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Answered: How to Water Cannabis Plants – Tips and Expert Advice


“Answered” is a blog series from THC University that answers the internet’s most sought-after questions related to cannabis. We cover everything from cultivation to making edibles to smoking to finding a job in cannabis. 


Today, we’re talking about water. Specifically, how to properly water your cannabis plants, which is NOT the same as watering a traditional houseplant. This post covers the need-to-know information you need to turn cannabis seeds into plants in the flowering stage and eventually the harvesting stage. 



How much water do weed plants need? 

The most common cannabis watering mistake is overwatering. Instead, cycle your watering between wet and dry periods – don’t constantly water your cannabis!


On the other hand, it’s still possible to underwater marijuana plants. Find the right balance so your plants get enough water. 


The amount of water your cannabis will need is largely dependent on the growing medium (aka substrate or potting soil) you use. The more compact your soil type is, the less water it will need.  


Typically, you’ll want to soak the marijuana plant with 25% of the pot’s capacity so the plant’s root system can absorb the water. 


Here’s a breakdown of a general weed plant watering schedule: 


Germination: Water every 4-7 days


Seedling: Water every 3-7 days


Vegetative: Water every 2-4 days


Flowering: Water every 2-3 days



How frequently should you water cannabis? 

The rule of thumb for growing cannabis is to stick a finger 1-2 inches into the soil and see if it’s damp. If it is, don’t give it excess water. 


The amount of water your plant needs will depend on its size. Larger plant = more water. 


When you’re watering weed, pour water around the radius of the soil (avoid pouring onto the leaves) and let it pool up. If you see water runoff from the bottom of the pot right away, the roots may need some time to soak. Come back in 15 minutes and pour more water until the entire pot of soil is soaked. 


Note: your cannabis plant should be equipped with plenty of grow room and good drainage to optimally soak up the water. 



When should you water your marijuana? 

The time of day is key to your weed plant’s water retention. Cannabis plants retain water better in cooler temperatures and hot air can cause water evaporation. Plan to water earlier in the morning or in the evening during the summer (if you’re growing outside). In the winter, wait until a bit later in the day when the temperature is a bit warmer before watering. 



What tools do you need for watering? 

Tools for watering cannabis plantsTypically, the watering process won’t require much. Just a pot, watering can with a spout, and spray bottle for misting your plant. 


However, you can find automatic watering systems that can be set to a timer and give your cannabis plant water automatically. These systems aren’t free so be mindful of the added cost!



What kind of water should you use for weed plant growth? 

Cannabis growers should take note that not all water (especially tap water) will be the same for cannabis plants. While most traditional tap water will be okay for weed plants, hard water can cause calcium build-up which is bad for your plant. 


The best water for cannabis plants is made through reverse osmosis water. This isn’t always easy to get ahold of in the large quantities you’ll need for cannabis cultivation since it’s generally bottled water, so stick to tap if you’re not in a hard water area. Otherwise, look into purifying your water. 



Additional considerations

On top of basic watering techniques, there are some additional hydroponic tactics you need to know – like flushing, soil type, pot size, fertilizers, and understanding pH level. Check the rest of our Answered blog series or subscribe to our newsletter for cannabis education straight to your inbox. 



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