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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.

Overwatering vs Underwatering Marijuana: How can I tell if my droopy cannabis plant is over or under-watered?

A common question for new cannabis growers is how to tell if your drooping cannabis seedling is over or under-watered. It’s common for new growers to overwater their weed, but that doesn’t mean that underwatering doesn’t happen too. Never fear, once you get a feel for it, it’s easy to tell how often you should be feeding your plant and what is the true cause of your drooping.

If your marijuana shows signs of drooping in normal temperatures, it almost always means you’re over or under-watering your plants, either by watering too often, or by giving too much water at a time when the plant is too young to drink it all.

How often should I be watering my cannabis plants?

Water your marijuana when the top of the growing medium starts feeling dry up to your first knuckle. You should stick your finger 1-2″ into the soil. Wait if it’s damp, but water your plant once it feels dry.

  • Soil dries in 1 day or less? Give More Water at a Time (if that doesn’t work, you may need to transplant to a bigger pot)
  • Soil takes more than 3 days to dry? Give Less Water at a Time

An over watered cannabis plant will have leaves that are full of water, so the leaves will be firm to the touch and generally curling down (even from the stem of the leaf) almost as if it has too much water weight to hold the leaf out straight.

An under watered cannabis plant will have leaves that are brittle, limp, and lifeless. They will need to be watered every day just to keep them wet. The leaves will seem to be drooping but won’t appear as rounded and full as an over watered cannabis plant.

Leaves feel papery and thin on an underwatered plant, growing medium is dry

If it gets worse….

Now that you’ve (hopefully) got an idea about whether it’s over watering or underwatering, what’s the cure?

Or continue reading….

Over-Watering vs Under-Watering Remedies

Overwatering

Symptoms: seedling is droopy, growing medium is moist, damping off

Most common causes:

When a cannabis plant is “overwatered” it has less to do with the water and more to do with oxygen. Plants can even grow directly in water (hydroponics) but in order to thrive, roots need oxygen. In hydroponics, that’s accomplished by dissolving oxygen into the water. But when plants are grown in a container, too much water = not enough oxygen.

When a plant’s roots are sitting in water, they quickly use up all the oxygen until the growing medium starts to dry out. Without enough oxygen at the roots, the plant will start showing symptoms of oxygen deprivation. Luckily, there are many steps you can take to prevent overwatering your cannabis plants.

While overwatering can display many different symptoms, most overwatered cannabis plants look droopy, like this…

Despite what seems like an obvious cause, several different scenraios can end in overwatering. Here are some of the most common trouble-makers:

Big Pot, Small Seedling

When you have a small plant in a very big pot, it’s easy to overwater because the roots aren’t drinking much yet, and the big container takes a long time to dry out.

Notice how the plants in smaller containers have grown more than the plant that was put in a big container as a seedling. It’s common for plants in too-big containers to grow a little slowly at first.

  • (Recommended) Start seedlings in smaller container until they’re growing vigorously, then transfer to a larger container
  • If seedling is already in a big container, there’s still hope! When watering, give just a little water at a time in a small circle around the seedling. Then allow the top inch of your medium to mostly dry before watering again. Once the plant is growing vigorously, start watering as normal (with extra runoff water coming out the bottom every time)

These small cannabis plants (below) were put in big pots, and were given enough water to support a much larger plant. The plants couldn’t drink all the water that was given to them and as a result, their roots weren’t able to get the oxygen they needed and started “drowning.” Once the roots are out of commission, the leaves start drooping.

One way to prevent this from happening is to make sure your plants are in an appropriately sized container for each stage of their life; this is done with transplanting.

First, you need to get a general idea of the final container size which will be based on how big you want your plants to grow. The less often you transplant, the bigger the final size pot you’ll need because the roots will tend to grow out and cover the whole container if left too long. You can help avoid problems with roots getting rootbound by using a fabric pot (also known as a “Smart Pot”) or an air pot.

Final Container for Desired Plant Size – General guide
(the less often you transplant your plants, the bigger final size you’ll need)

2-3 gallon container

3-5 gallon container

5-7 gallon container

6-10 gallon container

8-10+ gallon container

But what size pot should you use for your seedlings?

For fastest growth rates, it’s better to plant young seedlings or clones in a very small container, like a disposable plastic solo cup.

For new seedlings and clones, use a small container if possible

Easy transplant guide – some popular transplant guideline:

  • Solo cup -> 1 gal -> 3 gal
  • Solo cup -> 1 gal -> 5 gal
  • Solo cup -> 2 gal -> 5 gal
  • Solo cup -> 1.5 gal -> 3 gal -> 5+ gal

There is no perfect transplant guide, but the one above should give you a general idea of where to start.

