How and when to give water to your cannabis plants

How and when to give water to your cannabis plants

Watering your cannabis seems like it should be the most straightforward form of plant care. However, this is actually the area where many growers make mistakes. Not through lack of trying, but due to an overenthusiastic approach. Here is a rundown of everything you need to know about watering cannabis plants.

The lifeblood of nearly all organisms on earth, water is vital for your cannabis plant’s survival. With that in mind, knowing when and how to water your cannabis plants is essential for keeping them in optimal shape.

Although cannabis will show resilience with a lack of, and in most cases, too much water, neither state should be prolonged. In doing so, growers risk poor bud production and stunted growth. In worse case scenarios, the lack of both water and nutrients could cause your cannabis plants to die.


The starting block of adequate watering; what time of day should cannabis be watered? Some sources say at night, while others say first thing in the morning. If you are a first-time grower, this conflicting information can be confusing.

For the vast majority of growers, watering in the morning is the preferred option. Once daylight or artificial light starts, cannabis plants will use the water and the nutrients provided to conduct photosynthesis, thus driving growth.

If there isn’t any water available when this process starts, cannabis will be negatively impacted—in the same way we would be pretty useless if someone asked us to start work without any food or drink beforehand.

As a general rule of thumb, water early in the morning if you are growing outdoors. If you have chosen to grow indoors, give your cannabis plants water when the lights-on cycle begins. This way you will ensure they have enough available to go through the most intensive part of the day.


Giving water to your plants

Douse the entire plant, liberally soak the soil, or spray a light mist? It may not seem like a big difference, but the technique you choose will dictate how much water to provide. The best method is none of the above. Ideally, for most natural form root development, water cannabis plants via bottom feeding.

By placing pots into a tray of water, the roots will draw what they need upwards through the soil. It also encourages your roots to grow downwards, which is beneficial for the whole plant.

If after 30 mins there is still water remaining, remove the excess. If there is no water left, add a little more to see if it is absorbed. Due to the unique process of osmosis, root structures will only ever take the water they need—nothing more, nothing less.

If bottom feeding is not an option, saturate your substrate by adding water to the top until you see it draining out the bottom. Do not water so much that a pool remains on top or the soil becomes muddy. You want to soak the entire substrate, but you’re not trying to drown it.

The water should generally drain away by the time you have moved onto the next plant/pot. Getting the amount of water correct can be difficult until you have a feel for how thirsty your plants are. Just stick to adding a little bit at a time until the water drains and you feel it is adequately hydrated.

Drip feeding water via an irrigation system is another method that is highly efficient. Although more challenging to set up, it takes a lot of the complications and risks out of watering by hand. We will cover the benefits of this method later.


Watering frequency is a slightly more complex variable. The rate at which you water will vary according to temperature, the strain’s attributes, whether it has begun to flower, and even the size of the leaves.

The easiest, all-around approach is to water every 2–3 days, depending on the soil and the intensity of your lighting equipment. Soil can dry out, and in reality, it almost should. If your soil or any other substrate you are using is permanently wet, this can encourage mold to grow and cause roots to die. 

Push a finger knuckle deep into your substrate to gauge how hydrated it is. If the substrate feels dry and your cannabis is not a vibrant shade of green, then watering is likely required. If, on the other hand, the substrate is still damp, hold off! Your cannabis will survive, and it is far easier to add water than it is to take it away.

Weight is another telling factor of whether your plants need watering. If you are growing in pots, pick up each container you intend to water. If it feels heavier than usual, again, hold off. There is still water present, so no further moisture is needed. As a point of reference, fill an empty pot with a substrate so you can compare the general weight of dry versus wet.


Adding nutrients

Adding nutrients to water is straightforward. Ensure you follow the manufacturer's guidelines and mix thoroughly. If you know the nuances of the strain you are growing, it is at this point you will alter any nutrient concentrations. When you are happy with the solution, apply to the soil as you would a regular watering.

Many anecdotal accounts like to see between 10–20% water runoff into the trays beneath the plants. The theory is that this will help prevent nutrient lockout from occurring. Just like with plain water, too many nutrients can be detrimental.


Straight from the tap is where most growers get their water. Assuming those same growers approach the rest of the variables of growing cannabis with absolute precision, it seems a shame that some do not think about the complications tap water creates.

