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What Do I feed My Cannabis Plants?

Added 17 April 2020

When growing Cannabis it is very important to know what your plants need, at each stage of their life cycle. Having an understanding of which nutrients do what can give you a huge advantage when it comes to growing top-shelf flowers full of flavor. Below we explain how plants use nutrients when they depend on certain ones at different times and what you should consider when feeding your Cannabis plants.

Primary Nutrients

These will represent the 3 main nutrients that you will see on all nutrients bottles. The N-P-K value will display the amount of Nitrogen, Phosphorus, and Potassium present in the organic or hydroponic medium. For instance, you may have noticed on your organic feed the numbers 5-1-4. This will inform you there are 5 parts Nitrogen, 1 part Phosphorus, and 4 parts Potassium.


  • Nitrogen - Used to develop foliage, leaves, stems, and branches. Nitrogen is also responsible for the production of chlorophyll, which is used in the process of photosynthesis to convert energy, amino acids, and enzymes. The use of Nitrogen should be reduced once flowering has commenced.


  • Phosphorus - Alongside Nitrogen, Phosphorus will aid in healthy root development and allow the plant to grow thick branches that will support the weight of the flowers to come. Phosphorus is one of the main requirements when flowering Cannabis plants.


  • Potassium - Helping to convert Carbon Dioxide, stimulating foliar growth and an essential nutrient with Potassium when Cannabis plants are flowering. Potassium will strengthen stems and give the plants a healthy, strong growth structure during the vegetative stage.

Trace Elements Explained

On the back of the nutrient bottle, you will also find the analysis of trace elements next to the primary nutrients. As the name suggests, these smaller nutrients are required by Cannabis plants in much smaller ratios. The right ratio of trace elements is extremely important and can be the difference between an imbalance and deficiency or lush healthy growth.


Magnesium - Responsible for the function and production of plant enzymes, auxins, and stem growth. Works in conjunction with Manganese and Magnesium.

Calcium - Aids in the transportation of Nitrogen and sugars.

Sulfur - used to produce growth hormones and vitamins, and seen as an essential building block.

Zinc - Necessary alongside other trace elements for enzyme and chlorophyll production.Manganese - Dependent for the function of photosynthesis, and the production of enzymes.

Iron - A catalyst for chlorophyll production, also an element readily available to be absorbed by the roots.

Boron - Helps with Calcium uptakes as well as many other functions. It is an essential trace element that should be present during the entire life cycle of the plant.

Chlorine - Chlorine in the form of Chloride aids in photosynthesis, root production and functioning of the stomata.

Cobalt - A trace element that is required by the plants, however, many nutrient brands do add a great amount.

Copper - Acts as a fungicide and also benefits the root zone with enzyme production.

Molybdenum - A major player in the enzyme production and function of plants.

Nickel - Helps to break down Nitrogen and nitrates acting as an enzyme.


Hard Foods

When it comes to growing Cannabis using strictly organic substrates, most beginner growers will choose to feed only water. This is seen as true organics and will allow primary and trace elements to be utilized when required.

Complete Living soils will be available to buy from local grow shops and have been specifically manufactured for Cannabis plants in mind. Oftentimes there will be a liquid feed to use with the living soil, however, using only pH stable water is really required.

Compost that was made from organic waste will slowly breakdown over the duration of the Cannabis plant’s life cycle. Compost is also rich in Magnesium and teaming with beneficial bacteria and fungi that work together to break down the organic matter and convert it back to the root zone.

Worm castings are taken fresh from a worm bin are very beneficial for stimulating microbial life. Well balanced in N-P-K as well as trace elements, using worm castings is a safe and hassle-free way to grow happy and vibrant plants.

Diatomaceous earth is a compressed stone that is high in Silica and will leach nutrients back to the soil. Also, an excellent way to prevent bugs infesting your soil as well as improve drainage and air capacity around the roots.


