How to Prevent Underwatering and Overwatering Cannabis Plants?

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Added 14 January 2023

When you are growing cannabis plants, you need to take care of so many things — grow lights, temperature, relative humidity, growing medium, nutrients, fertilizers, supplements, beneficial bacteria, etc.

In this maze of various things, many growers often overlook perhaps the most important aspect of growing a healthy cannabis plant: water. 

Either due to human error or lack of understanding, many growers don’t water their cannabis plants properly, often underwatering or overwatering the plants. Both of these scenarios are dangerous. 

Underwatering can cause drought-like problems for your plant and too much water can drown your cannabis plant. To avoid such problems, keep reading to know all about underwatering and overwatering cannabis plants.

Overwatering Cannabis Plants

overwatering cannabis plants

Image Credit - Lazuli 

Overwatering cannabis plants is when you give your plant more water than necessary or required. This is one of the most common mistakes new growers make when growing cannabis — thinking more water will result in a healthier plant. But the reality is often different.

Giving your plant a lot of water or overwatering it can have drastic consequences on your plant’s health, growth, and yield.

But human error isn’t the only reason your cannabis plant may experience overwatering; it can also occur due to the following reasons:

  • If the medium has poor drainage, it will hold more water instead of letting excess of it drain off
  • If the container is too large, it may end up holding more water than your plant requires
  • If you water the plant before turning the lights off or during the dark hours — the plant cannot intake water during this time and excess water cannot evaporate 

What Happens If You Overwater Cannabis Plants?

What Happens If You Overwater Cannabis Plants?

Image Credit - Arcadios

Overwatering is bad, but how bad? What exactly happens if you overwater your cannabis plant? Here are some of the ways your plant can get damaged by overwatering:

  • Leaves start drooping due to excess moisture content within; they may also become firm and thick
  • The leaves may also start losing their color and turning yellow, which is due to a nutrient problem — a side effect of overwatering
  • The plant’s growth will drastically slow down, and in severe cases, it can even stop growing entirely — this is due to anaerobic conditions due to oxygen deprivation in the root zone
  • The plant may also experience pest problems as its resistance to pests weakens
  • Overwatering can also lead to fungal or bacterial growth, especially in the root zone, leading to serious conditions like root rot; in severe cases, the root system may get completely destroyed 
  • Eventually, the plant may die 

How to Fix an Overwatered Cannabis Plant?

How to Fix an Overwatered Cannabis Plant?

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Overwatering cannabis plant isn’t a major concern as long as you fix the problem immediately. Considering how common this is, most new growers would end up with a dead plant if the problem wasn’t so forgiving. 

Follow these tips to fix an overwatered cannabis plant.

1. First, Check the Extent of the Damage

Your first step should be to assess the damage to your plant — if there is mold growth, fungus gnats, drooping leaves, or if the plant looks too weak — you are better off tossing the plant and starting anew. It’s not worth it at this point.

On the other hand, if your plant is somewhat healthy but with moderate symptoms of overwatering, you can save it. 

2. Let Your Plant Dry Out

The next step is to allow your plant to dry out. Yes, you may pity your plant’s appearance at this point and want to water it, but don’t. Avoid watering the plant until the growing medium is properly dried. 

Overwatering causes various difficulties for your plant, including nutrient problems, pH imbalance, and a lot more. Your plant will take some time to recover, so you need to be patient.

3. Now, Lightly Water the Plant

Once the substrate is dry, you can resume watering your cannabis plant again. If you are growing cannabis in soil, water until you see some water runoff. And if you are using a soilless medium, keep your pH meter ready.

Adjust the pH of the water and the growing medium before watering. If the pH is off, use a pH down/up solution to rebalance the pH. Otherwise, you may throw off the nutrient balance in the medium.

4. Observe the Plant

Lastly, you need to observe the plant and see if it recovers. Remember that it can take a few days for your plant to show progress, so you must be patient. Look for signs of progress like the leaves no longer wilting or curling, fungus gnats going away, the plant looking more vigorous and healthy, etc.

How to Avoid Overwatering Cannabis Plants?

How to Avoid Overwatering Cannabis Plants?

Fixing an overwatered cannabis plant is easy, but preventing the entire scenario is even easier. Follow these tips to avoid overwatering the cannabis plant.

1. Finetune the Environmental Conditions 

The first step is to ensure the environmental conditions are healthy for your cannabis plant. In an indoor grow room, the environment should be:

  • Temperature ranging from 75°F to 85°F (24°C to 29°C)
  • Relative humidity between 25% to 45%
  • Adequate airflow and a constant supply of fresh air

On the other hand, for outdoor cannabis plants, it should be:

  • The plant must be located in a sunny area with enough light and air exposure
  • Only germinate seeds after spring showers (may differ on your specific location and climate)

2. Determine the Perfect Irrigation Interval

Next, you want to decide on specific periods when you water your cannabis plants. The time should factor in the light cycle and climate so that you can strike a balance that keeps the growing medium from being too wet or dry. 

