Marijuana Plant Watering Guide

Marijuana Plant Watering Guide

Autoflowering plants just like regular cannabis (Sativa and Indica) plants need water to grow and produce healthy leaves and buds. Water is the lifeblood of the plant and cannabis plants are about 80 % water and this liquid is used in almost all of the plants life processes starting from photosynthesis and transpiration to nutrient uptake and keeping the leafs stiff. So if water is so important what are the optimum amounts of water and when , how you need to water your plants?

First of all there are so many variables like temperature, humidity, growing medium, strain, climate conditions, pot size and so on that there is not a one method – fit all solution but there are general guidelines that can help you to water your plants properly.

But first before all the watering techniques and explanations you need to know what water to use. Basically any tap water will be fine but you should let it sit for at least 24 hours within an open top container as all the chlorine in the water will evaporate and the water will also heat up to the temperature of the growing room and you won’t damage your roots with cold water full of the toxic chlorine. Chlorine will evaporate in the form of bubbles on the container walls , so when those bubbles have gone away then you should also check the PH of that water and if everything is OK then you are good to go.

One growing myth is that reverse osmosis water will be better for your cannabis, but this is not the case as in the reverse osmosis process the water is stript from ALL of the nutrients so every micronutrient will need to be supplied artificially. Many grow nutrients will not have all of the micronutrients in adequate doses as they will expect some of them to be in the water , so be careful with that purified water!


Underwatering happens when the plants gets too little water and its leafs start wilting. This process is common in nature but not so common in indoor grow operations as growers usually do exactly the opposite from under watering. Marijuana plants need a little dry period for the potency and for the optimum growth but it should not get so extreme that the leafs start wilting. The wilting process happens because the water pressure inside the leafs is not high enough and the cells start shrinking so the overall structure of the leaf  bends under its own weight. You can fix underwatering by simply introducing water to the growing medium and you will be able to see how the leafs start slowly strengthening and that means that they can start to fully photosynthesise again.

Underweatered Marijuana Plant

Buy LED Grow Lights today

These are trusted partners to delivery Best LED Grow Lights worldwide.


Over Watering marijuana plants is one of the most common inexperienced growers mistakes as usually they want to supply plenty of water but they don’t realize that too much water slows down the growth and excessive amount of water can introduce some mold or fungus that can severely damaging the plant. First signs of overwatering are that the leafs start to curl and bend strangely and the leaf tips start to turn yellow. This process is often misdiagnosed for nutrient deficiency but can be easily spotted if you know what to look for. Overwatering can’t be cured immediately but letting the plant use up all the water in the growing medium will be a start and slowly your weed plants will recover and keep on growing.

Optimum watering

If your automatic or regular plants get optimum water starting from the seedling all through the flowering phase then they will grow fast and will give you huge harvest. In different plants life cycles there are different techniques of watering and different amounts of water you need to supply.


In the seedling phase you need to supply your plants with plenty of water but not in share volume but in frequency. You need to keep your growing medium wet for the new seedling to grow and develop properly so you need to water your soil at least twice a day but with a minimum amount of water as too much water can kill the little sprout! My suggestion is to use a hand sprayer and spray the water around the newly developed plant but not directly on the stem as it is still fragile and can bend over. As for the amount I suggest to simply wet the surface as the rest of the pot will be wet from the pre soaking process before planting the seed in the ground. This moisture in the ground will be enough for the seedling to produce a good root ball so be careful with watering at this stage! Autoflowering seedlings are a little tougher than regular cannabis ones but there are no differences between autoflower and other cannabis plants in the watering process for this phase.


At the vegetative growth stage autoflowers will also need the same care as regular cannabis plants and that means that the watering process needs to be repeated every day if your pot is small or every other day if the pot is medium to large. Basically depending on the growing conditions every grower will need different time periods between waterings but a good rule is to check the first centimeters of the soil and if it is dry then it is time to water! There are also soil humidity meters but in general cannabis growers will water their plants depending on the surface moisture or holding the pot up / setting it on the site, to feel the weight of the soil, and with time every grower will be able to tell that the weight is too low so it is time to water your herb!


At the flowering phase you need to continue as in the vegetative growth phase because autoflwoers can grow under 24 hours of light and still flower! This skill gives them advantages but in the watering department it gives a bit more work as the flowers will chew up more water but the air temperature will also increase the water evaporation so you will need to water more frequently than you would regular weed plants. But again do the watering only when the soil is moist at the top or the pot is too light when picked up!

After knowing the right method for each phase you need to know exactly how to water your plants. In the seedling phase as I mentioned before you need to get a hand sprayer because large quantities of water can kill the little plant. But when the seedling phase is over you most definitely need large amounts of water to sustain optimum growth. This means that at each of the flowering and vegetative phases you need to pour as much water in the growing medium to get a 10% to 30% runoff water at the bottom as only then the growing medium will be completely wet and you won’t need to worry about dry soil pockets or dry spots full of nutrient that can give overdose to your marijuana plant.