Why don’t you want to go from a solo cup to a 5 gallon pot? Or why not just start in a 5 gallon pot?

Young plants won’t be growing very fast yet, so they also won’t be using much water. When you completely saturate a big container that slow speed means that the plant won’t be able to drink all the water. Since so much of the water is contained in the middle without access to air, it won’t be able to dry out by evaporation. This means you’re left with a huge container full of wet potting mix.

The young cannabis plant roots will quickly use up all the available oxygen that’s been dissolved in the water, and then the roots will sit in water until the water slowly evaporates on its own. Some containers such as smart pots and air pots allow air in from the sides, which can help dry the growing medium faster, but it’s better to use proper technique from the beginning.

Planting in too big a container is sometimes called “overpotting.” It’s possible to get around this with special watering techniques (for example by giving plants just a little bit of water until they start “growing into” their containers) but starting plants in small containers and transplanting as needed can be a more straightforward way for some growers. Overpotting plants is also a waste of growing medium and nutrients, especially if the plants never get big enough to fully use their containers.

This OG Tahoe Kush seedling was overpotted, though this can be overcome by the grower just giving a little bit of water at a time until the plant starts growing vigorously. At that point, the grower can provide more and more water until they’re finally watering normally.

More information about container size and transplanting here: https://www.growweedeasy.com/germinate#what-size-pot

Small Pot, Big Seedling

While using a too-large container can cause problems for seedlings, so can too-small of a container.

Seedlings are happy in a small container like a solo cup for a while, but as they get bigger, their roots need more room. The roots tend to wrap around the outsides of the container, encasing the middle part so that water can’t get out. This is known as the plant being “root bound.”

If the seedling isn’t transferred to a bigger container in time, it can cause symptoms of overwatering, nutrient deficiencies, wilting, and sometimes very strange and unpredictable symptoms.

These plants were left in a too-small container for too long. Because they were drinking so fast, the grower watered them frequently – too frequently! This combination of being root bound and overwatering caused the plants to suffer.

A too small container, combined with overwatering – these conditions can cause some strange symptoms that often look like a nutrient deficiency

Pink leaves, red discoloration, rusty spots and edges… While it make look like these cannabis seedlings are experiencing nutrient deficiencies, all these symptoms are actually caused by a combination of overwatering plus a too-small pot.

When the roots aren’t happy, the plant isn’t able to uptake nutrients properly and cannabis seedlings can show a wide variety of strange problems.

It’s usually not a good sign when cannabis leaves start “crossing their fingers” like this (instead of having all the leaf tips spread out). While this can happen naturally every once in a while, you know for sure that you’re having a problem if the crossed fingers are combined with discoloration of the leaves. Also notice how the stems are bright red/pink.

The following cannabis plant was also overwatered and had no drainage. Notice how dark the soil is and the green algae growing all along the top of the soil – these are more signs the plant has been overwatered for quite a while. You should never water your plant when the soil on top is still wet, and if you notice lots of algae growing on top of your soil, it may be a sign that you’re overwatering on a regular basis. Leaving the top of the soil wet is also the number one reason growers get fungus gnats.

No Drainage (or poor drainage)

Cannabis roots need oxygen to thrive, and therefore they will have trouble if the roots are “drowned.” If water cannot run out the bottom of the container, it will pool at the roots, which causes overwatered plants.

  • Always start with a good growing medium that drains well – never use a clay based soil which holds onto way too much water. A high quality potting mix (especially mixed with some perlite) provides great drainage
  • Start with a smaller container to reduce the chances of overwatering seedlings
  • Make sure there are plenty of drainage holes to let water out the bottom of the container
  • If water runs through growing medium slowly, you can mix perlite into the potting mix to increase oxygen and quicken drainage
  • Water less often and less at a time until plant is drinking more
  • Get a container that helps the growing medium dry out from the sides (such as “Smart Pots” – highly recommended; or air pots).
  • Don’t allow plants to sit in a tray that has been collecting runoff water

This seedling started “damping off” (dying) due to terrible drainage from bad soil. Never use soil that looks like it contains clay!

Seedling is “damping off” due to bad soil with no drainage

Here’s another example of a seedling damping off due to too much water (drowning roots), whis time combined with not enough light. After a few days of these conditions, this seedling just fell over and started dying.

