November 16, 2017

Ultimate Guide to Watering Cannabis the Right Way

Watering your plant is undeniably a crucial part of the growing process. You care for your plant like you would care your baby. When you want to nurture it perfectly, everything you provide it should be perfect, even the amount of water! Smart grow tents presents the ultimate guide to everything you need to know to water your cannabis the right way.

How much water does cannabis plant need?

When you water your cannabis make sure you have some runoff water after your pot is thoroughly soaked. Water at least quarter the volume of the planter. For example, if your planter is 1L, pour about 0.25 L of water in each irrigation.

Avoid keeping your roots saturated with proper drainage. Poke holes in the bottom of the pot else your plant may get waterlogged or overwatered. Some people put rocks or gravel in the bottom of the pot to aid drainage.

When should I water cannabis plant?

Cannabis does not like continuous irrigation!  

Overwatering can damage the root system and rot the pant. It is important to water them thoroughly and then wait until its substrate dries completely. The drying process is essential for preserving the crop.  Thus, you only need to water it every 3 -5 days. However, if you are growing it in a small planter at a later stage, you will have to water it more often.

What is the best water for cannabis plant?

Marijuana grows optimally with temperatures around 22 degree Celsius (room temperature) a pH of about 6.5. At this pH, the plant can easily absorb all the nutrients present in the soil.

Sometimes, the plant suffers from ‘nutrients lockout.' This is not due to excessive or deficiency of nutrients. This is mostly caused by the pH of water. Highly acidic water will restrict the plant from taking up the calcium and magnesium present in the soil, while highly alkaline water will hamper iron absorption.  

What is the correct nutrients formula for cannabis plant?

Firstly, it is important to note that providing nutrient water to cannabis plant every day will lead to salt deposition over the soil surface. Therefore, make sure to do it alternatively. The plain water will clean salt deposits, if any.

The most important nutrients in the life of cannabis plant are Nitrogen, Phosphorus, and Potassium, sometimes abbreviated as N-P-K. Bottled nutrients have different proportions of these. The bottles list chemical ratios as three numbers. For example 20 – 5 – 5 contain five times more nitrogen than phosphorus and potassium. 0 - 0 - 10 contains only potassium.

Different stages of the cannabis plant demand these nutrients in various proportions.

Vegetative Stage:

N (High) – P (Medium) – K (High)

Purchase the bottle that has a high amount of nitrogen. Nitrogen supply is of uttermost importance during the initial vegetative stage of the plant. Thus, bottles with numbers 9-3-6 and 3-2-4 prove to the best for this stage. A 5-5-5 numbered bottle also works well, as it has a generic even NPK ratio.

Transition Stage:

The best nutrient ratio for this stage is 5-5-5. To prepare for the flowering stage, the plant needs nitrogen to develop more leaves and stem.

Flowering Stage:

N (Low) – P (Medium) – K (High)

The plant needs to shift focus from growing more stems and leaves to growing more buds. Therefore, it is important to cut down on the nitrogen supply. Buds demand phosphorus and potassium supply for their growth. The best nutrients ratios for this stage are 5-15-14, 2-7-7 and 2-3-5.

Are liquid fertilizers good for cannabis plant?

We advise using liquid fertilizers minimally. The roots of marijuana plant absorb liquid fertilizers very swiftly. No, this is not a good thing because it leads to the misconception that the plant needs more nutrients. Thus, we intend to pour more liquid fertilizer to the plant. Ultimately, harming the plant.

Therefore, in case there arises a need to apply liquid fertilizer to the plant; make sure to mix the fertilizer in water at the source. The fertilizer should well-diluted and applied in appropriate proportions. When you have an option to choose from chemical and biological liquid fertilizers, without a second thought, go for the biological one. They are safer for the plant and non-toxic for your health.

How to know if it’s over-watered or under-watered?

Over Watered Plant


  • Plant starts dropping immediately after watering
  • Leave are firm yet completely curled


Don’t keep watering it as you regularly do.

Dig your finger into the soil check if the soil is dry up to the first knuckle. If the medium is dry then water it until you see 30% runoff water drained

Underwatered Plant


  • Plant starts wilting
  • Leave become dry, lifeless and crispy


Water in large quantity and more often.

It is possible that the plant has outgrown the space. If this is the case, transfer it to a larger planter that can hold more water.

Products to keep your cannabis plant well hydrated

Drip line

Most efficient way of watering plants is through drip line. It ensures that the plant gets water consistently and in appropriate quantity. It prevents waterlogging as it doesn’t let water stay on the surface. It helps distribute the water evenly across the planter.


A product of heated obsidian, perlite, is mixed with soil to loosen it. Perlite is an organic lightweight soil conditioner. It prevents caking while improving soil drainage and aeration. This also helps promote good oxygen flow.

Super soil

Soil mixed with wood chips harms cannabis. Growing your marijuana in composted super soil is important. Organic super soil contains forest humus, sandy loam, and sphagnum peat moss. It is very healthy for cannabis plant.

Smart pots

Smart pots are weightless, flexible, reusable and eco-friendly fabric containers. They provide better oxygen flow, better drainage, and a better cooling system; It's a three-in-one solution for better cannabis growth.

Cannabis Watering Guide Conclusion

From this basic guide, novice growers may get a fair good idea about watering their cannabis. However, it is only a guide. Modifications to the basic principles can be made according to the choice of strain, type of medium, local climate and various other factors. We always encourage experimentation.


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