The saying “too much of a good thing” always comes to mind when talking about watering cannabis plants. Underwatering plants is a major risk that should be avoided, but overwatering can cause a heap of other problems. Spotting the signs of overwatering your weed early and knowing how to adjust is the only way to save a plant from a watery grave.
How much water do weed plants need?
The old saying when it comes to watering plants is that they need “Enough, but not too much”. If that sounds vague, congratulations, you’re paying attention. There’s no single magic number when it comes to watering weed which is why watering is so worrisome.
The amount of water that any weed plant needs varies based on its size, age, environment, growth medium, and even strain. Obviously, younger smaller plants will require far less water than a massive plant in full bloom. Check out our complete watering guide for all the details on exactly how much and how often you should be watering.
Dangers of overwatering
Many novice growers are so worried about underwatering (as they should be), that they go a little overboard. Overwatering plants can be just as harmful to your plant as underwatering and can be much harder to fix. If left unattended, branches can bend and snap under the increased water weight and will slow their growth considerably.
The biggest danger to a plant as a result of overwatering is root rot. Root rot occurs when the soil gets so water-logged it prevents the roots from getting enough oxygen. These roots will eventually drown, die, and begin to rot. Rotted roots prevent the plant from getting enough water, and the rot will continue to spread until the plant has died.
While it is technically possible to cure root rot, the time, energy, and risks involved are almost certainly not worth it. Instead, it’s much better to avoid overwatering in the first place—even if that means a little bit of underwatering.
Signs of overwatering cannabis
Overwatering doesn’t happen overnight. It can take a few days or even a week before you realize that something is wrong. By then, though, you might already be in trouble so knowing what to keep an eye on can save you a headache.
1. Wet soil
For starters, check the soil. If there’s any amount of pooling on the topsoil, then you’ve almost certainly given your cannabis plant too much water. If this is a one-time thing, then you’ll be fine; just skip the next watering. However, if this persists, then you don’t have adequate drainage and are hurtling towards disaster.
2. Droopy leaves
The most telling sign of an overwatered weed plant is limp droopy leaves. The leaves of a plant that have been overwatered are just too full of water that the plant can no longer support their weight and they will lose any degree of turgidity (stiffness) that they had previously possessed. Additionally, these leaves may have developed a bloated, almost firm feeling when pinched. You can feel the water held in there.
3. Slowed down growth
An overwatered cannabis plant will also slow down its growth considerably—possibly coming to a complete halt. This will be incredibly noticeable in the late vegetative or early flowering stages when cannabis plants are growing noticeably every day. As the roots struggle to get enough oxygen, the plant will stop growing.
4. Yellow leaves
Lastly, after several days of overwatering, the leaves may start to turn yellow. This is a result of the roots being unable to take up enough nutrients to keep the plant going. At this point, your plant is on death’s door and only emergency intervention can help save it.
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Overwatered or underwatered?
If the symptoms of overwatering (droopy yellow leaves, slowed growth) sound familiar, that’s because these are almost the exact same symptoms of underwatering. While these descriptions of the symptoms are, indeed, almost identical, the way that they present themselves is quite different and a trained eye can spot these differences immediately.
Since weed plants are as much 95% water, underwatered plants will lose their turgidity rather quickly. These droopy leaves might look like those from an overwatered plant, but the texture difference is night and day.
Overwatered plants have heavy leaves that are a little firm and just feel sodden to the touch. On the other hand, the leaves from underwatered plants are thin, flimsy, and maybe even crispy to the touch.
Even the coloring can give it away. Underwatered plants can start to turn yellow after a single day or two (depending on the size of the plant) as they immediately lose access to nutrients. Overwatered plants, however, take time to develop this yellowing. If your plant is droopy and yellow it’s likely underwatered. If it’s just droopy, it’s likely overwatered.
Again, the best thing to do if you’re unsure is to check the soil. Stick a finger about 2.5 cm in and check the moisture level. You’ll know right away which problem you’re dealing with.
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How to fix overwatering of weed plants
Fixing an overwatered plant is much harder than an underwatered one but it can be done—assuming you catch it early.
