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Watering Your Cannabis: How To Fix Over And Underwatering

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.

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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.

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 YOUR PLANTS

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.

UNDERWATERING YOUR PLANTS

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.

WATER QUALITY IS PARAMOUNT

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.

HOW OFTEN DO YOU NEED TO WATER YOUR PLANTS?

This question actually has many different answers, as many different variables are at play. For this reason, there is no exact answer. For example, temperature, humidity, and other environmental factors can all change how often water will be required.

However, there are telltale signs that will display it’s time to once again water your plants. Checking the top inch of soil is a promising way to identify this. Wait for this section of the soil to be dry before watering again in order to avoid overwatering. Once you have done so multiple times, you should start to figure out how long it takes in between each watering, and then you can go by that length of time instead.

Paying close attention to your plants leaves is another way to tell if its time to water. Of course, waiting long enough to symptoms to arrive is not optimal, but any signs of wilting should immediately be followed by a dose of water.

MONITOR PH

Before the growing process, check the quality of your water source. One important factor when it comes to water quality is pH. pH is a numeric scale used to measure the acidity or alkalinity of a solution, with the middle value of 7 representing neutral. Numbers less than 7 represent acidity and numbers above 7 display alkalinity.

PH that is either too high or too low can cause problems in cannabis plants, as the pH of the water source can dictate a plant’s ability to absorb nutrients. Too low or too high pH water can affect the pH of your grow medium over time, which results in symptoms that look identical to those caused by certain nutritional problems.

Cannabis plants tend to thrive at a pH of around 6.5. pH can be measured extremely easily by simply applying a pH metre around a water runoff sample. Runoff is water that drains from your grow container, having passed through your grow medium. If the pH is either too high or too low, pH up and down products can be used to return it to normal levels.

PPM is another important factor when it comes to water quality. Ppm, or parts per million, is a method of measuring the amount of minerals that have dissolved into the water source being used. So, a reading of 90ppm will indicate that there are 90 milligrams per litre of minerals present within the water source.

Being aware of the PPM within water allows growers to avoid giving their plants too many or too little minerals. A lack of minerals may lead to deficiencies, whereas too many may cause burning to occur. Cannabis plants prefer a ppm of around 500 when in the vegetative phase, and favour a ppm of around 1000 during the flowering stage of the grow cycle.

TDS meters, devices that measure total dissolved solids, can be used to measure the ppm of a water source.

Monitoring ppm is quite advanced, and while useful, is not essential for novices finding their feet. Just bear it in mind as you look to expand your knowledge and skill.

REVERSE OSMOSIS WATER

Although the total dissolved solids within your water profile might be adequate, not all substances within a water source are beneficial for your cannabis crop. Water might be contaminated with other factors such as pollutants and bacteria. Reverse osmosis filters are a great option to almost completely remove everything within a water source, allowing growers to add back only what they want their plants to come into contact with.

Reverse osmosis filters are capable of removing between 95-99% of dissolved salts within a water sample and is therefore a standard method of cleaning water on an industrial scale.

Once again, using reverse osmosis water is an advanced growing technique.

With the above in mind, you should be well on your way to understanding how over and underwatering affects your plants – as well as overall water quality in general.

TESTING YOUR WATER RUNOFF

To produce healthy plants, you need to keep a close eye on the amount of nutrients your plants are receiving. To do this, use trays to catch the runoff when you water your plants, and analyse both its pH and PPM (parts per million).

WHAT PH SHOULD YOUR RUNOFF BE?

Cannabis plants tend to thrive at a pH of around 6.5. To check your pH, simply test the runoff using a pH meter. Our pH tester by Hanna Instruments is super simple to use and offers fast and accurate readings. If your pH is either too high or too low, you can use pH regulators to bring it up or down.

Too many fertiliser salts can obstruct nutrient uptake and cause wilting. Use the DiST 4 Pocket Conductivity Tester for accurate readings.

Too many fertiliser salts can obstruct nutrient uptake and cause wilting. Use the DiST 4 Pocket Conductivity Tester for accurate readings.

We explore how to recognise and fix cannabis over and underwatering, as well as the importance of good quality water.

Under-watering

Problem: If your plant is drooping, then it’s usually a sign of either over or under-watering.

Cannabis Underwatering Symptoms

  • drooping (plants often get better after being watered)
  • leaves often seem “papery” and thin because they don’t have any water inside them. (This is opposed to overwatering where the leaves often feel bloated and “fat” from all the water contained inside)
  • chronic underwatering eventually leads to yellowing leaves and nutrient deficiencies

If your soil or soilless medium looks bone dry every time you water, or if you know that your roots have dried out, than skip right down the the solution section, as you definitely have a case of underwatering.

Under-Watered Cannabis Seedlings – Leaves feel papery and thin, growing medium is dry

If it gets worse….

The marijuana plant in the middle is under-watered, causing it to droop. Because it was taller and directly under the grow light, it became underwatered even though it was getting the same amount of water as its siblings. Sometimes you’ll see signs of under-watering immediately after upgrading your grow lights (if you don’t change your watering habits), because all the plants start drinking more due to the extra light and heat.

Chronic Under-Watering (Under-Watering on a Regular Basis)

Most growers tend to give too much – not too little – water to their plants. However, if you’re spending long periods away from your marijuana plants or the containers are drying up in less than a day or two, it may mean that your plant needs to be watered more often, or be given more water at a time.