Liquid Foods

If you have decided to invest in liquid nutrients and are guided by a feed chart, then you will notice each of the various nutrients are designed for different stages of the plant's life cycle ranging from a rooting booster, vegetative feed, flowering feed, and some type of bloom enhancer or ripening product.

Liquid feeds created for soil application will often be molasses made from sugar. Other times they will be humic acids, worm, or bat guano extracts. When using liquid feeds, it is important to follow the nutrient chart and be sure to flush the plants correctly.

What Is Flushing? 

This means the time frame where the plants are flushed out of any undissolved salts that have built up in the growing medium. Additionally by feeding only plain pH adjusted water, the plants will naturally use up their internal reserve allowing them to give a final push prior to harvest.

A grower should allow the final 14 days for the plants to be fully flushed. There are many benefits to flushing Cannabis and they are:

  • Dramatically improves the flavor of the flowers once dried and ready to smoke
  • The ash will become a light, fluffy, and soft grey quality when smoking.
  • The plants will have the opportunity to have used up all reserve nutrients.
  • No need to use nutrients during the final 14 days of the flowering period.



Feeding Cannabis plants is a simple and straightforward process, especially when following a simple organic recipe using only water, or guided by a nutrient-feeding chart. Having the ability to diagnose when a plant is deficient of nutrients and acting fast will be a key player in how successful your crops are.



Flushing does not improve the quality of marijuana :thinking_face:

Show all replies (2)

@MobyDick420ESP, you must have never had harsh, gross cannabis then


@MobyDick420ESP, Reality works on cause and effect. Even if we don't know all the causes and effects.


@Nobody01,All the reason, one cannot trust anything on the internet, but equally if someone has an excess of fertilizer in the ground, doing root washing could be a good idea, but doing root washing the 15 days before cutting I don't think they will improve the flavor or quality, I prefer not to water it for 15 days before cutting to stress it in a positive way


nowadays we have it so good...if it's soil or coco or hydro...the many and competitive producers are making it so easy for us. Their solutions are so well made and with so little input, the plants can thrive easily.

One thing is worth chatting about, something that is above the average daily plant feed.
Let's talk about Ormus(Orbitally Rearranged Monoatomic Elements), let's talk about alternative growing. I have encountered on growdiaries and not only some master growers with unimaginable results from feeding Ormus to plants.


Thanks guys, that was a good beginners read I would say! :wink:
A few questions come to mind:
When to start feeding?
How much to feed according to the different plant development stages?
Watering with plain water is not really feeding, is it?
What about feeding when using tap water vs. RO water?
Does organic feeding need ph-ed water/nutrient solution? Doesn’t the micro biology of the soil self regulate the Ph?


RploccultGreen420, I systematically use ormus in the irrigation of my crops in concentrations of 1 to 1.5%. It is a permanent contribution of magnesium and calcium in addition to minerals in monoatomic mode.

I dedicate special interest to the water I use, usually collect rainwater that I mix with alkaline spring water (PH 9.2 EC: 0.85) at 25% to ensure the contribution of calcium and other minerals, when I do not have rainwater I collect water from rivers and springs with maximum concentrations of EC: 0.3, I always structure the water with a magnetic stirrer, before adding nutrients.

I make my own substrates, where 50% is reused land from other crops, I also add various minerals, organic matter and MM.

For direct nutrition uses my own specialized soluble and solid fertilizers, all made with organic raw material, minerals and residues (Humates, hydrolates, fermented, auxins, MMA, BAL, etc.), I also use solid inputs on surface every 15 days coinciding with the beginning of the growing and waning moons. I maintain constant and varied feed during all crops and a generous mulch layer composed of dry leaves, roots and stems of previous crops, this layer is very useful for my culture mode, first it is food for the MMs of the soil that remain active as long as there is moisture and that will make soluble the nutrients of the matter organic and minerals of the substrate, in addition, mulch maintains moisture on the surface and causes the upper roots of the plant to remain active and populated, usually when the soils are not covered, roots are not found in the first centimeters of the substrate because regularly this part remains dry.

