The massive amount of water used in the agricultural industry and the lengths to which sustainable growers will go to conserve water would lead one to believe that dumping water on a cannabis plant wouldn’t be far off from what the plant actually needs. That’s not the case, though.

There isn’t a universal amount of water a cannabis plant requires. 

That quantity depends on the plant’s size, growth stage, growing medium, and atmosphere. A larger plant, higher temperature, and drier air are all conditions that require more water. If there is a lot of humidity, the plant needs less water. If it’s a smaller plant, you guessed it, it will need less water. Soil aeration is important too. No matter what, all plants need properly ventilated soil to facilitate the process of nutrient uptake; cannabis isn’t designed to grow in a swamp, nor is it made for a desert. Cannabis can grow in most climates, but the extreme ones are problematic, and that’s because of water.

Of course, a dehydrated plant is not a good thing. However, too little water is a much easier problem to solve than its opposite.

Another obvious sign of dehydration is a dusty soil medium. If the soil is always dry, it needs more water. Once water output is increased, these problems will likely resolve themselves.

Overwatered plants are a bit more complicated to treat. These plants will suffocate from a lack of oxygen, and this is a life-threatening problem. Oxygen is an essential part of nutrient absorption. Additionally, overwatered plants are at increased risk of mold and mildew, and these pathogens can be lethal. Since It is much harder to take water out of a growing medium than it is to put it in, growers should do their best to avoid overwatering, even if that risks dehydration.

Signs You're Overwatering a Plant

Drooping leaves: Did you know that, like humans, plants need oxygen to breathe? The reason soil aeration is so important is because those pockets of air make it possible for plants to consume oxygen. When plants are overwatered, the roots are suffocating in stagnant water, and that causes their leaves to droop. This drooping is usually the first sign of overwatered plants.

Leaves curving inward: Under-watered plants droop as well, but the difference between those leaves and the leaves of overwatered plants is that the latter’s will also curve inward. Overwatered plants’ leaves will feel firm but curve inward from the stem to the tip. If the tip of the leaf is the only part of it that is curving inward, it may be the sign of a nitrogen deficiency.

Yellowing leaves: Speaking of deficiencies, overwatered plants have them. Oxygen enables plants to metabolize nutrients, but overwatered plants have an oxygen problem. The roots are stuck in stagnant water and dense soil with no aeration. This deprives the plant of the oxygen it needs to uptake nutrients. Another reason for deficiency is that the nutrients get flushed out of the soil by the excess water.

Mold and mildew: One of the most dangerous threats to cannabis is mold. There are three types of mold that most frequently attack cannabis plants: bud rot, white powdery mildew, and fuzzy white mold. This fungus spreads easily and can ruin an entire harvest. It thrives in overly humid conditions. Overwatering creates a humid environment given the excess water in the soil and potentially even on the leaves depending on how much water is being dumped on the flower.

Slowed or stopped plant growth: Again, because of the lack of oxygen and nutrient uptake, overwatered plants will struggle to grow. In an overwatered plant, the roots are unable to function properly, and, in their weakened state, they become more susceptible to pathogens.

Pest infestations: Fungus gnats and root aphids love damp environments. These pests can stunt your plant’s growth, and, without any intervention, eat your plant until there is nothing left. If these harmful pests start showing up on your plants, it is a major red flag for overwatering.

Test Your Soil’s Water Levels

There are devices made to very accurately test the amount of water in the soil. A moisture meter is the best way to ensure that the soil is not dehydrated or saturated. Most of these devices are relatively inexpensive and don’t interfere with the plant’s root system the way that a finger check would.

If you don’t want to purchase a moisture meter, you can use your hands to measure the water. This is a bit more invasive and intuitive than the device, but it’s also pretty simple and completely free. Stick your fingers about an inch deep into the soil. If the soil is dry an inch below the surface, it needs more water. However, if the soil is saturated at that depth or beyond, stop watering your plant until the medium dries out a bit. The cannabis plant’s root system absorbs water about an inch below the surface and higher, so the extra water is wasted. Moreover, while thirsty, the cannabis plant can only drink so much. Any extra water is a step closer to an overwatered plant.

Test the water level either with a device or your fingers. Wait to water the plant until the soil is dry an inch deep. If you’re using a pot, water your plant until you get about 10-20% runoff; this ensures that you aren’t leaving any dry spots in your soil. If your plants take five days or longer to dry out, they may be overwatered or need better drainage. If they are dry in two days or less, they may be under-watered.