Cannabis Cultivation

How To Water Cannabis Plants

Watering Cannabis Plants

Watering cannabis plants can be tricky sometimes. Like all plants on earth cannabis needs a good water supply to grow healthy. Knowing how much to water your marijuana plants takes skill and experiences. Some cannabis strains need less water, while others can require more water to grow correctly. When the plant needs water, it also brings up cannabis nutrients into it leaves and flowers. This makes it even more important to make sure you get watering right for your plants.

Cannabis also needs different amounts of water as it matures and grows over it’s life span. There is now exact plan when it comes time to water cannabis plants. In this article you will learn how to water cannabis plants the right ways and how to tell when and how much water is needed.

Water Cannabis Plants Infographic

How to know how much Water Cannabis Plants need?

There are so many factors that go into watering cannabis, most grows starting out think I just need to dump some water on the plant everyday and everything will be fine. However, this is not the case at all. Knowing how much water you need to using in your pots depends on the type of cannabis growing medium, you happen to be using for your growing needs.

Some mediums like Coco Coir and Peat Moss can hold far more moisture than soil, and therefor will not need water as often. Under or overwatering can cause many issues with your plants. Most growers don’t realize this, are run into all kinds of misdiagnosed issues. Some of them can be nutrient deficiencies, many types of plant diseases. On the other hand, not giving the plants enough water can also cause many of its own issues, up to and including death of the plant itself.   

Approximately how much water cannabis plants need will depend on these things:

  • What stage the plants is in its growth cycle
  • The Temperatures in the grow room or outside
  • The Size of your plant
  • How much Water the plant is getting naturally (Outside only)
  • Where the plant is located (if the plant is in the shade outside, or in front of your main fan indoors)
  • The size of your plant pots, or if it is directly in the ground outside
  • Type of growing medium you are using to grow the marijuana plant in

How to tell if your Cannabis Plant is Overwatered?


One of the easiest ways to check your plant for over watering is to do something we call the “lift pot method” of checking for over watering.

This method involves manually lifting the pot when it is dry. When the pot is dry you will know how much weight it has, compared to how much it weights when fully watered. There should be a natural progression of the plant pot from a heavy fully watered state to a light needing water state.

Each day gently lift the plant pot and check its weight, is it as heavy as yesterday when it was watered? If so, you know there is no need to water the plant at the time. Keep this routine up every day until that plant pot is light, and at the state of weight that it will need water once again. Using this method, you will be sure that your cannabis plant is never overwatered again.

Importance of Water Drainage Holes in Pots

You never want any access water sitting in the bottom of your cannabis growing pots. It is very important to have pots that allow for good drainage out the bottom and sides of the pot. Not having and pot drainage can have negative effects on the roots of the plant.

The Plant will show signs of overwatering

Your plant can also show signs that it is being watered too much. When this happens, the plant will start to droop from top to the bottom of the plant. Sometimes the marijuana grower will confuse this drooping with the plant needed more water. This only will compound the issues as the grower will give the plant even more water.

If the plant is starting to droop and you lift the pot, the pot is heavy like it is just been fully watered then you know that the cannabis plant has been overwatered and you will need to let it dry more.

Why does the Plant Droop when it has too much water?

For the plant to grow healthy and thrive, the roots require oxygen, the same as the top of the plant needs CO2. When the plant is flooded at its roots with too much moisture it can’t take in the oxygen it needs at the root level. This causes the rest of the plant to droop, until the roots are able to access the oxygen they need in the growing medium.

How to tell if your Cannabis Plant is Underwatered?

There are a couple ways to tell if your cannabis plant is in need of more water. The first one is described above. You can check the pots weight if it is light, then this normally means there is not much moisture in the growing medium.

The second way to tell is to use the “finger in the top of the growing medium method”. With this method you take your finger and push it down into the top inch and half of the top soil medium. If the growing medium feels dry at the top of your finger you know it will need some water. If you feel moisture then it will be best to wait and try again the next day until if feels dry.

How to water Cannabis Plants at Different Stages of Growth

When you water cannabis plants they will require different amounts of water for different stages of their growth cycle.

Germination: Cannabis plants require the least amount of water during the germination stage of growth. In fact, you will require no water at all when germinating your cannabis seeds. Using large amounts of water at this stage can cause your marijuana seeds to rot and die. Only keep your growing medium damp while germinating cannabis seeds.

Seedling Stage: This stage of growth also requires very little water. Giving too much water to the young cannabis seedlings can cause something called “Damping-Off” and is a fungal disease that grows around the base of the seedling. Once this fugus takes hold on the plant it will cause the plant to topple over and die. Only water once again as needed for this stage of growth.

Vegetative Stage: This stage will start to require more water for the plant to grow. The plant will start to up take more water each day. The grower will be required to check the plant daily buy lifting the pot and using your fingers to check the growing mediums moisture.  It is still very important not to over or under water your plants in the vegetative stage of cannabis growth.