I usually irrigate crops always with acid pH between 6 and 6.4.

The solid surface inputs and the minerals of the substrate guarantee me all kinds of trace minerals. For the essential elements NPK I try to look for different and varied sources for each element and I compose the irrigation of the day depending on the stage of growth. For example: The N I get, always organic and not ureic, I get it from residues of sheep wool, ox hooves, alfalfa flour, fish meal, dried blood, etc. Phosphorus is the most difficult element to make it assimilable immediately by plants, I make fermented and bioles where I soluble phosphorus from: Phosphoric rocks, animal guanos, bone flours, etc. The last element, Potassium, the truth that potassium is present in countless mineral and vegetable sources, this is a very important element. soluble, I contribute potassium in solids and liquids, I make fermented, dehydrate the skins of fruits and convert them into powder, use various types of ashes, etc. With all these elements separately I compose my fertilizers, trying to give a varied diet every day of watering.

I am currently experiencing several techniques that I explain in my journals.
I am happy with the harvests and the quality I get and try to improve day by day. I don't do root washing. Greetings



when to start feeding: depending on what type of grow substrate you use for your grows.

How much to feed...usually the nutrients that one uses come from producers who usually are kind to supply feeding schedules for best results. You can follow that as a guide to which you adjust based on the plants response, the ph, EC etc
Watering with plain water is feeding, but not in the sense of "nutrients". Water needs to contain oxygen, which is vital for the plant, has to have a certain pH, water is a ph adjuster as well. Also if it happens to grow in soil and if the soil is prefertilized, then watering is feeding (in the sense of nutrient feed)

Tap water vs RO water... question is water vs RO water vs magnetic water ; worth doing a research paper on the subject

Not really a need of ph-ed water in organic growing, only if you know the soil that you work with is either too alkaline or too acidic.
If it's contained organic soil growing you can use tap water with huge success, but make sure you water until you get some run off that you get rid of and prevent nutrient lockdown. The water with nutrients while in the evaporation and absorption process will change to alkaline status which will eventually affect the plant...starting with the iron (Fe)


Flushing is modern day magic. My ash is grey-white and i don't flush. I have no chemical taste. Do you know what cell differentiation is? buds don't store that shiz. that's not their biological function.

when you body has an excess of something, do your organs all of a sudden become partly composed of that something? lol. no, it's stored in cells diversified to handle that sort of function. it doesn't just go everywhere willy-nilly, ffs.

that's liek hearing someone say "roots selectively absorb... " no.. no .. no... you know immediately to stop listening to the monkey that never took a biology class in their life. or "it activates..." bWAHAHAH not a scientific term used by anyone with integrity.


@CannaFun, Well-educated doctors in the 1800s put leeches on people for medicinal reasons. Under that logic, we'd still be doing that, now.

Flushing may or may not be beneficial, but it certainly doesn't impact the mineral content of the buds in any major way. it's been proven in lab studies involving equipment that the human eye cannot compare.

It doesn't impact ash coloring. It shouldn't impact taste unless it, as usual, overfed. It doesn't impact mineral content of the buds. So, when someone lists some causality and the why and how, then it might not be magic or personal beliefs based on their own behaviour. just like 90% of all intiial studies published are later proven false.. 99% of holistic health is nonsense, and that's being generous.

I bet the people you list don't use these reasons to advocate it, but unless causality is researched it is a guess at best. It's more likely just one more oversophisticated thing people do when enamoured with a hobby.


@Nobody01, I will trust Ed Rosenthal, Jorge Cervantes, and SubCool over anyone else because they are certified and published growers that are famous around the world...


Good read.
Take what you read with a grain of salt and do your own studies!
To any new grower learn the basic science of the plant.
Try to grow as your doing so learn from reads and other growers but remember only to take what is valid to you. Take notes of the things that stand out and every move you do when growing the plant.
It’s not rocket science but it is nice to go back on notes to see our fails and our corrections.
You will learn through trial and error.
Happy cultivating everyone!


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