How much water do weed plants need daily?

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Growing cannabis can be an exciting and rewarding experience, but it’s not without its challenges. One of the most common mistakes that beginner growers make is overwatering their plants. But fear not, we’re here to help you navigate the murky waters of cannabis watering.

How many Litres of water does a weed plant need?

When it comes to how much water to give to your cannabis plants, there’s no one size fits all answer. The amount of water you give your plants really depends on the size of your plants, the growing medium, and the environmental conditions. If you are growing outdoors in a hot country, you will need to water them more often, but if the conditions are rainy then you will need to water them less. Equally if you are growing hydroponically then the plants are normally watered on a timed system that ciculates water continuously. Whereas those that are growing in soil will need to water once or twice a day.

When growing indoors, a good rule of thumb is to water your plants when the top inch of soil feels dry to the touch. As for the amount of water, a general guideline is to provide around 2-3 liters of water per plant, but as we have said this can vary based on the factors mentioned above.

Can I just use tap water for my weed plant?

Yes, you can use tap water for your cannabis plants, however it’s important to first test the quality of your tap water and amend it accordingly. If your tap water is high in minerals or chlorine, it can have a negative impact on your plants. You can use a water filter or let your tap water sit out for 24-48 hours before using it to water your plants. Alternatively, you can use bottled or distilled water, but this can be costly and not the most sustainable option. You should also measure the pH of any water before you give it to your plants. All cannabis plants need water that falls between a pH of 6.0 – 7.0. Get yourself a pH meter from amazon or your local grow shop, this will become an invaluable tool for any future grows.

How can you tell when weed plants need water?

The answer is simple, you water them when the soil feels dry up to around 1 inch. The most straight foward way of testing this is….

  • Wait until the growing medium feels dry in roughly the first inch of soil.
  • Water the plant until you begin to see some water running out the bottom, allow only a little to run out the bottom of the pot.
  • Clean up any run off water.
  • If the water takes a long time to come through then you either have not poured enough water or you could have a draining issue (see below).

How to water marijuana seedlings

person watering cannabis seedling in soil with hand

​It is just as important to properly water your seedlings, remember seedlings are very delicate so too much or too little water can easily kill them. Seeds don’t have any roots so let them dry out and it can kill them, equally over watering can drown them. Ideally you should keep them moist but not wet, you can do this by spraying them with a mist instead of pouring water over them, this prevents the risk of over watering. ​

As the plant grows you can begin to water it, make sure you keep an eye out for any signs of mold as this can easily kill a plant and is common in the hot humid environments that are created in a grow room. If your soil is wet and you are worried that you have over watered then allow the soil to dry out for a few days, this will allow the plant to absorb all the water it can and any excess water to drain off preventing the risk of mold developing.

How to improve drainage for cannabis plants

how to water marijuana plants correctly

It is very important to have good drainage as this is one of the major causes of mold and bacteria build up and if a plant becomes waterlogged it can cause damage to its structure which will then begin to droop.

To improve drainage follow these simple rules:

  • Make sure your pot has holes in the bottom for drainage or use a fabric pot (image below) these are made with a breathable cloth like material that allow the water to come out of any part of the pot and also assist with getting oxygen to the roots. 
  • Add perlite into your growing medium, this creates tiny air pockets in the soil and keeps it loose allowing water to drain more effectively.
  • DO NOT use wood chips or bark, they are notoriously bad for growing marijuana and can retain water allowing mold and bacteria to build up.
  • Make sure you water the plants slowly and evenly, by this I mean do not pour the water fast in one corner of the pot, pour it evenly around the entire surface of each pot. If you pour the water in just one part of the pot it can create channels through the soil which then allows the water to drain through the pot too fast not actually giving the plants roots enough time to absorb the water it needs.
  • Water in the morning – Ideally you should water the plants in the morning if outside or when the lights have just turned on if inside. This means the plant has an entire day of sunlight ahead of it and plenty of water on board to help it carry out the process of photosynthesis. Watering in the morning also reduces the chances of mold building up.
  • Use a larger pot (once the plant is big enough to be repotted) – If you use a larger pot than needed not only will it give the plant ample room for growth, but it also will save you lots of time as the plant gets bigger. This is because larger pots can retain more water and therefore you can afford to water the plants less frequently.

Growing with compost​

​When growing with compost or any amended soil such as super soil you will not need to add nutrients into the water because they will be provided automatically by the soil. Make sure when you are watering and using this soil that you do not allow too much run off as this will cause the nutrients in the soil to drain out of the pot and go to waste. If you are adding the nutrients into the water manually then don’t worry about a little run off, this will actually assist in preventing nutrient build up in the soil.

Signs of over or under watering​

​To prevent over or under watering make sure you are getting around 10-20% run off each time you water and make sure your plants are watered evenly, if you wat er lots in just one corner of the pot the water can easily drain through without the plant absorbing enough eventually causing under watering.

What do under watered weed plants look like?

  • Plant and leaves become droopy and limp (see image on right).
  • Leaves are dry and crispy and not as rounded.
  • Leaves feel dry and thin.
  • Soil is very dry to the touch
over watered weed plant

What do over watered weed plants look like?

  • Plant begins to droop and leaves begin to curl downwards.
  • Leaves feel firm and are well rounded
  • Leaves can begin to turn yellow
  • Soil is still damp to the touch

Is overwatering better than underwatering weed?

The short answer is no. Overwatering your plants can be just as harmful, if not more so, than underwatering them. When you overwater your plants, the roots can become waterlogged, which can lead to root rot and a whole host of other issues. This can stunt the growth of your plants and even kill them in severe cases. Underwatering your plants can also cause stress and hinder growth, but it’s much easier to recover from than overwatering.

How long do overwatered plants take to recover?

Recovering overwatered plants can take time and patience. Follow these 3 simple steps to allow your overwatered cannabis plant to recover….

  • The first step is to stop watering your plants and allow the soil to dry out.
  • You can also gently remove any excess water from the soil using a turkey baster or similar tool.
  • Once the soil has dried out, you can resume watering your plants, but be sure to water them less frequently and in smaller amounts. It can take a few weeks for your plants to recover fully, but with the right care and attention, they should bounce back.

Watering your plants correctly is vital to their health, equally important is providing the right nutrients to allow them to thrive, have a read of our comprehensive guide to nutrients or how pH effects cannabis plants.

In conclusion, watering your cannabis plants is a tricky balancing act. But by paying attention to your plants’ and being mindful of your watering habits, you will ensure that your plants are not over or under watered.

Remember, just like people, every plant is different, so it’s important to adjust your watering routine to suit the size, breed and climate conditions for the grow. If in doubt, refer back to the paragraph above on ‘how can you tell when to water weed plants’. And if you are still unsure when to water them, it is easier to recover from under watering than over watering so giving it one extra day to allow the soil to dry out a little more before watering again won’t do too much harm.

Joe Musgrave

Joe Musgrave is a keen 420 blogger who writes about all things cannabis. After harnessing his green thumbed skills through years of working on cannabis farms, Joe now shares his knowledge with the rest of the online 420 community.

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