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How To Fix Overwatered and Underwatered Cannabis Plants

How to diagnose, the way to restore including our top tips to help you on the way to becoming the ultimate grower.
12 May 2022
12 min read
How To Fix Overwatered and Underwatered Cannabis Plants

  • 1. Overwatering cannabis plants
  • 1. a. What are the signs of overwatering?
  • 1. b. How to fix overwatered cannabis plants
  • 1. c. How to avoid overwatering
  • 1. d. Top tips
  • 2. Underwatering cannabis plants
  • 2. a. What are the signs of underwatering?
  • 2. b. How to fix underwatered cannabis plants
  • 2. c. How to avoid underwatering
  • 2. d. Top tips
  • 3. The importance of water purity
  • 4. Monitoring ph levels
  • 4. a. What is ph?
  • 5. Monitoring ppm levels
  • 6. Using reverse osmosis water
  • 7. In conclusion

There is a balancing act to how much water a Cannabis plant uses, and depending if it is absorbed by the roots, or through the foliage via transpiration. For a beginner grower, attempting to find the balance can result in either overwatered cannabis plants or in underwatered cannabis plants. In this article, we explain how to diagnose the problem, the ways to restore it, and our top tips.

1. Overwatering Cannabis Plants

Overwatering is common amongst new growers, this occurs when watering in excess or a combination of too much water and poor drainage or poor growing conditions. There are many valid reasons why a Cannabis plant that is being grown indoors or outdoors, can become overwatered. The main one is down to inexperience combined with the illusion that the more water and nutrient solution is given, the faster the plants will grow.

Reasons for overwatering

  • A poor-draining growing medium.
  • An overzealous beginner grower.
  • The pot size is too small.
  • The growing medium is cold.
  • Over-frequent feedings.
  • Feeding when lights are off.

What Are The Signs Of Overwatering?

A Cannabis plant may not show symptoms or any signs of being unhappy immediately after being oversaturated. But after some time, overwatering cannabis will cause the leaves to droop in a downwards fashion as if they have chosen not to photosynthesis as once before.


How to fix over and underwatering: signs of overwatering

Symptoms of overwatering your cannabis plant.

Signs of overwatering in cannabis can be really bad due to the excess amount of water in the growing medium, the plants will struggle to offload the water through transpiration. This will completely disrupt the growth, nutrient uptake, and cause a grower to abandon their vapor pressure deficit chart. Depending on how thick and dense the growing medium is, can also determine how little the amount of dissolved oxygen present will be.

How To Fix Overwatered Cannabis Plants

Overwatered cannabis plants may show very grave symptoms but it is relatively easy to fix it. The easiest thing to do is simply to allow the growing medium to completely dry out, before considering watering again. By giving your plants 2-3 days to dry out and fill the roots with oxygen and fresh air, the roots will be encouraged to search out for new air pockets. The dry conditions will also prevent bad bacteria from thriving and limit the development of pathogens that depend on high moisture and low-oxygen environments.


How to fix over and underwatering: how to fix overwatering

Fill the roots with oxygen and fresh air to restore your plant from overwatering.

How To Avoid Overwatering

There isn’t much that you can do to avoid overwatering your cannabis plants, but by following a couple of things you can avoid any symptom that causes a major problem and have a much smoother grow cycle and grow healthier plants. First of all, allow the growing medium to dry a little bit between waterings, as a guideline, you should only water when the growing medium is around 60-70% dry, this can be hard to know if you don’t have a soil moisture sensor so we recommend lifting the pot before and after watering so you get an idea of the weight of the pot and know when to water; You can also stick your finger in the growing medium and if it’s moist you can go ahead and water. Secondly, make sure your growing medium isn’t too compact so there’s enough drainage for the excess water to drain.


How to fix over and underwatering: how to avoid overwatering

You should take into consideration the stage your plants are in when watering.

And last, make sure you are watering according to your plant’s size and not the size of the pot; Most beginners growing in bigger pots usually water a lot due to thinking the plant needs more water but despite being in a big pot, if your plant is in the seedling stage it will need less water than when flowering, even if it’s in a 20L pot, so make sure you water accordingly.

Make sure to check the pots

If you’re growing in regular plastic containers make sure there are enough drainage holes on the bottom to allow for good water drainage, if there aren’t enough, you can drill them by yourself. Now, if you’re using fabric pots or air pots, make sure you don’t leave the runoff sitting in the saucer so the substrate doesn’t absorb the water back in.

Use the correct medium

Water retention is preferred in some cases but depending on your growing conditions it may cause overwatering so check your growing conditions and then mix your growing medium of choice with perlite, clay pellets, or any other soil improver.

Water less frequently

As your plant grows it will need more and more water but it can be quite hard to know the exact amount of water if you’re a beginner grower so it’s recommended you don’t water very often but if you’re forced to water often due to the growing conditions, make sure you use less water.