Doing so is easy. Follow these steps:

  • Water your cannabis plant and wait until the medium is half dry 
  • Your plant will begin to wilt slightly 
  • Record the time when you water the plant and when it starts wilting 

For example, if you water your plant on Monday and it starts wilting on Wednesday, your plant can go without water for two whole days before starting to wilt. Depending on your local climate, the interval can range from one to three days.

Do note that this interval will shorten as your plant grows.

3. Change Your Grow Medium

If your growing medium is too dense or holds a lot of water, no matter what you do, your plant will experience overwatering problems. This is because the medium never dries completely and starts drowning the roots. 

In that case, you can add other materials to your growing medium, such as:

  • Perlite 
  • Coco coir
  • Clay pebbles
  • Peat moss
  • Sand

These materials improve aeration in the substrate, which prevents the roots from constantly being drowned in water. Start with 15% to 20% of such materials in your soil first and take it from there. 

4. Check the Pots

You may have the best soil in town, but if your pots lack any drainage holes, the roots can still drown. So, you need to also check the pots, specifically the drain holes. Ensure they are present and not clogged. 

If the drain holes are good, ensure the runoff water does not collect under the pot — the soil can sometimes reabsorb the water. 

Underwatering Cannabis Plants

Underwatering Cannabis Plants

Underwatering is when you fail to give your cannabis plant enough water — and unlike overwatering, this problem is not so common. Generally, growers lean towards giving their cannabis plants more water than less.

However, this can still happen to you. Here are some of the reasons why your plant may be underwatered:

  • You are too conservative with your watering routine
  • Or you are lazy and procrastinate on watering your plant
  • The growing environment is too dry, hot, or windy
  • The growing medium drains too fast 
  • The container is too small for your plant and cannot hold enough water

What Happens If You Underwater Cannabis Plants?

What Happens If You Underwater Cannabis Plants?

Like overwatering, underwatering is also bad for your plant — it can make your plant stop growing and eventually kill it. Here is how underwatering can damage your cannabis plant:

  • Your plant will look weak and start wilting since it is starved of water
  • The leaves will begin to wilt and turn fragile or crunchy due to lack of moisture content within 
  • The growing medium will be super dry 
  • Due to a dry medium, the root system may also dry up, causing a stunted growth 
  • The medium may also experience pH fluctuations or salt buildup, which can lead to symptoms of nutrient lockout or deficiency
  • Eventually, your plant can even die due to lack of water

How to Fix an Underwatered Cannabis Plant?

How to Fix an Underwatered Cannabis Plant?

If your cannabis plant seems underwatered, you can easily fix it. But the trick is not as simple as flooding the pot with water. Instead, follow these tips to fix an underwatered cannabis plant.

1. Check the Extent of Damage

Your first step should be to check your plant to see if it can still be saved. As long as the leaves are not losing their green color or turning brown, your plant can be recovered. Brown leaves are a sign of a dying plant.

If a lot of the leaves have turned brown, it is better to just toss the plant instead of trying to revive it. 

2. Water the Base of the Plant

If the plant is recoverable, you should immediately water the plant to offset the deficiency. However, you don’t want to suddenly add a lot of water — it can shock your plant. The goal is to revive your plant slowly, not shock it.

Instead, only water 250 to 500 ml of water, depending on your plant’s size. If you are growing hydroponic cannabis, you should check the water’s pH balance and add ¼ of the standard nutrient content to it before watering. 

3. Continue Watering Your Plant

Once you have slowly introduced more water to your plant, you need to revamp your watering routine so the same problem does not occur again. Remember, water your plant in the early morning. 

And don’t let the soil dry out. If the top inch of the soil is dry, water the plant to maintain the moisture levels in the soil.

4. Keep an Eye on Your Plant

Depending on how severe the water deficiency was, your plant can come back to life in half an hour or an entire day. However, if your plant shows no sign of progress after 24 hours, it is likely dead and you should toss it. 

How to Avoid Underwatering Cannabis Plants?

How to Avoid Underwatering Cannabis Plants?

Image Credit - vutra

Fortunately, preventing underwatering is a lot easier. To ensure your plant does not face underwatering again in the future, follow these steps.

1. Figure Out How Fast Your Plant Absorbs Water

Water your plant and see how long it takes for the top inch of the soil to dry or for the container to feel lighter. If it is abnormally fast, like a few hours, you need to check the pot size and environmental conditions for the plant.

Additionally, ensure you give your plant enough water. Ideally, you should water your plant until some of it comes out from the drainage as runoff. 

2. Check the Pot Size and the Growing Environment

If the water dries up too quickly, check the environment of your grow room or the garden. Water can dry out quickly if the weather is too hot or dry or if the winds are too strong. On the other hand, a smaller pot size means less water available for the root system, so you want to ensure your pot is adequate for your plant, too.