Flowering Stage: After a couple of weeks into flowering is when your cannabis plant will require the most amount of water. It will be taking up more nutrients, as well as water to supply the plant while making flowers and seeds. Your plant will use more water during this time of growth, and this is the most important time.

Water Cannabis Plants
Cannabis Plant Needs Water

How to Water Cannabis Plants the Right Way?

Watering a cannabis plant can be a bit tricky to master. The first thing a grower will do is gage how dry or wet the plants growing medium is using the information documented above. Once the grower has decided how dry the cannabis plant is, they will need to add a certain amount of water to it.

Once the grower has determined that the plant is in need of water it is important to soak the pot very well. Many times, if the pot has dried a number of times the medium with pull back from the sides of the pots. If this is the case the water that is added may just run down the sides of the pot never soaking into the medium itself.

If this happens it is best to water the plant slowly making sure to only add a bit of water at a time. Then when that water has soaked well into the medium repeat the process.

Soaking the medium is important as the medium could have “dry spots” in it where the water is not getting to the roots on a constant basis. Dry Spots can cause root death in that area of the pot. Once those roots die it will affect the health of the plant overall.

Cannabis Roots are Hunting for Water

Cannabis roots grow deep into the soil outdoors, to find water. For ever inch plants tap root goes into the growing medium, it will grow the same height above the ground. As the plant grows larger the root zone will also expand, for this reason you can also expand the size of your watering area around the plant.

Catching Run off Water from your Watered Cannabis Plants

It is a great idea to use water catching trays under your plant pots in an indoor environment. This is a great way to make use of any access water that was not absorbed by the medium while you water cannabis plants. You can place the trays directly under the pots to catch any water the runs out the drainage holes. Many times, if you leave the standing water, it will use wicking action and get pulled back up into the medium.

However, if this happens it is important the water no sit in these trays and longer then 30 minutes. If the water hasn’t been wicked up by then it should be removed. Letting this water sit can cause other issues like root rot, mold, and cannabis pests’ problems.

Why Pot Size is important when it comes to Water Cannabis Plants.

Having the correct pot size for your cannabis in its different stages of grow is very important part when it comes time to water cannabis plants. Say a grower uses a 10-gallon pot for their cannabis plants that are only a week old. This young plant will only have a very small root zone with which to uptake water. The rest of the pot will have so much extra moisture that will be sitting there for weeks. Eventually the water will go stagnate, causing all kinds of issues for the plant roots. This wet soil is also a home for many types of cannabis pests like Fugus Gnats among other pests.   

On the other hand, it is also important to have larger pots for flowering cannabis. Budding Cannabis uses much more water than any other stage of growth. It will be important for the grower that the pot is large enough to hold the amount of water that the plant will need.

How to Check if you are Watering the Cannabis Correctly

The best way to tell if you are correctly watering your cannabis plants, is to check the roots. The grower can easily check the roots of the plant every time that it is transplanted into a new larger growing marijuana pot.

When looking at the roots, they should be healthy and strong white in color. It there are any roots that look dry and dead then it’s a good sign that the plant is being underwatered. On the flip side of this if the roots look brown, smell bad or rotten, and are not white and thick this can be a sign that you have been overwatering your cannabis plant.

Cannabis Plant Needs More Water

Using Water to Fix over Fertilization Cannabis Plant issues

Sometimes are a marijuana grower you will make a mistake of using too much salt-based fertilizer on your cannabis plants. When this happens, you can use a method called “Flushing”. What the means is that when you have used too much nutrient on your plant you are able to run clean fresh water though the medium to remove all the access nutrients that were added by mistake.

Flushing the plants with lots of water will rinse out the excess build up of nutrients. We recommend Organic forms of growing.

How to flush a Cannabis Plant

Take the plant and the plant pot with any area that has drainage. Next use a hose to water the plant for about 10 minutes making sure the water is draining out the pot and away from the plant. All this water will remove all the excess nutrient from the plant medium and wash them away, bring the medium back to a neutral state.

The Importance of Using a Quality Water Source

Having a good quality water source to water cannabis plants is essential for growing cannabis no matter where you live. If you don’t have access to an accessible, cheap and quality water source then growing cannabis can be almost impossible to do.

The first thing you will need to look at is if you are on well water or town water. Both these sources have their pros and cons for cannabis growers.

Things to look for in a Cannabis Water Source

When selecting a water source for your cannabis plant there are two many factors you will need to be aware of. First is the PH of your water. Cannabis needs a PH of between 6.5 and 7.0

Well Water Sources:


  • Cheap to use
  • No Chorine
  • Large Supply (Depending on where you live)


  • More likely to contain heavy metals
  • More likely to contain higher levels of magnesium, calcium, salts and nitrogen, iron
  • May have high amount of mineral creating “hard water” with a high PPM (Parts per Million of minerals)
  • count

City/Town Water Sources:


  • Usually have most of the heavy metals removed
  • Normally lower levels of Minerals and lower PPM’s


  • Normally costs money to use, can get expensive
  • Must remove chorine before use
  • Could be a limited supply for the town or city

As you can see there are issues with each one when you water cannabis plants. Both types of water come down in the end, to quality that you will be using.