It’s also common to under-water when plants start overgrowing their pots, or if growers get on a schedule of giving a specific amount of water as opposed to paying attention to the soil.

  • plant may need to be watered more often
  • plant may need more water at a time
  • plant may have overgrown its pot and need to be transplanted

It can be difficult to diagnose chronic underwatering because problems may look like nutrient deficiencies. One big clue is that plants perk up every time after you water.

Chronically Under Watered Seedlings – These yellow leaves are actually caused by the plants being slightly under-watered on a regular basis

The curling/clawing and burnt tips on the following two plants may look like it could be caused by another problem, but in this case the symptoms are the result of the plant being regularly under-watered

Notice how the leaves are clawing and tips appear burnt alomost like nutrient burn. It’s happening because the plant isn’t getting enough water on a regular basis.

The leaves near the buds of this male cannabis plant started turning yellow. In this case, the grower determined it was because the plant had overgrown its pot and was drinking more than expected, and as a result the soil was getting too dry between waterings.

More examples of under-watered cannabis plants

Extreme underwatering on a big plant

Not Sure? If you’re not sure whether your plant needs more or less water, how do you figure out exactly why your plant is drooping?

1.) Determine: Is my plant over-watered?

A cannabis plant does not get over-watered because it’s given too much water at once – overwatering is caused by the plant being watered too often, or if the plant does not have proper drainage (which means the growing medium is taking too long to dry out).

2.) If not over-watered, does my plant have root problems?

Growing hydroponically? When you see signs of wilting and overwatering in a plant that is growing hydroponically with the roots in water, usually that’s a sign of a root problem like root rot.

In fact, all cannabis plants can sometimes display wilting/drooping symptoms that are actually the result of root problems.

3.) You may be seeing symptoms of under-watering

So if you read the short description in step 1 about what causes overwatering (and you’re sure you haven’t overwatered your cannabis plants), and you’re certain you’re not seeing signs of root problems, than your cannabis plant might be drooping or wilting because it needs more water.

If you’ve been underwatering your plant, its leaves will look limp and lifeless, like these plants.

Symptoms of underwatering look the same whether your cannabis plant is growing in soil or a soilless growing medium like coco coir or perlite.

Solution:

Don’t wait until leaves droop to water your potted cannabis plant! While it is generally a good idea to let your potted cannabis plant dry out a bit after watering (watering too often causes its own problems), you should always water your cannabis plants again before the leaves start drooping.

This is the case for cannabis plants grown in both soilless growing mediums and soil.

First-time growers tend to overwater their plants, but underwatering happens too.

So you’re pretty sure your plant is under-watered. A thirsty cannabis plant will usually perk up quickly after the roots are given water.

Learn about ones of the best ways to properly water your potted cannabis plant every time…

How to water cannabis properly (for soil and most soilless mediums)

Wait Until Plant Needs Water – Wait until the top of the growing medium is dry about a half inch deep (up to your first knuckle). Preventing the topsoil from staying wet for long periods of time can also help prevent bugs like fungus gnats. Some growers prefer the “lift the pot” method to figure out when plants want water, where they actually lift the plant to see if it feels light from lack of water. Some non-soil growers, especially in coco or a very high-drainage growing medium, may water a little earlier when the top is just starting to dry out because it’s more difficult to overwater plants in that type of environment. If you continue running into problems with underwatering, you might consider watering more often than is generally recommended. It may be you need extra watering due to small pot size, rootbound plants, temperature, humidity, etc.

Water until you get a little runoff. If using nutrients in the water, add water until you see 10-20% extra runoff water drain out the bottom of your pot. This helps prevent nutrient buildup in the soil and if you have good drainage this type of watering schedule causes plants to grow faster than if you don’t water to runoff (it also makes it much harder to under-water your plants). If not using added nutrients (plants getting all nutrients from the soil, for example in a super soil setup), then only water until you get just a tiny bit of runoff out the bottom, so you’re not washing out your nutrients. However, you still want to make sure you’re saturating your medium – you don’t want dry spots in the soil!

Go back to step 1. If water does not come out quickly or pots take more than 5 days to dry out for step 1, you may have a drainage problem or need to give less water at a time until your plant is drinking more. If pots are drying out in just 1-2 days, you may need to give more water at a time, or transplant to a bigger pot.

A simple way to tell if a potted plant is ready to be watered is to pick it up and tell if it feels heavy or not.

As plants use up all the water in their pot, it will get lighter. If you need something for comparison, you can get an extra pot and fill it with your growing medium. Now you can use this extra container for comparison with your potted plants as it represents the ‘dry weight’ of your growing medium. If you pick up a potted plant and its feels just slightly heavier than your dry pot, then you know it’s time to water your plant. After a while you get a feel for how heavy your plants need to be and you may not even need the extra pot anymore.

Need more help?

If your plant is experiencing “the claw” and not just normal drooping (the ends of leaves are curling like a claw or pointing down like talons), then you may actually have a nitrogen toxicity (too much nitrogen).

These Plants Are NOT Over or Underwaterd, These Leaves Show Signs of
Nitrogen Toxicity
(“The Claw”, tips bent down, curling / clawing, dark green leaves)

From wilting to dropping to yellow leaves to nutrient deficiencies, under watering cannabis can cause a lot of unexpected problems and symptoms. Learn & fix!