Over-Watering Cannabis Plants

Overwatering and under watering your cannabis plants can cause multiple symptoms and may even slow down growth. It’s all about understanding your plants and finding a sweet spot. We explore how to recognize and fix these issues, as well as take a look at the importance of water quality in general.

There are many contributing factors involved when it comes to a successful and bountiful cannabis grow. Lighting, nutrients, airflow, and humidity all play important roles in optimal growth and vibrancy of a crop. Water, however, is one of the most important aspects of keeping cannabis plants healthy and strong.

Watering isn’t always as simple as it may seem. Many growers are under the impression that completely saturating their crop with water each day is all it takes to help plants obtain their aquatic requirements.

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The truth is, there is much more to the watering process. Watering cannabis plants is a balancing act that takes some time and experimentation to perfect. Too much water can lead to some serious problems for plants and may obstruct oxygen intake. On the other end of the spectrum, too little water can lead to extremely dry conditions that will leave cannabis plants thirsty, eventually causing them to wilt.

We take a look how to recognise if you are over or under watering, and how to fix it.


Overwatering is an easy mistake to make when growing cannabis, and is most likely caused by worrying that plants need constant doses of water. It is a pitfall novice often fall into.

Cannabis plants actually use their root systems to breath air, in addition to uptaking water, and if their roots are constantly swamped in water, they will begin to drown.

1. One primary symptom of overwatering is drooping leaves. However, it is not the same kind of droop you see when underwatered – where leaves look wilted. It is the opposite in fact. Leaves are so full of water, that they are being forced to curl in on themselves. It results in them becoming very firm.

2. Additionally, the rate of growth of overwatered plants will slow down dramatically or may even come to almost a complete halt. This is due to the anaerobic conditions that arise due to the lack of oxygen accessible to the root system.

3. Another symptom of overwatering a cannabis plant is yellowing of the leaves. This is a sign of a nutrient problem, that is a side-effect of overwatering.

If you are experiencing any of these symptoms within your plants and believe the root cause is overwatering, the best thing to do is water less often. Wait for the top layer of soil to look and feel dry before watering again. A good test is to put your index finger in the soil up to the knuckle. if it is dry, consider watering.

Also, make sure each plant has adequate drainage and that water isn’t building up too much in the bottom of the pots or containers that they are housed within. You want excess water to drain out of the containers, leaving soil moist but not waterlogged.


1. Underwatered cannabis plants will look very weak, lifeless, and will show signs of wilting. Its no wonder they begin to look this way considering the vital role of water in plant physiology. The wilting of underwatered cannabis is different from the plump curling of overwatering – even if only subtly. Leaves will be fragile, brittle and even papery. They will look lifeless and drab. Another sign of an under watered cannabis plant an extremely dry growing medium, such as crispy soil.

2. Underwatering occurs when growers simply aren’t meeting their plant’s demands. Without adequate water, the root system will dry up and growth and yield may be reduced. Be sure to water your plant when the top inch of soil has dried out. Leaving it any longer than this may start to have detrimental effects.

3. One aspect that may cause underwatering is not using the correct pot size at certain stages of growth. For example, growing a small seedling in a large pot may reduce the plant’s chances of uptaking enough water, as the small root system doesn’t have a chance to uptake water before it drains away.


As well as watering frequency, the quality of the water used to supply a cannabis crop is also a highly important consideration.

Cannabis plants consist of approximately 90% water, and the substance is required during various vital physiological process such as photosynthesis and transpiration. When using a poor quality water source to supply cannabis plants, these processes may be less efficient than they can be, or in worst case scenarios, disruptive.

When these disruptions occur, symptoms may manifest that appear almost identical to an array of other conditions such as over or under fertilisation, under-watering, and possibly even heat stress. This is a perfect example of why to always double and triple check the root cause of the problem when troubleshooting health issue of cannabis plants.

5 Surprising Signs of Overwatering

1.) Brown Leaf Edges

When I first started growing cannabis I heard this symptom was nutrient burn (too many nutrients), but since then I’ve learned nutrient burn typically only affects the tips of leaves as opposed to all the edges. I’ve also heard this is a calcium deficiency, but that looks more like brown patches or burns on the leaves themselves. I’ve peresonally found that spots on the serrated edges of leaves are often related to root problems or issues with water movement through the plant. Most commonly overwatering.

Overwatering can cause brown spots on the serrated edges of leaves

Over-Watering Cannabis Plants

These brown leaf edges appeared after the plant was heavily watered

Over-Watering Cannabis Plants

How can you tell the difference between brown leaf edges from overwatering vs nutrient burn? The burnt spots appear on different parts of the leaf.