Step 1: Stop watering
It should be obvious, but if your plant has been overwatered, then don’t give it anymore. Depending on the size of your pot, it could take 3-5 days for the soil to dry out, so keep a close eye on things. If you caught your mistake early enough, this should be all it takes. Weed plants are resilient and a little excess water won’t kill them.
Step 2: Aerate the soil
Depending on the growing medium you’re using, this could be an essential step. Even though you’ve stopped adding new water, the soil you’re growing in will take time to dry out. If you’re using actual soil (dirt) then this will matter a lot more as it tends to retain water far better than something like coco coir.
The easiest solution is to get a spike of some kind and gently poke holes into the soil. Chopsticks, coat hangers, and wooden dowels all make excellent choices and are likely already something you have on hand. Slowly and carefully poke them into the medium being careful not to stir the soil too much. You don’t want to damage the roots.
Step 3: Use solid additives
Adding perlite to your soil will help to quickly draw out excess water. After you’ve made a few small holes in your soil, pour some perlite in them and sprinkle it around the top before very gently mixing the top layer of soil. The maximum amount of perlite that should be used is about one-quarter of the volume of soil in the pot, though you’ll likely want to use less since it won’t be evenly mixed.
Step 4: Transplant to new soil
This is an extreme solution and not something that we would recommend in most cases. First of all, the water-logged roots are incredibly fragile and are liable to be completely destroyed if this isn’t done properly. Additionally, even if you do manage to transplant the plant successfully, the damage is done.
The process here is no different than transplanting a healthy cannabis plant with one exception—wash the roots. If your plant is damaged enough to warrant a full re-potting, then root rot has almost certainly set in. If this is the case, then you’ll need to remove any damaged bits. Don’t skimp on this step; in for a penny, in for a pound.
After you’ve removed the damaged areas, gently wash the rest of the roots with clean water. Next, clean (or throw out) everything that touched that plant. Honestly, we would probably toss the pot and the solid and start fresh. Add the soil gently, making sure that the roots are somewhat spread out. This is likely a two-person job, so grab a friend.
If the plant was still in the early vegetative stage, then this might be worth it to preserve genetics, but if the plant was already flowering (or even just larger than 20-30 cm), then this is unlikely to be worth the hassle. Even if holding onto the genes of a strain is the goal, you’re likely better off taking clones and hoping for the best.
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How to prevent overwatering of cannabis
Like many aspects of growing, prevention is the best solution. By taking a few steps early, you can prevent overwatering from ever becoming a problem.
1. Monitor your watering schedule
Routines are good but they need to be flexible. Just because you should be watering every 2-3 days doesn’t mean that you have to. If the soil is still wet, don’t water. If it’s been 3 days and the soil still isn’t dry, then it’s likely an issue with either the environment or your drainage.
2. Control your environment
The ideal environment for growing cannabis is 22-28°C with a relative humidity of 65% (45% during flowering). This combination also allows for the optimal evaporation of water from the soil into the atmosphere. If your grow space is too cool or too humid, then the soil will hold onto moisture for longer than it should.
Additionally, the importance of airflow cannot be overstated. While external ventilation is important, so too is internal airflow. Keeping a good fan blowing inside of your grow space will help keep the soil from holding onto too much water and prevent pooling from the occasional overwatering.
3. Use fabric pots
While plastic might be the default flower pot material, fabric pots are typically better for growing cannabis. These pots allow for water to drain from the sides as well as the bottom, meaning that excess water can escape much faster. Combined with good airflow, fabric pots can save you from overwatering if you make a mistake.
Let’s water it down
Overwatering cannabis might be the easiest problem to prevent, but that doesn’t mean that it can be ignored. By keeping a close eye on your soil, you can make sure that your plants aren’t drowning.
- Disclaimer:Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.
Been waiting for this for years. And it came after three solid years of studying micro biology, growing conditions plus IPM reading virtually everyone of your grow reports you have written. However a massive thanks for your help on keeping us within the perimeters of growing a magnificent plant 🌱