What To Remember

  • Allow your pots to completely dry out until they are very lightweight.
  • Check on the growth structure and vigor of the plants as they begin to respond.
  • Pathogens prefer low oxygen and wet conditions to live.

Top Tips

1. It is better to feed smaller amounts of water or nutrient solution, on a more frequent basis. Younger plants prefer this method as it encourages maximum root growth potential and allows Cannabis plants to break down the food easier.

2. Avoid feeding late at night close to lights out, and especially when plants are asleep during the darkness period. It is best to water them after the first hour when lights have turned on.


How to fix over and underwatering: top tips

If you're having issues related to humidity it's better to water when the lights are turned on.

3. Using a pump and dripper lines connected to a plug timer will be your best bet at timing the watering times every day, without compromising the routine. An excellent way of reducing the physical work involved when watering.

4. The best way to judge how happy your plants are is to access them by appearance. Ideally, the fan leaves should be angled at 45 degrees facing towards the sky. When the leaves begin to droop and yellow, these are symptoms over or underwatering.

5. Be vigilant of foul-smelling odors developing inside the grow room. When using organic growing mediums and liquid feeds, it is very easy for the lowest parts of the pots to become a breeding ground for unwanted bacteria.

2. Underwatering Cannabis Plants

There can be several reasons where a cannabis plant is neglected and underwater. Sometimes it may not be practical to water your plants every day at the same time. However, once a growing medium has become totally dry, depending on how dry the air is it can lead to the plants becoming stressed, tired, and nutrient deficient.

Reasons for underwatering

  • Substrate not retaining water properly.
  • An apprehensive beginner grower.
  • The temperature is too high.
  • Infrequent waterings.

What Are The Signs Of Underwatering?

Underwatering is not very common amongst growers but can occur when the medium doesn't retain water well or the temperature is too high, evaporating water fast. When there are signs of underwatering in cannabis, the plants will look lifeless and close to death, with their fan leaves facing down. This causes the root hairs will also begin to dry out, become thin and crisp at the tips, and the way the plants transpire will be severely affected.


How to fix over and underwatering: signs of underwatering

Fan leaves of your cannabis plant facing down are the symptoms of underwatering.

The leaves will become dry, crispy, and depleted, and the foliage will lose its shine and soft, waxy characteristic. The aroma of the plants will become reduced and begin to smell like dried fan leaves.

How To Fix Underwatered Cannabis Plants

Underwatered cannabis plants may seem lifeless but it doesn't take too much for them to recover. The key thing is not to overwater your plants but to feed them enough until you see the liquid run off at the base of your pots. It should take 30-60 seconds before there is a slow rate of water or nutrient solution forming at the bottoms. Keep the nutrient solution the same as before and do not attempt to increase the E.C level to try and make up for the lost time.

What To Remember

  • You should aim to saturate the growing medium until the signs of runoff.
  • The growing medium that is being used will have an effect on how much water is retained and how much is drained away.
  • Keep the temperature of your water around 15-22 degrees Celsius and avoid cold water.


How to fix over and underwatering: how to fix underwatering

When watering your cannabis plants make sure not to use cold water.

How To Avoid Underwatering

Avoiding underwatering is quite simple, you can avoid it by giving your plants just the amount they need, not a drop more or less. Even though underwatering not being as common as overwatering, it causes serious problems and can also result in plant stress. To avoid underwatering you shouldn’t let the substrate dry out completely, so watering when the growing medium is still damp is a good way to avoid it, don’t wait until the leaves are droopy because this is a sign that the growing medium stayed dry for too long.

Check the moisture of the substrate

Ideally, you should water your cannabis plants every 2-3 days but this shouldn’t be followed as a schedule but if your soil is drying in 1 day or less, you’re definitely underwatering. 


How to fix over and underwatering: how to avoid underwatering

If your plant doesn't look very healthy, it could be signs of underwatering cannabis.

To know when it’s time to water your plants you can use a soil moisture meter to be sure but if you cannot afford or find one in your local grow shop, you can go ahead and stick your whole index finger; If your finger comes out dry then it’s definitely time to water your plants, if not, you can wait a couple of days and check again.

Lift the pot

Another way to avoid underwatering if you don’t have a moisture meter is to lift the pot, to make it easier you can fill another pot of the same size with the same substrate mix you’re growing in, this way you can lift the pot and feel the weight and kinda feel how dry the substrate is, and know when you should water again, as mentioned above if you’re a beginner you should check this regularly and if the soil is drying out in less than a day, you’re probably underwatering.