Sometimes, the pot may be too small for your plant. In that case, you should increase the pot size so that the medium can retain more water within, preventing underwatering. We recommend using pots over 3 to 5 gallons.

3. Improve Your Grow Medium’s Water Retention

Ideally, when you water the plant, around 20% of the water should run off from the drain holes. But if more water gets drained, you need to improve your growing medium’s water retention so it can hold more water. 

You can add materials to your growing medium to improve its water retention capacity. You can choose one of the following materials:

  • Coco coir
  • Peat moss
  • Vermiculite

Add 10% to 20% of one of these materials to your growing medium to ensure the water does not drain out of the soil too quickly. Alternatively, you can also use a mulch to cover the soil from the top and prevent water from evaporating too quickly.

Other Factors to Prevent Overwatering and Underwatering Cannabis Plants

There are a few factors that often get overlooked but can help prevent overwatering or underwatering your cannabis plant, such as the following.

1. Watering Schedule 

With many factors coming into play, setting the right watering schedule for your cannabis plant can get tricky sometimes. But this is an essential skill to learn if you want to grow healthy cannabis plants. 

And as you gain more experience in growing cannabis, you will be able to learn how to set the schedule more efficiently and quickly — all by simply assessing your plant’s growth. But until you reach there, you need to start at a baseline, which is as follows.

  • Watering a Cannabis Seedling

For cannabis seedlings, you don’t need to water them as much. In fact, in some cases, you don’t even have to bother about watering at all because seedlings have very low transpiration rates. 

The problem often occurs if you overwater seedlings, which can cause stunted growth in the plants. The seedlings can also experience stress if the water flow is too much.

  • Watering a Vegetative Cannabis Plant

On the other hand, your cannabis plant will require a lot more water when it is growing during the vegetative stage. During this stage, plants produce leaves that increase their transpiration rates significantly. At the same time, the root system also expands and absorbs more water.

You need to water your plant once every couple of days, depending on various factors as mentioned above. Learn to read your plant and feed it water accordingly.

During the early vegetative stage, when the plant is still small, you should give less water more frequently — this encourages root growth, which is good for the plant’s yield. As the plant grows, you can move to feed it more water less frequently.

  • Watering a Blooming Cannabis Plant

During the flowering stage, watering your plant becomes even more crucial and your plant will need more water. Again, listen to your plant and feed it water accordingly. But at all costs, avoid overwatering your cannabis plant at this stage as it can cause the buds to experience burns.

2. Water Until There is Runoff

When watering your cannabis plant, it can be hard to know how much water you need to feed your plant — are 2 gallons enough, or do you need three? Unfortunately, there is no fixed answer. It all depends on your plant’s genetics, medium, temperature, humidity, etc.

However, there is an easy way to get it right — think of it like a hack. As soon as the top inch of the soil gets dry, you should water your plant until you see 15% to 20% of the water running off from the drain holes. 

The runoff water is a sign that you have adequately watered the substrate enough for the plant to absorb. 

Protip: you should also check the pH of the runoff water as it is an accurate indication of the substrate’s pH. If the pH is different from that of your water and nutrient solution, you need to flush your plants — there is likely salt buildup in the root zone.

3. Only Water During the Day

You should also avoid watering your plant when it's night or after turning off the grow lights. This is because plants expend a lot of their energy during the day, which requires more water, and the cooler temperatures of the night can increase the chances of infestations. 

So, you should only water the plant early in the morning or one hour after turning on the grow lights. 

4. Use Drip Irrigation

Take all of your headaches away by installing a drip irrigation system in your cannabis garden. It is easy to set up. You can either use plastic bottles or pipes with holes drilled into them, which will provide a consistent supply of water to your plant.

On the other hand, if you don’t mind splurging a little, you should get yourself automatic watering stakes — they are easy and risk-free. 

Stick the stake in the pot and the wick in the water reservoir, which will pull water from the reservoir by reverse osmosis whenever the growing medium starts drying out.

Summary: How to Prevent Underwatering and Overwatering Cannabis Plants?

Watering is easy to get right and even easier to get wrong if you are not careful. You can either dry or drown your cannabis plant, which can have severe consequences on its health and eventual yield. This is why you must always pay close attention to your cannabis plant. 

To sum up, here are the points you should always keep in mind to perfect the watering routine for your plant:

  • When the top inch of the soil gets dry, water your plant
  • Avoid watering your plant during the dark hours or night
  • Look for signs of overwatering or underwatering, and if you see any signs, act immediately
  • Ensure the growing environment is ideal — the wrong environment can lead to faster evaporation of water or improper transpiration rates in the plant
  • Make sure the growing medium has adequate air and water retention — it is recommended to mix special materials like perlite, coco coir, vermiculite, etc. into your soil 
  • Use the right pot size to not only prevent incorrect watering but also root lock
  • Always look for runoff water when growing in a container — ideally, 10% to 20% of the water should runoff when you are watering 

Follow the guidelines and tips mentioned above and you will be able to perfect your plant’s watering routine. 


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