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Water makes up between 80% and 90% of a plants weight.
Needless to say, H2O is pretty important when it comes to plants.
For cannabis gardening newbies, there are usually a lot questions when it comes to watering and feeding plants, such as:
"How much do I water my plants?"
"How often do I water my plants"
"Do I feed my plants with fertilizer every time I water?"
"What should the PH of my water be?
"What should the PPM of my water be?"
These are all very important questions when growing cannabis and this article will aim to answer all these questions and more, so you'll be on your way to becoming a cannabis wizard in no time!
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Water Quality
The quality of your water is vital.
Most of us home gardeners will be using city water out of the tap.
Tap water will work just fine, and actually has a lot of beneficial nutrients such as calcium, magnesium and in some cases potassium, but I definitely recommend running your water through a basic drinking filter or by adding a simple filter to your faucet before pouring it into your grow medium.
This will get rid of unwanted chlorine, and help lower the PPM of your tap water as well.
If you want to step it up a notch and have some extra cash you can purchase a Reverse Osmosis water filtration system. This will reduce and in most cases remove almost all sediment and unwanted contaminants.
I highly recommend purchasing a Reverse Osmosis water filtration system if you plan on taking a swing at growing using Hydroponics.
Plus, it makes for great, contaminant free drinking water as well!
Another option, is to simply leave your water out uncovered for 24 hours to let all the nasty stuff you don't want your plants drinking to evaporate.
How Much Water?
A good rule of thumb to follow is water about 10% of your pots size
For example: 10 gallon pot = 1 gallon of water
BUT...
What I have found works best, is to slowly water or feed until water starts coming out of the bottom of your pot.
Runoff trays should fill up about 10% to 20% after watering or feeding with diluted nutrient solution.
Watering until you see runoff is important because it flushes out whatever mineral deposits may be stuck in your grow medium.
How Often?
Typically you will need to water every 2 to 3 days, but this can vary depending on how well your roots are up-taking water and nutrients in your root zone.
A better way of determining how often you will need to water your plants is by doing the old finger test.
Stick your pointer finger into the medium, knuckle deep.
If you feel any moisture, from the tip of your finger to that first knuckle, your plants roots still haven't completely taken in the water or nutrient solution from your last feeding, so wait another day and check again.
PPM and PH are Key
PPM stands for parts per million.
This tells you how much stuff in the form of minerals, micro and macro nutrients are in your water or feeding solution.
PH refers to the acidity of alkalinity of your water.
PH is measured on a scale between 0 and 14.
0 being extremely acidic and 14 being extremely alkaline.
Getting the right PPM for the different grow stages of your plant, and balancing the right PH are integral to the success or failure of your harvest.
PPM
To show the correct runoff PPM per growth phase for Hydroponics and for Soil/Coco, I've provided a chart below
IMPORTANT: YOU NEED TO GET A PPM OR EC READING BEFORE YOU WATER AND/OR FEED, AND YOU NEED TO GET ANOTHER PPM/EC READING AFTER YOU WATER AND/OR FEED BY MEASURING THE RUNOFF.
Doing so allows you to diagnose the overall health of your plant and gives you an idea of the state of your oh so important root zone!
For example:
If your PPM of your nutrient solution is 800 and the PPM of your runoff is 600, that means your plants are absorbing a lot of the nutrients and your root zone is in great shape
On the other hand, if your nutrient solution PPM is 800 and your runoff PPM is 2000, there is a whole lot of mineral buildup in your root zone that should not be there.
In the high PPM runoff scenario, your next feeding/watering you need to FLUSH with pure water that has been PH balanced and do another runoff reading.
Keep flushing until your runoff PPM is in an acceptable range.
Another great option is to treat your plants with a flushing solution that contains enzymes that help break down mineral build up.
Advanced Nutrients Flawless Finish Flushing Solution, shown below, does just that.
PH
If you're growing in soil your max PH should range between 6.0 and 6.5.
For coco coir, your max PH range should be between 5.7 and 6.2.
And, for hydroponics your max PH range should be between 5.5 and 6.0.
IMPORTANT: YOU NEED TO MEASURE THE PH OF YOUR WATER AND/OR NUTRIENT SOLUTION RUNOFF BEFORE AND AFTER YOU WATER OR FEED YOUR PLANTS
Measuring the PH of your water and the runoff PH will provide you with a pretty good estimate of the acidity, neutrality, or alkalinity of your grow medium if growing in coco or soil.
For example, if you are growing in soil and your water has a PH of 6.5 and your runoff has a PH of 6.0, this means your grow medium is acidic.
Don't worry though! It's an easy fix!
All you need to do is, for your next watering/feeding raise the PH of your water.
Continue this process until your runoff PH is within an acceptable range.
Do the opposite if the PH of your runoff is higher than the PH of your water to correct the PH imbalance.
"Do I feed my plants with fertilizer every time I water?"
If your PPM is within the acceptable range per grow phase then the answer is YES go for it!
BUT...
Don't overdo it.
I've learned the hard way that less is more when it comes to feeding cannabis plants fertilizer.
Keep an eye on the PPM levels of your nutrients solution and runoff and adjust as needed.
Also, different strains, and the different phenotypes of those strains all feed and ultimately absorb nutrients differently.
Some can take in lots and lots of fertilizer and thrive and explode with new growth and huge buds.
While others, can be super sensitive to even the slightest bit of fertilizer and get nutrient burnt and show signs of deficiency.
Listen to your plants and remember less is always more!