by Nebula Haze
Get answers to common questions about cannabis nutrients!
With any nutrient system you're trying out for the first time, I highly suggest starting at half the recommended nutrient levels when growing weed.
Only increase the concentration of nutrients if you see signs of nutrient deficiencies.
This is because, for whatever reason, most nutrient recommendations are way too strong for growing most strains of cannabis. (Maybe nutrient companies want to sell more by having you use more?)
So if the included nutrient schedule say add a teaspoon to a gallon of water, I'd say you cut that in half and add a ½ teaspoon to a gallon of water. If it says to add 2ml to a liter of water, than you add 1ml to a liter of water.
With nutrients, a little bit goes a long way.
I've found over and over that you get the best yields by erring on the side of "too little" over "too much" nutrients. I always start a half strength and only move up when I see deficiencies.
For example, I do increase nutrient levels if I notice slight yellowing of leaves towards the bottom of the plant.
Increase Nutrient Levels If You See This
Now yellowing leaves towards the bottom of your plant is okay if you're late in the flowering stage, but this symptom needs to be corrected at any other time earlier in the plant's life (to make sure you have enough leaves that last all the way to the end).
How much is too much nutrients?
I recommend providing just enough nurients to avoid signs of underfeeding. I tend to start nutrients at half-strength and only raise the strength if I noticed signs of nutrient deficiencies(usually starting with pale or yellowing lower leaves).
Some growers try to “push the limits” to feed as much nutrients as possible without causing nutrient burn. I recommend against this method because nutrient burn is permanent – if you burn your plants, all those leaves will be permanently burned. If buds have already started forming, you can cause nutrient burn on your actual sugar leaves on your buds, causing the appearance of your harvested buds to appear rough, even if the buds themselves are fine.
For hydro growers, checking the PPM of your water is one of the best ways to see whether your plants need more or less nutrients. Learn more about PPM in hydro here. For a hand-waterd plant, one of the best thing to do is check the PPM of both your nutrient water going in and the run-off water coming out the bottom. So for example if you add nutrient-water at 1000 PPM and watch the run off you'll be able to track the change; if the PPM goes up it’s clear there is enough nutrient already, perhaps even too much. If the PPM drops, you know you can continue with feeding because your plant is taking in enough nutes to prevent any from being left over as extra.
When should I stop fertilizing during flowering? Not one website or blog has given a definitive answer. Is a nutrient "flush" necessary?
Lots of growers have different opinions about when to stop fertilizing during the flowering stage, and unfortunately there's no consensus. Many growers fertilize differently from each other and no one agrees one what's the right way. Some growers fertilize until the end, and some stop giving nutrients for days or weeks before harvest time.
If you're growing in soil, growers usually stop giving liquid nutrients sooner than in hydro. I've heard of soil growers flushing (giving just plain water) for up to a month or more before harvest time, or even longer. This is because there is likely some amount of nutrients contained in the soil.
In hydro, most growers will flush (give only plain, pH'ed water) for 7-14 days.
I would make sure you provide flowering/bloom nutrients for at least the first 6 weeks of flowering, or longer. A common technique is to flush your plants for 2 weeks before harvest. So basically you wait until you think your plant is almost ready, and start flushing (giving just plain water with no extra nutrients).
When it comes to nutrients, I personally try to give as little nutrients as possible during the second half of the flowering stage. As long as you aren't seeing deficiencies, you're giving enough nutrients and there's no need to go up. By providing relatively low levels of nutrients, you aren't building up extra nutrients in the plant which could affect the taste of buds.