*Photograph of a female plant that has produced male flowers due to light stress*



🔥 Heat stress in marijuana plants


Heat stress is one of the most common in indoor cultivation, since it occurs when the temperature is too high for the plants, normally above 30º C. The symptoms of heat stress in marijuana are quite evident because they tend to curl towards up the edges of the leaves, something that plants do as a mechanism to help them transpire more and thus be able to better withstand high temperatures. Heat stress in marijuana plants grown outdoors manifests itself in the same way as in indoor cultivation, in this case it usually occurs only in summer and when the plants are in small pots.


*image of a cannabis plant with heat stress, where you can see the edges of the leaves turned up*
*Image of a cannabis plant with heat stress, where you can see the edges of the leaves turned up*

How to recover marijuana from heat stress?

In indoor cultivation, the ideal is to separate the focus of the plants so that the heat it emits does not affect them. LED lights barely heat up and can be a good solution in this case, otherwise you have to place a thermometer or its probe at the height of the highest tips of the plants and raise the focus as necessary so that the temperature that plants feel does not exceed 25º C. Another interesting option would be to increase the ventilation of the crop, putting a more powerful extractor that can evacuate a greater amount of hot air, or putting more fans to improve interior aeration.

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In outdoor cultivation it may be necessary to change the location of the plants during the summer so that they do not receive as much direct sun, and in cases where they cannot be moved because they are planted directly in the ground, the ideal is to place a shade in the upper part that protects the plants from excessive heat.



🎯 Cold stress in cannabis plants


Cold stress in marijuana usually occurs more in outdoor cultivation than indoors, and when temperatures drop below 15º C but it depends on the variety grown because there are some that are more resistant than others, such as high mountain landraces. The symptoms of low temperature stress in cannabis plants can be seen as a slowdown in the rate of development, which at a given moment could even come to a complete stop, and if not resolved, the plant will stop eating and little by little it will wither.

The solution is simple, increase the temperature to place it between 22º C and 27º C, something that in indoor cultivation is as simple as bringing the focus closer and “playing” with the air extraction. On the other hand, when plants are grown outdoors, it is not so easy to raise the temperature, and in this case we only have the option of protecting them in a greenhouse or similar, and if possible, place the plants in the sunniest place in the garden.



👾 Nutritional stress in marijuana plants


This type of stress is also very common, because each plant may have different nutritional needs, and sometimes it is not easy to choose a good dose of fertilizer. Nutritional stress can be caused by fertilizing with too much food, but it can also be saline stress caused by an excess of salts in the substrate that prevent proper absorption of the elements, and for this reason it is also known as osmotic stress.

The symptoms of a plant stressed by watering with an E.C. too high are reflected as overfertilization, and it is very evident because the leaves acquire a very dark green tone, the claw-shaped tips curl downwards, and in some cases chlorosis or wear may also appear on the tips. On the other hand, saline stress can be seen as certain deficiencies of elements or microelements, with various types of discoloration on the leaves, spots, dots, necrosis, etc.

The solution in all cases can be a root wash with a lot of clean water and with the PH adjusted so as not to cause another problem while we solve this one. In the case of a slight punctual overfertilization, it would be enough to irrigate with abundant water until we see clean water draining. E.C. can be measured. of the drained water to check the amount of food contained in the substrate. But if it is osmotic or saline stress caused by a large accumulation of salts in the substrate, it is best to water each plant with an amount of water 3 times greater than the volume of the pot, that is, if it is 7 liters, it will be necessary to use about 21 liters of clean water.


*photograph of a marijuana plant stressed by overfertilization, clearly showing the claw shape of the leaves, their darker color and slightly burned tips*
*Photograph of a marijuana plant stressed by overfertilization, clearly showing the claw shape of the leaves, their darker color and slightly burned tips*



🧐 Conclusion


Marijuana plants can become stressed when they are affected by incorrect environmental parameters, pests, poor nutrition, and several other factors that we have reviewed in this article. The response of female plants to stress in many cases is to produce male flowers to self-pollinate, create marijuana seeds and thus guarantee the continuity of the progeny. If your intention is to harvest seedless buds, the best thing is for the plants to have everything they need so they don’t get stressed, and for that, the ideal is to be very clear about everything we have seen today, especially if you grow varieties prone to hermaphroditism as are most American genetics today.



⚠️ Frequent questions


How to know if a plant is stressed?

The first symptom is the slowdown in the growth or flowering rate, if you see that the plant stops developing at the same speed, it is recommended to review all the parameters to check that everything is fine, because if it is not treated in time, others will begin to appear later more serious problems.


Will marijuana plants recover from heat stress?

Cannabis plants have a power of resistance and adaptation that allows them to recover from practically any situation as long as the problems that have created stress are solved, of course. In the case of heat stress they recover quickly, but in some plants there may be a decrease in yield if they have lost leaves or it has taken a long time to solve the problem.

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Fran Quesada Moya
Fran Quesada Moya

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