The good thing is there are somethings you can do to improve the water quality. For example, a grower can use a reverse osmosis filter to remove the mineral salts in well water. This system is great for lowering the PPM’s of your well water making it safe to water cannabis plants with.

For Town or City water you can let the water sit over night or 24 hours. Doing so will allow the chorine to evaporate out of the water. You can then use this to water cannabis plants.

Other Types of Free Water Sources


Depending on where you live, there may be other types of water sources you can access for you plants water needs.

Rain Water (Our Recommendation)

Most places will get rain. As a cannabis grower you can buy a rain barrel and use it to collect the rain off your roof. Rain water is in our opinion the best source of natural water that you can use for cannabis cultivation. Rain water is free of heavy metals, free of excess minerals and has a neutral PH of 7.0.

If collecting rain water off your roof just be careful of bugs. Bugs can land on your roof and then drain down into the rain bucket. So, if using your water indoors to water cannabis plants be sure to keep an eye out for bugs.

Water from Brooks, Ponds and Streams

Growers can also use water from brooks and streams for outdoor plants. Cannabis growers can also use pond water to water outdoor plants. However, we don’t recommend that you use any of these water type indoors unless they are boiled first before using.

These types of water sources especially can contain bacteria, fugus, algae and even plant parasites that is unhealthy for marijuana plants and/or the medium. This is something you don’t want to risk bringing into the indoor garden as it will be hard to remove after the fact.

What is the best time to Water Cannabis Plants?

While the best time to water cannabis plants is when they need it the most or are dry. There are times of the day or lighting schedule that will be best for the plants.

When growing marijuana outdoors, the best time to water your plant will be just before dusk in the evening. This gives the water time to get down to the roots over night, and for the plant to take it up before the next important day of growth.

Watering indoors, it is best to water just before or right at the time the lights in your growing space come on. This is very important if the plant is in a warm summer grow room.

how to water cannabis

Cannabis Plant watering tips and tricks

  • When transplanting cannabis into bigger pots, add some water to the hole that you have made for the root ball before transplanting.
  • After transplanting angle, the growing medium slightly to the center of the pot with the cannabis plant’s stem directly in the center. This will help the water move to the middle where the root ball is, instead of running down the sides of the pots and out.
  • Buy a good kink resistant hose, so you don’t get holes in it when watering and have a flood or use excess water.

How to Water Cannabis Plants when your Away?

There are many automatic ways to water your plants in the market today. Some of these methods are better then others so we will give you our recommendations on the best ways to do this with having floods in your grow room while your away.

Hobby Marijuana Growers can give their plants a bath (Complete Free Method but requires a bit of work)

This may sound funny; however, you can fill your bath tub with some water. 2 or 3 inches depending on how long your will be away for. Next to avoid scratching the tub, lay a towel on the bottom of the tub in the water. Then sit the pots on the towel. The pots will wick up the water from the bottom drain holes while you are away, this can work for a few days to a week. Remember to put a light over them, while your away.

Buy Blumat Classic Automatic Self Watering System (Costs)

If you have never heard of Blumat you can buy them here. There only take a few minutes to set up and the plant will be watering themselves in no time. The water is drawn up from any watering container with a tube and then drips slowly over time into your cannabis pots that need water. Using Blumats your plants will water themselves while your out of town.

Cannabis Plant Watering Stakes

These are pretty easy to find at most dollar stores, or on Amazon. You connect a bottle to these stakes and as the plant pot becomes dyer while you are away the dry pot will wick the water out of the stakes that are stuck in the top of the pot. These plant stakes will water your plant for a week or so depending on how big the bottle you use with them.

Keys to watering cannabis image

Plastic Water Bottle (Easiest To do)

Take a used two-liter plastic pop bottle, take a sowing needle and make the smallest hole you can in the bottom of the bottle. Remember to make is as small as you can. Then fill the plastic pop bottle to the top with water. Take the bottle and set it on the top of the cannabis growing medium in the pot. While you are away the water will very slowly drip out the bottle to your plants. This will work for a few days to a week while you are away.

How Do Cannabis Plants Use Water?

Cannabis use water by bring it in from their roots though what is called Transpiration. Depending on how much humidity is in the grow space, the plant will release water from its leaves. The more humidity the less the plant will transpire, and the dyer the grow space is the more the plant will transpire though it’s leaves.

The interesting part of this is that the room humidity can play a big part in how much water and nutrients are brough up into the plant. When the plant is in very hot temperatures it will transpire to keep cool, much like humans do. When the plant is too cold it will stop transpiration altogether, cause it to have cannabis nutrient issues.


Much of how to water cannabis plants comes though knowledge and experience growing marijuana. We hope that this guide can help give you some direct if you have any issues with watering marijuana plants. Just always remember a little bit less water in the pots is better than a little more water in the pots! Happy Growing!

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