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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.

Over-Watering

Problem: After watering, your plants start drooping. Usually the droopy leaves will feel firm and appear curled down (the whole leaf will be curled, not just the tips, which is often a sign of nitrogen toxicity). With overwatered cannabis plants, you may also notice Chlorosis (leaf yellowing that is similar to a nitrogen deficiency).

Overwatered cannabis plants are droopy with leaves that curl down. As a result of overwatering, leaves often turn yellow or show other signs of nutrient deficiencies (especially when it comes to younger plants and seedlings!)

Overwatering does not always mean you’ve been giving the plant too much water. It can also mean that you’ve been giving the plant water too often, or growing plants in a growing medium that holds onto water without enough air, or doesn’t have good drainage out the bottom.

Cannabis plants use their roots to get oxygen, almost like they’re breathing. Oxygen is dissolved in water, and there’s also air pockets in their grow medium to provide a source of oxygen. When you water your plants too often, the roots end up sitting in stagnant water. The reason your plants droop is because basically their roots are starving for oxygen.

This sick marijuana seedling has several symptoms including droopiness and leaves with brown spots that appear to be a nutrient deficiency. Surprisingly, the true cause of both problems actually is the thick, wet, muddy soil.

The main sign of a cannabis plant being overwatered are the droopy leaves, though other symptoms often appear around the same time!

Overwatered Marijuana Plants

  • Drooping / Curling is the first sign of overwaterd marijuana plants
  • Plants start drooping soon after watering
  • Leaves are firm and curled down all the way from the stem to the leaf
  • Will eventually lead to leaf yellowing and other signs of nutrient problems if not corrected

The drooping cannabis plant below did not have drainage holes (water could not drain out the bottom of the pot). After watering the plant which appeared healthy the night before, the grower came back to this drooping plant the next day – this case of overwatering was caused by too much water being held near the roots due to lack of drainage:

Solution: The best thing you can do for overwatered plants is give them time between waterings, and then start off watering slowly until things seem back to normal. Make sure that water is able to drain easily out the bottom of potted cannabis plants. Be extra careful with small plants in big containers.

How to Water Cannabis Properly

Wait until the top of the growing medium is dry about an inch deep (up to your first knuckle).

Add water until you see some at least 20% extra runoff water drain out the bottom of your pot. Go back to step 1.

If top of growing medium stays wet for a long time, you may need to give your plants less water at a time, or improve your drainage.

The goal is to be watering your plants every 2-3 days. If it needs longer to dry out, you should be giving less water at a time. If it’s drying out too quickly it should get more water at a time (or may need to move to a bigger pot).

Some growers also use the “lift the pot” method to decide when to water your plants (basically wait until your pot feels “light” since the plants have used up all the water). It’s up to you to decide what’s easier for you.

If your plant medium seems to stay wet for a long time (more than 4-5 days or so), you may need better drainage. This also can happen when growers put tiny plants in a pot that’s way too big.

This cannabis plant has green healthy leaves, but as a result of overwatering it’s stunted and small even though its more than a month old.

Make sure that water drains freely from the bottom of your container (it’s recommended that you provide enough water to get at least 20% extra runoff every time you water your plants as long as your plants are drinking well).

You should see water coming out the bottom within a minute or two after watering. Then don’t water your plants again until the soil is dry up to your first knuckle.

If your plants are already overwatered, you can try to increase the temperature and airflow to help the water evaporate more quickly. You can also use a pencil to gently poke some air holes into the growing medium to provide extra aeration and oxygen to the roots.

Whenever a seedling has droopy leaves, it means that the roots are either not getting enough water (underwatered) or not getting enough oxygen (overwatered). This seedling has been chronically watered too often, preventing the roots from getting enough oxygen. As a result, the seedling has stayed small and mostly stopped growing.

For your individual growing medium and environment, your watering method will vary, but if your plants are drooping and you’ve been feeding them a lot of water, it’s a good idea to cut back and see if that helps.

Sometimes plants will be droopy no matter what you do, and the true cause is the plant is rootbound and needs a bigger container!

If you’re growing hydroponically with your marijuana roots directly in water and you see the signs of overwatering, that means you have a problem at your roots. Either your plants have root rot which is preventing them from getting oxygen at their roots, or you are not dissolving enough oxygen into the water (you can easily increase the dissolved oxygen in your water with a quality air pump and a few air stones).

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 Overwaterd, These Leaves Show Signs of “The Claw” which usually indicates a Nitrogen Toxicity
(“The Claw”, tips bent down, curling / clawing, dark green leaves)

Overwatering and underwatering cannabis plants are easy to do and can cause multiple symptoms including slow growth. Learn to recognize and fix these issues.