The Effects Of Underwatering Your Marijuana Plants

All plants, including marijuana, consist of about 80% water. Therefore it makes sense that issues with the water management could cause damage to the marijuana plant. Ourdoors in the ground, the marijuana plant usually has enough soil to work with. Depending on the quality and the structure of the soil, it also helps to regulate the amount of moisture. With indoor cannabis cultivation in pots it’s highly likely that the plant gets too much or too little water. The risks indoors are a lot greater, that why watering of the marijuana plants needs to happen with the greatest knowledge and care.

The water requirement of a marijuana plant is high, but a large portion of the water is also excreted from the plant again. This occurs through evaporation from the leaves. A small amount of all the water remains behind and is used as building blocks. On the way to the ‘construction site’, the water has also helped to absorb and transport the nutrient salts and carbohydrates.

The marijuana plant possesses over a perfect biological mechanism, so it is able to manage the available water as efficiently as possible. Sometimes the plant does not succeed to adjust the available supply and demand of water properly. In almost all cases, this is due to external causes. For instance when you forget to water it, or in all enthusiasm give too much water. A lack, or an excess of water always means that the plant could be doing better. This article is part of my e-Book “ The Marijuana Grow Bible”.

Make sure to download my free marijuana grow bible to learn more about underwatering.

In severe or prolonged cases the marijuana plant may even die. A shortage of water has a number of consequences. Since water is essential for photosynthesis, the lack thereof will reduce the photosynthesis in the plant. Furthermore the plant will, to carefully manage the available water, close the stomata on its leaves. As a result, less water evaporates and therefore the plant also absorbs less water. Consequently, it also means that no CO2 can go through the plant.

Dropping Marijuana Leaves

A lack of water supply causes a stagnation of the nutrient supply from the ground as well. Not enough nutrients means a shortage in protein production. The marijuana plant will show signs of nutritional deficiency in no time. Adding fertilizer is useless, because the plant can’t absorb it anyway due to the lack of water. So the symptoms of such a nutritional deficiency are therefore secondary: they refer to another deficiency. It’s always of great importance to identify the primary issue (shortage) of a sick marijuana plant because otherwise the problems can only become greater rather than smaller.

A third consequence of a water shortage is that the marijuana plant is going to breathe faster. This is because the plant has to put in a lot more effort to loosen the remaining water in the ground. This takes a lot of energy from the plant, energy that can no longer be diverted to growth and flowering.

A lack of water can be identified by:

  • drooping leaves
  • leaves becoming brighter
  • leaves that shrivel suddenly
  • leaves that wither eventually
Discoloring marijuana leaves

Determining the right diagnose is not as simple, because these symptoms look a lot like the signals the marijuana plant gives if there’s an abundance of water. This is for the simple reason that in both cases the same biological processes stagnate. When you encounter these symptoms always check to see if too much, or not enough water has been given.

Too much water causes the roots to be too wet, so they take in less oxygen. The roots themselves are affected by the moisture, soften and eventually die. The marijuana plant is very vulnerable due to its fine root system.

It takes a long time before a marijuana plant recovers from damaged roots, and a lot of things can go wrong in that time period. Not only the growth is less successful, it can also come to a complete halt. Moreover, the plant loses its vitality and becomes very vulnerable to pests and diseases.

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Robert Bergman

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Robert Bergman


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

12 comments on “The Effects Of Underwatering Your Marijuana Plants”

  1. Bunny, I have the same question. I have an outdoor in ground grow and I have dug Fox farm soil in each plant (3) hole for the past 4 years so the area had ver good soil.. My buds are about week 4. I have a drip system and water everyday so they are getting about a gallon per day. I use fox farm fertilizer and I think it might be time to use ‘Cha-ching” (Humbolt) for my bud development, about once per week starting this week. Some one told me that I should not water every day at this stage. Is this correct? Also, I hear about the need to ‘flush’ the soil at this stage. How does that differ from just watering?

    • Hi all im a new grower im usin a 300w roleado full spectrum dimmer grow light 2 chocolate chunk in new horizon compost in 3 gal smart pots and its wk 3 of flowering an the roots are growing throught bottom of the pots wot am i to do repot in bigger pots or just leave them be ?

    • Bunny,

      Watering st the end of season in relation to what? You always watrer your plants to the end. IN the final 2 weeks a lot of growers believe in doing a flush with plain PH’d water. to allow the plant to use nutrients stored in the plant.

      I suggest you join our support forum.

      Happy growing! 🙂

  2. Oh and Jason your plants are in their vegetative state at this stage and should be on their 4th or 5th node atleast by the three week mark and receiving atleast 18 hours of light per day to facilitate rapid growth approaching the flowering stage. Now is when you should think about topping your plants and start to train them to grow the way your indoor setup requires…hope this helps you too and also Happy Growing Ganja Bro!!!

  3. Well Daniel the roots thrive in a hydroponics situation due to the fact that the nutrient solution in a hydroponic setup is highly oxygenated using a high output air stone(or several) in the nutrient reservoir. Also the fact that the solution is constantly moving helps to oxygenate it as well…hope this answers your question, cheers and happy growing!!

  4. Yes I have a few questions. I am first time grower. My plants have been growing for about three weeks,what stage should they be in,or how many sets of leaves should I be seeing,this is a inside grow

  5. I have a question that you could perhaps answer. It is acknowledged that too much water for a plant potted in soil is not good, why do plants thrive in hydroponic situations where their roots are constantly immersed in an aqueous solution?

  6. you should be given them a gallon on mostly everyday if they ‘re in flower because they need more than .that’s most growers are watering from the bottom by putting the buckets then have been some kind of a deep dish and then heading up to gallon of water a day in that dish give upto a gallon a day and see how they are drinking it . sometimes what we do is we dump the water on the top see how much runs out into the tray and then fill the tray almost to the top which is usually about 3 inches then we watch to see how long it takes for them to drink the water. We trying to continuously feed from the bottom in the train get all those root down

  7. When my plants start flowering about week 2 of flowering then i water my plants 1 gallon of water every other day. They seem to love it becouse they growing about 1 to 11/2 inches a day. The days are pretty hot and the dirt in the buckets are about dry when i water every other day. And I’m growing white widow outside in 5 gallon buckets and 7 gallon buckets. P.S. I’m from Tennessee