Over-Watering Cannabis Plants

2.) Yellowing or Bleaching

Overwatering prevents plants from conducting normal plant processes. A heavily overwatered cannabis plant (especially a young one) may start looking yellow all over from being overwatered. The yellowing can occur even when roots have access to nutrients and are given the right pH.

This seedling is yellow all over due to being overwatered in a big pot with a thick grow medium

Over-Watering Cannabis Plants

Here’s another example of an overwatered seedling that’s turned yellow all over

Over-Watering Cannabis Plants

Overwatering can also cause symptoms that look similar to light stress because you may see the top leaves close to the light are turning yellow. Although it looks like light stress (a sign the grow light is too close), the issue is actually that the plant isn’t able to move water and nutrients properly. The plant can’t keep up with the hardest-working leaves and they start turning yellow. If you know you’re keeping your grow lights the right distance away and are still seeing yellow top leaves, there’s a strong chance you’re actually dealing with a nutrient deficiency or a watering problem.

This seedling turned yellow on top after the roots were too wet for too long

Over-Watering Cannabis Plants

3.) Cupping or Curling

Sometimes the symptoms look a bit like heat stress (tipped edges, curling up or down, etc.). Since overwatering is relatively common with heat, this can keep you focused on the temperature when you should also be paying attention to watering habits.

The top leaves curling down, yellow bottom leaves curling up, and stunted size are all signs this seedling is suffering from watering problems

Over-Watering Cannabis Plants

The following seedling looks green and mostly healthy, but notice the soaked grow medium and top leaves are curling down. This indicates seedling is being overwatered.

Over-Watering Cannabis Plants

The grower didn’t realize she was overwatering, and the symptoms kept getting worse. Okay, I’ll admit it was me, but this was a long time ago 🙂 Soon the leaves became wrinkled and papery with the edges folded up

Over-Watering Cannabis Plants

Another overwatered seedling showed a different sort of curling and cupping. I’m thankful for this batch of seedlings because I learned about some of the odd leaf symptoms that can result from overwatering!

Over-Watering Cannabis Plants

This stunted 27-day old seedling is growing slow with curling leaves as the result of being overwatered in a large container

Over-Watering Cannabis Plants

Notice the tips of leaves curling on this next plant. This is the result of overwatering combined with cold. Cold temperatures make it more likely for plants to suffer from overwatering because plants don’t drink as much. You can tell the brown tips are not nutrient burn (though it looks similar) because the browning appears in between the veins instead of just on the very leaf tip. The issue was also localized instead of all over the plant. That lets you know you’re looking at a nutrient deficiency as opposed to nutrient burn. Since this plant was receiving perfect nutrients and pH, that narrowed the problem down to overwatering. Once the plant stopped getting watered so much at a time, the leaves started growing green and healthy.

Over-Watering Cannabis Plants

4.) Topsoil issues

When it comes to diagnosing your sick plant, examining the topsoil can help you narrow down the possible problems. If you notice the following issues with your topsoil alongside any of the plant symptoms above, you can feel pretty confident that overwatering is your villian.

  • Fungus gnats
  • Green algae
  • Soil is constantly wet or waterlogged
  • Topsoil has turned solid
  • Indents or divots where water is getting poured heavily

Notice how the grow medium here looks completely soaked with green algae growing on top. Green algae only grows when topsoil is staying wet too long. That lets you know the problem is overwatering in this case without even looking at the symptoms on the plant itself.

Over-Watering Cannabis Plants

Just like algae, fungus gnats can only live when the topsoil is staying wet for long periods of time. If you see fungus gnats (tiny black flies buzzing around the soil) it almost always means you’ve been overwatering the plants.

This plant has a bad infestation of fungus gnats, which means it’s being overwatered. At this point, it’s hard to tell whether the fungus gnats or the overwatering is directly causing the symptoms, but the solution is the same: better watering habits.

Over-Watering Cannabis Plants

It’s common for topsoil to look hard and almost solid if it’s staying too wet for too long. If you’re also seeing green algae and permanent deep divots/holes where the water is getting poured, you can feel pretty certain you’re overwatering

Over-Watering Cannabis Plants

How to Fix Over Watered Cannabis Plants


Stop watering and let the plant dry out. Not completely( this will damage your roots) but close to it.


Go longer in between watering


Stop watering so often (this is usually the cause).


Place a towel or newspapers or flyers under the pots drain holes to soak up excess water after all the runoff finishes.


May need to drill extra drainage holes in pots with soil if not getting proper runoff.


Make air holes in the top of soil or coco coir with chopsticks (beware you open the gates to gnats).


Increase the heat slightly in the grow area a degree or too.


Bring in an extra fan.


If growing in soil remove from current pot and place into a slightly bigger and or same size pot or fabric pot to aid in drying it out faster to save the plant.

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