The following plant was grown in an unsuitable growing medium with no drainage and started showing signs of overwatering. Always start with a quality potting mix that has good drainage, and never allow the top of your growing medium to look this wet!

This “soil” is more like mud. The plant roots are drowning from lack of oxygen, causing severe wilting.

Watering too often

While oxygen is available to the roots immediately after watering, the roots use up all the oxygen quickly if they are sitting in water. If all the oxygen is gone, roots are not able to get what they need to help power growth, at least not until the growing medium begins to dry out and create new air spaces in the growing medium.

Keep roots happy for fast-growing plants

Each air spot in the potting mix provides roots with precious oxygen, but if there’s no air spots, roots start to “drown.” By watering seedlings less often, growers can ensure that roots are getting access to plenty of oxygen at all times.

Of course you should never allow roots to actually dry out – roots need moisture at all times. But for new growers who want to do everything possible for their new seedlings, it can seem like more water = better. Unfortunately, this isn’t true.

Roots work best when they get as much oxygen as possible while also staying completely moist at all times.

  • Wait until top inch is dry. Make sure that the top bit of potting mix has started to dry before you water seedlings again. Sometimes it can take a few days, depending on your growing medium, your environment and how much water you provided during the last watering.
  • Increase the number of air pockets in the growing medium by mixing in a “lighter” amendment like perlite to the potting mix. Perlite will allow the mix to hold onto more oxygen when mixed with heavy soil. Many cannabis soil growers will mix 30-40% perlite into their potting mix to make sure there’s lots of drainage and plenty of air available for the roots.
  • Provide air from the sides. Transplant to a container which allows air in from the sides like fabric pots (“Smart Pots” – highly recommended) or air pots.
  • Start in a smaller container until plant gets bigger so there’s less water in the potting mix that needs to dry. You’ll be able to water your plants more often while ensuring they get plenty of oxygen.
  • Water less when it’s cold. Plant processes tend to slow down when temps get cooler. This means that plants usually need water less often than normal after a cold snap.

This plant went through a few cool days but the grower continued to water as normal. As a result, the plants roots were surrounded by too much water and the plant started showing signs of overwatering.

The plant was watered the right amount each time, but too often. As a result, it shows some slight drooping. While this won’t kill the plant, the plant will definitely grow faster when the mix is allowed to dry out a bit so the roots are getting plenty of oxygen.

Underwatering – seedling is droopy, wilting, or not growing properly, and the growing medium around the seedling isn’t moist

While overwatering is the most common seedling symptom, underwatering is also a problem, especially for those who have been warned to avoid giving too much water.

It can be confusing because the symptoms often look similar to each other, which is why it’s important to learn good watering practices.

This seedling was underwatered – the grower had been warned many times to avoid overwatering, and went too far in the other direction. Notice that the growing medium looks bone dry.

It’s crucially important to make sure that plant roots have access to moisture at all times. Plants are constantly losing water through their leaves (called “transpiration”) and this is actually how plants get water up from the roots. As the plants lose water from the leaves, it pulls water up from the ground like a straw.

When there’s not enough water at the roots, many plant processes cease to function. If roots actually dry out, the dried shoots die.

Here’s another example of a young cannabis plant that is underwatered, even in a big container (where the problem is usually overwatering). Notice how this cannabis seedling is basically just wilting and falling over, while the potting mix looks completely dry.

Seedlings suffer greatly from being underwatered, even more so than from overwatering. Often the grower will actually be able to see how dry the growing medium is. A big sign that the plant is being under-watered is when you can see the soil separating from the container. In this case, you can see the starter cube separating from the soil because it’s so dry.

Underwatering is bad on it’s own, but it causes the most problems when young cannabis seedlings are also stressed by too high levels of nutrients, or when started in a “hot” (nutrient-enriched) soil.

When underwatering is combined with too much nutrients, seedlings often become dark green and stunted, with twisted and discolored new growth.

The solution for this (underwatering + high levels of nutrients) is simply to give the plants more water so they can establish roots and start growing again. Most plants will be able to grow out of this problem once they get enough water to start growing. While it’s not always the best idea to start out with a hot soil mix, most seedlings will easily grow into it if given a good growing environment.

This cannabis seedling is dark because it was underwatered in a “hot” soil mix, but after watering the plant as normal for a week or two, the plant started growing vigorously

Is a plant drooping because it got too much water, or not enough? Overwatered cannabis plants often have firm leaves, while the leaves of under-watered plants tend to be more limp and lifeless. Both can result in yellow leaves and other odd leaf symptoms. Learn how often you should be watering your marijuana plants!