Depending on your location, the mineral content of tap water differs wildly. This, when it comes to mixing nutrients, can make calculations tricky. A simple way to counteract the uncertain nature of tap water is to fill a bucket and leave it to rest overnight.

The following day, you should be able to take a more accurate reading, and in most cases, the water should be suitable for use. If you know you live in an area with incredibly hard water or high levels of sulfur, there are several testing kits along with chemical remedies to bring the water to a more stable composition.

Another benefit of leaving water to rest overnight is it will be at room temperature. Water that is too hot or too cold also does damage to your cannabis plants. 


Checking the ph value of water

Before testing the pH of your water, follow the step listed above and leave the water to rest overnight in order to reduce the eventual chlorine content.

Once you have done so, you will need the following: your water, pH up and down, a pH meter, and your nutrients. If you are going to use a watering can, then have that ready too. The solution mixed in the bucket should then be transferred to the watering can.

With all equipment in hand, your target pH for water should be 6.3–6.7 for soil and around 5.5 if you are using a hydroponics setup.

Add your nutrients and either the pH up or down until you get the correct reading. Just make sure to stir thoroughly for the most accurate recording.


As simple and dummy as it may sound it is quite important for plants to receive a solution within an optimal temperature zone.

Happily most of the growers do not run into problems of this nature, but consider this story as a lesson. One of our friend growers spent about 5 weeks last winter trying to figure out what was wrong with his plants.

He checked multiple alternative solutions, equipment, lightsource, altered the feeding schedules dramatically at some points to experiment etc; only until he realised that the tap water coming out of the wall had much lower temperature in the winter (15-17C) compared to the summer season (+25C).

He effectively drenched the plants with too cold solution making them stress more and more not being able to absorb neccesary nutrients. If your water/nutrient mix is below 22C, plants might not be able to absorb Phosphorus and other elements properly.


We alluded to this earlier, but drip watering via an irrigation system is the ultimate solution to “little and often,” waterings, allowing growers greater precision over how much water their plants receive. You will need to attach the irrigation system to a supply of water, setting up drip points at the base of each plant.

The entire system will be fed by the main supply pipe, which shouldn’t be any further than 50 meters from the water source. Drippers attached to carefully placed t-junctions along the main supply pipe will be responsible for providing the plants with water.

Follow the same principles as previous methods of watering, allowing the water to briefly collect on the surface of your substrate then drain away. Because the distribution of water is slow and controlled, it is far more difficult to fall into the trap of overwatering.

As drip feeding water is much slower, you will need to tweak watering times so that you start the process earlier.

When working with drip irrigation systems, remember to keep them clean and avoid knockoffs. Most problems occuring while working with drip system come from lack of proper maintenance and cheap equipment. Remember to clean the tubens and connectors on a regular basis to avoid them getting stuck and risking ruining your crops.


A wilted marijuana plant

Although it’s usually novice growers who make this mistake, overwatering is a difficult habit to overcome for many cultivators. Our desire to provide the best for our cannabis plants can make us overzealous with the resources it needs.

As well as water, roots need oxygen. If your root system remains drenched continuously, oxygen is unavailable, and your plants cannot grow. The cells in the roots will die and so too will the remaining plant structure.

What's more, excess water can lead to root rot, mold, and mildew, all of which will, again, kill your plant or harbor bacteria that will do the same, just over time.

Fortunately, overwatering is an easy mistake to spot, most of the time plant looks like its wilting while the pot is drenched with water; unfortunately, the only remedy other than waiting for it to dry out is to transfer the plant from one pot to another containing fresh, dry substrate.

If root rot has settled in, ensure you cut off all affected areas before replanting. Few companies offer solutions for root problems. In some cases beneficial funghi or symbiotic bacteria can help to avoid running into these problems.


Leaves will start to wilt and turn inwards, root structure will shrink, and plant structure will begin to bow through lack of strength. Left long enough, your plants will die without any water, just like humans, animals, and all other plants would. Without the nutrients provided by the water, all of the plant's natural processes like photosynthesis will slow or stop.

Prolonged periods of dryness will eventually cause permanent damage to your plant, resulting in stunted growth and poor bud production. However, short periods of drought are easily remedied by giving plants water in the “little but often” manner. When you are sure they are re-hydrated, regular watering cycles can resume.