Top Tips

  1. Any foliage that has become lifeless and crisp it should be removed from the plant. Dead leaves will attract insects and unwanted guests.
  2. After you have watered your growing medium correctly, wait until the containers are light enough to pick up before watering again.
  3. Outdoor growers who may not always be able to water their plants on time can benefit from using a pump and drip lines.
  4. Foliar feeding Cannabis plants is an excellent way to revitalize them, as well as saturating the growing medium. This will help restore the amount of moisture they can transpire.
  5. Cannabis plants grown in smaller pots will always dry out quicker, so it is a good idea to plant into a larger pot that can hold much more moisture.

3. The Importance Of Water Purity

As you may know, water is super important for cannabis plants because it’s used in a plant’s basic processes such as transpiration; Depending on the source, your water can contain trace elements that may end up affecting your plant and in some cases the symptoms may be similar to overwatering and underwatering so, if possible, you should check the pH and PPM (or TDS or EC) of the water, once you know your water is good, it will be easier to identify if you’re really dealing with any of the problems mentioned above.


How to fix over and underwatering: the importance of water purity

Water purity is super important because it may contain trace elements that result in symptoms similar to when overwatering cannabis.

Remember that this is not obligatory but if you don’t know if your water is okay, the symptoms may get you confused and you may be trying to fix a supposedly underwatered or overwatered that may have other problems such as pH problems or suffering from overfeeding.


Underwatered Cannabis Plants SymptomsOverwatered Cannabis Plants Symptoms
Thinning of the leaves.Droopy leaves.
Crispy leaves.Yellowish leaves.
Waxy appearance.Browning of the tips of the leaves.

4. Monitoring PH Levels

The very first thing that you need to consider when watering your cannabis crop is the pH of the water source. For new growers, this factor is often overlooked, but if you want to get the very best out of your plants then do not make this mistake.

What is pH?

The pH (power of hydrogen) is the scale we use to describe the acidity or alkalinity of any liquid or substrate. The midpoint of this scale sits at 7, with any value under 7 indicating an acidic solution and any above indicating an alkaline solution. Cannabis crops are quite picky when it comes to optimal pH levels, and this value changes throughout the life cycle of the plant, and with the different styles of growing. The pH value of the feed water has a direct influence on the ability of the plants to uptake nutrients. It is also important to keep tabs on the pH levels of the growing medium, whether that is soil, coco coir, or a full hydroponic setup. In general, we suggest new growers use coco-coir as their growing medium. Coco-coir offers many of the advantages of both soil and hydro cultivation and is a forgiving medium to work with.

For soil cultivation, a pH level of 6.0 to 7.0 is suggested. For pure hydro or coco coir grows the recommended pH is anywhere between 5.5 to 6.5. When feeding your plants, always do your pH check last. This ensures the levels are correct as the plants receive their feed, and you can also test the runoff water to make sure the substrate pH levels are correct. You can grab a pH meter from any reputable hydro supply store, or online. You don’t need to spend an arm and a leg but do not buy a really cheap one. This meter can make or break a grow. For all the info you could ever need on pH head over to our complete pH guide

5. Monitoring PPM Levels

Another important factor to keep in consideration when watering your crop is the PPM (Parts Per Million) of minerals that have dissolved into the water source. This is more important when growing in a hydro or coco-coir setup (where the medium is inert and all nutrients must be added) than when using a soil-based growing medium, but grabbing yourself a TDS (Total Dissolved Salts) or an EC (Electrical Conductivity) meter is still recommended no matter the cultivation style you choose.

These meters allow growers to accurately measure the nutrient and mineral levels in the feed water. Over and underfeeding, and nutrient deficiencies can be hard to differentiate between. Having a TDS meter can help with diagnoses, and is just a handy bit of kit to have on hand for any grower.

6. Using Reverse Osmosis Water

Source water is a tricky issue to tackle, as it varies so widely from location to location. Not all source water is created equally and depending on where you live, the tap water may contain pollutants or bacteria which are actually harmful to the progress of your crop. If this is the case, or you just prefer to start with an as inert a source of water as possible, then you may want to invest in a reverse osmosis filter.  By using pressure to force water molecules through a semipermeable membrane, a reverse osmosis filter removes close to 99% of dissolved salts leaving you with a totally clean palette. This gives growers much more control over exactly what the plant does and does not consume and can help with nutrient deficiency issues. While there are some cheap options on the market, in general, these are not the most budget-friendly machines. If you are looking to use RO water to treat growth issues you can also choose to purchase reverse osmosis water by the bottle which will bring the cost way down.

7. In Conclusion

If you are not familiar with overwatering or underwatering symptoms, or how responsive Cannabis plants are and have no control over the temperature and humidity levels of your grow room, then it is very easy to go from one extreme to another. Overwatering cannabis is very common so less is more when it comes to watering plants, and if you apply this as a rule of thumb, along with the correct pH levels, E.C, watering frequency then your plants will respond in kind.

12 May 2022