Watering cannabis plants seems like the easiest thing to do, yet many growers, especially those new to cannabis cultivation, make mistakes with watering. Overwatering is one of the most common reasons for all sorts of growing troubles such as nutrient deficiencies and cannabis diseases, although giving your plants too little water can also negatively affect their growth.

HOW MUCH SHOULD YOU WATER CANNABIS?

One issue with watering plants is that it isn’t really an exact science, and many different factors contribute to how much you should administer. As an obvious example, as your plants get bigger, their watering needs will change. But there are other, more complex variables that also determine how much or little you should drench your plants. Let’s discuss some of the most vital:

STAGE OF GROWTH

Unsurprisingly, the water and nutrient requirements of your plants will change as they grow and develop. A young seedling will take up much less water than a vigorous flowering plant with a large root system. This could mean that you water a small plant every 2–3 days, as opposed to once per day with a rapidly maturing plant.

GROWING MEDIUM

The type of growing medium you use largely determines how much water the soil can hold, and drainage plays a huge role in how often/how much you water your plants. Cannabis likes rich yet airy and “fluffy” types of soils that are well-draining. As another consideration, the growing containers themselves must have holes punctured in the bottom to allow the water to escape. More compact soil mixes will hold moisture much longer, so they require less frequent watering as a result. Otherwise, moisture can linger in the soil for some time, which can lead to nutrient deficiencies, root rot and fungus, pests, and a whole lot of other problems.

Here is a quick way to check if your water is draining properly: If it takes several minutes for water to drain after drenching the soil, and/or if it takes longer than 3–4 days for your soil to dry out, it’s likely that you have a drainage issue. Even if you don’t see adverse symptoms now, it could definitely lead to more problems down the line. In this case, you can add perlite or something similar to your soil to aerate the mix and improve its drainage ability. Perlite ensures that water doesn’t stay too long in your pot. The key to good soil for cannabis plants, whether store-bought or homemade, is to balance moisture retention with water drainage. This usually means soil that is dark and rich, but amended with perlite and/or other substances to promote a healthy and efficient medium for plants to grow.

HOW MUCH SHOULD YOU WATER CANNABIS? 

SIZE OF CONTAINER

Then of course, the dimensions of your container will also affect the overall balance between moisture retention and drainage. If you have a tiny plant in a huge pot, drenching the whole substrate is going to drown the poor thing before it gets a chance to flourish. Similarly, you might experience the opposite issue with huge root-bound plants stuck in minuscule pots. This is also the reason that growers normally start seedlings in smaller pots, then up-pot them later as the plant grows. A small seedling pot makes it much easier not to overwater the sensitive seedling.

OUTSIDE TEMPS AND LIGHT INTENSITY

Cannabis plants don’t always grow at the same pace. A plant in a cooler environment, for example, will grow much slower than one under balmier conditions. Light intensity plays another big role here. Plants that receive more heat and light are bound to have higher water and nutrient requirements than those with meagre light and chilly temps.

HEALTH OF CANNABIS PLANTS

The general health and vitality of your plants will also determine how much water they require. If growth is slow or stunted, or if a plant is afflicted with diseases or pests, it will likely not need as much water as one that is thriving.

HOW TO TELL IF YOUR PLANTS ARE THIRSTY

You now know about the factors that determine how much and how often cannabis plants need water, and how these factors can be different for everyone. So now, how can you tell exactly when you should water?

Here are some signs that your cannabis plants are thirsty:

DROOPING, WEAK PLANTS

If your cannabis plants are very thirsty, they will droop. The whole plant will appear rather sickly and lifeless, so it’s difficult to overlook this sign. One catch here though is that thirsty plants can look very similar to those that are drooping because of overwatering. The difference here is that the leaves of overwatered plants are usually dark green and form a “claw” where they curl and bend downwards, so the whole plant takes on a heavy and waterlogged appearance.

If you’re somewhat experienced, you should be able to tell these conditions apart. Most of the time, it should be obvious if the drooping is from over or under-watering: If the soil is bone-dry and you know you haven’t watered in quite some time, the sickly appearance of your plants is less likely from overwatering.