If however the soil gets too dry between watering phases then you can get runoff exactly as you start watering because the soil can be pulled away from the pot sides and water will flow down by the sides directly through the pot. If this is the case then you have three options:

  • You can slowly wet the soil adding a little water in multiple watering cycles. You will need to do this process till the soil expands again. This process can be long as you will need multiple waterings in a short period of time so if you choose to do this be patient and don’t rush the process because you need the whole soil to get moist.

  • You can also crumple the top soil a bit in the gaps between the pot walls but be careful not to damage any roots. You can also add additional growing medium at those sides, but give exactly the same medium as the one you used for the initial potting.

  • The third and final chance is to mix a little bio-degradable soap inside the water as the soap will make the water “wetter” and it will more easily wet the growing medium and soak in the dried up parts so there won’t be as much runoff as without the soap.  If you choose this method know that only bio-degradable sop will be OK as other soaps contain hazardous chemicals. if you add soap to your water be sure to measure the PH of the water as some soaps can increase the PH level!

So now you know almost all there is about the watering process on cannabis plants but if I missed something or you have some additional question come to my blog and look around or ask for answers on any topic related to autoflowering or regular marijuana plants!

GD Star Rating
Marijuana Plant Watering Guide, 8.0 out of 10 based on 68 ratings

7 thoughts on “Marijuana Plant Watering Guide

  1. Bud man says:

    I am using coco in my pots on wk 2 and no nutes added yet just water and it’s turning green in the btm of my tent any help with what this could b wid b appreciated

    GD Star Rating
  2. Antonio says:

    Everything is well explained except one. How much water is needed when watering plants? Half litre, litre or just water untill it starts to pour from bottom of the pot?

    GD Star Rating
  3. Nate Jones says:

    I am using a drip irrigation that allows me to water the plant well then I can turn it off to let it dry out a bit then ad can turn it back on. However I am worried that I am not soaking the plant fast enough to get the 10-30% run off, ensuring that dry pockets are soaked. I am wondering if this is an issue for automated irrigation systems?

    Does any one have the water requirements (or a rough idea) for plants that are propagating indoors? Also how much less water does a plant that is in vegetative growth use compared to a flowering plant? Any ideas or suggestions would be great!


    GD Star Rating
  4. Steve says:

    Hello, it is the first time I attempt to grow and me and my buddy have a debate as to how frequent should I water my baby plants. Specifically, I have an ebb & flow system adjusted to water my plants 3 times evenly (every 8 hours) during light hours. My buddy though, insists that I should allow water flow into my tray every 30 minutes with a 15 min of no water interval in order to prevent clay pellets dry completely as this will cause a change in ph levels.
    How should I proceed whit it?

    GD Star Rating
    • Jake says:

      Timing for a hydroponic Ebb and Flow system
      Each individual flood should last around a half hour. Allow the flood tray to fill for 15 minutes and then to drain for 15 minutes. This is ideal for modern analog timers which are normally separated into 15 minute segments. Simply depress two segments at each time when you want a flood to occur.

      As with all areas of hydroponics, your timing will depend on the details of your set up. What you require is that your roots get plenty of oxygen between flows, but are not allowed to dry out too much so that it begins to adversely affect the plants.

      How many times per day to flood your plants is open to debate. We have seen suggested timings given from one to six times per day. The following suggestions should help you to establish your own system depending on climate.

      Twice per day – in cooler, more humid environments or if using a slow draining medium such as Rockwool;
      Three times per day – in warmer environments or if using a fast draining medium such as expanded clay pellets;
      Four times per day – in very warm, dry, or outdoor environments with fast draining growing medium.
      There will also be a difference between how many times per day you flood flowering or vegetative plants. During the veg period you will want to flood one more time per day than during the flowering period. This is to match the extra 6 hours of lighting that you are giving the plants during this time.

      Whether you are vegging or flowering, you should allow your plants to ‘sleep’ and refrain from flooding during their night period. So if, for example, you have your plants vegging at 18 hours per day and want to flood three times per day, you will not be flooding the plants every 8 hours (00:00/8:00/16:00) but evenly across the plants’ day period (00:00/6:00/12:00). This allows for the plant to rest during the lights out period from 18:00 to 00:00.

      GD Star Rating
  5. Kori Township says:

    Hello, I show no signs of under watering, but my girls are bone dry at the bottom of their pots! They have roots at the bottom, they are growing quickly and very healthy, but I still feel like they need more water. Any advice?

    GD Star Rating

Leave a Reply

Your email address will not be published. Required fields are marked *


Time limit is exhausted. Please reload CAPTCHA.