Tip: Know that slightly underwatering your plants is always better than overwatering. If you water thirsty, otherwise healthy plants, they should normally recover their appearance in a couple of hours. Occasional underwatering doesn’t usually have harmful consequences. Overwatering, on the other hand, is a silent killer.

DROOPING, WEAK PLANTS 

YELLOW OR BROWN LEAVES

Along with your thirsty plant wilting and drooping due to a lack of water, it may also display discoloured leaves in shades of yellow and brown. While it is perfectly normal for plants to develop yellow leaves during the final weeks of bloom, a healthy vegetating plant shouldn’t have any/many dry, yellow, or brown foliage.

JUST CHECK THE SOIL!

One of the easiest ways to check whether you need to water your plants is to get your hands dirty. There are two simple tricks here: First, stick your finger about 4–5cm deep into the soil. If it feels dry, it might be time to water.

An even better test is to lift up the entire pot to see whether it still feels heavy from the last watering, or if most of the water has drained away or evaporated. Keep in mind that to verify this test, you will need to know what your dry pot feels like as a reference. So keep this in mind as you lift/move your pots around.

HOW TO WATER YOUR CANNABIS PLANTS

Here is a simple rule: Water less often, but when you do, water well! So rather than giving your plants only a little water, but too often, drench the entire medium completely, but less frequently. But how much water is sufficient?

A full drench means watering the entire substrate with about half the capacity of the container in litres. So, if you grow in a 4l pot, give 2l of water or more. As we discussed previously, exactly how much depends on a lot of things. Still, you should see about 10–20% of the water that you gave coming out of the bottom as runoff. The runoff will also flush out minerals that accumulate each time you give water and nutrients, reducing the risk for nutrient lockout and deficiencies.

Tip: Do keep in mind that if you’re using certain media, such as peat, the soil can at first be very slow to absorb water, and may even repel it until well-saturated. This means that if you were to water the substrate all in one go, most would simply run down the sides of the pot and out through the bottom. In such cases, slightly “pre-water” your substrate and wait for it to soak in. After 10 minutes, you can give the rest of the water. If needed, repeat. Do the “pot lift test” in between to see whether the soil has really absorbed your water.

DON’T LEAVE YOUR PLANTS SITTING IN RUNOFF

Along with your containers featuring holes at the bottom for water to escape from, the containers themselves should be lifted slightly off the ground so that all the water can drain and plants aren’t sitting in stale liquid. Drainage trays can catch this runoff, but should immediately be dumped after collection to avoid creating a breeding ground for bacteria, pests, and mould.

HOW TO WATER YOUR CANNABIS PLANTS 

THE IMPORTANCE OF PH WHEN WATERING PLANTS

If you are growing cannabis organically in soil, you shouldn’t need to worry much about the pH level of your water/nutrient solution. But for the majority of cannabis growers who are using common mineral nutrients and grow weed in soil, coco, or hydroponically, the correct pH level of the water is very important.

The reason for this is that cannabis plants have a limited pH window where they are able to take in nutrients. If the pH level of the water is either too high or too low, the plants are unable to take in nutrients even if they are present, a phenomenon known as nutrient lockout.

When you grow in soil, the pH range of your water should be 6.3–6.8. If you grow soilless (e.g. coco) or hydroponically, the pH level needs to be even lower, 5.5–6.1. To test your water pH, use a pH measuring stick or pH measuring drops. If the pH is too high or too low, use some drops of “pH down” or “pH up” to adjust your water to the right level. Most of the time, if you’re using tap water, your pH will likely be too high. Also, if you’re adding cannabis nutrients to your water, measure the pH first, then adjust it after you add the nutes.

BOTTOM LINE—WATER WELL, BUT NOT TOO OFTEN!

If you know how and when to water your plants, and are aware of any associated issues along the way, you can prevent most common cannabis growing problems. You will raise happy, healthy plants, and can look forward to fantastic yields!

Happy growing!

PH Tester

HI-98107 pHep pH tester provides fast and accurate pH readings. The easy-to-use device is designed for non-technical users, and can help both novice and advanced growers measure water pH.

Buy PH Tester

Are you aged 18 or over?

The content on RoyalQueenSeeds.com is only suitable for adults and is reserved for those of legal age.

Ensure you are aware of the laws of your country.

By clicking ENTER, you confirm
you are
18 years or older