Why Do Cannabis Plants Need Nutrients?

Cannabis plants require nutrients just like any other plants to survive and especially to thrive. However, feeding marijuana is a nuanced business. As both macro and micro nutrient requirements vary from strain to strain. Moreover, even different phenotypes of the same strain may have dissimilar nutrient needs.

The best way to avoid under or over fertilising a cannabis garden is to get nutrients dialled in from the very beginning. This means administering the right nutes at the right time. And if you keep reading you will.

Nutrients And Growing Cannabis


Naturally, nutrients must be included amongst the five key environmental factors of cannabis cultivation. Of all the five this one is 100% in the hands of the grower. Marijuana will give you subtle hints followed by not-so-subtle withering before it perishes. Most grow op kills are due to grower error rather than pests and pathogens. Usually, incorrect nutrient doses are the cause of death.

As eluded to above, cannabis plants fundamentally require specific ratios of macro and micro nutrients throughout their lifecycle. The 3 core macro nutrients for marijuana are Nitrogen, Phosphorus and Potassium. This trio is the N:P:K ratio listed on bottles of cannabis base nutrients.

Cannabis micronutrients are usually only required in trace amounts. They may not be required in high volume, but make no mistake they are still essential. Most high-quality base nutrients will satisfy cannabis plants trace element requirements. Infinitesimally small quantities of boron, sulphur, zinc and a few more elements, you vaguely recall from Science class, are blended into cannabis nutes as standard nowadays.

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Calcium and magnesium are the two that every grower needs to monitor. Soil growers are pretty much safe from this threat. But hydroponic and coco cultivators need to beware and take preventive measures. Investing in a bottle of cal/mag is wiser than worrying and watching for the signs of the deficiency progressing. Be a proactive grower as opposed to a reactive grower.

Cannabis also requires some supplements like beneficial fungi, enzymes, and silica to reach its full potential. Technically they are not cannabis nutrients instead they facilitate the absorption of nutrients. Not every weed grower swears by adding supplements but we strongly recommend them.




Cannabis seedlings require a minimalist approach. Rooting cubes, Jiffy coco coir pellets, Rockwool or light mix soil are the best starter mediums. Moderately fertilised seedling soils and rooting cubes typically contain sufficient nutes for the entire seedling stage. The grower simply needs to water the infant plants.

Inert mediums for coco and hydro seedlings means the grower must apply micro-doses of vegetative nutrients or specific seedling starter fertilisers from the get-go. As soon as seeds sprout, 10-25% strength nutrient is required.

Supplements like mycorrhizae and root building enzymes are most effective when applied early. Get your seedlings off to a flying start by focusing on root zone development.


Vegetative Growth


Base nutrients with a high N and low P and K are what cannabis needs in the early part of its lifecycle. Most branded fertilisers come in a one, two or three part set. In general, the grower must ensure the nutrient mix has as close to N:P:K ratio 2:1:1 as possible.

Although, some strains will prefer slightly adjusted ratios. Monitor post feeding behaviour closely, if it’s your first time cropping a particular strain. Incrementally increases doses of Veg base nutes as plants develop.



As cannabis transitions from vegetative growth to the bloom phase its nutrient requirements shift. During flowering weed is no longer hungry for N and the all important N:P:K ratio must be adjusted by the grower again.

1:2:2 is more appropriate as P and K are required in greater quantities so the cannabis plant can concentrate on bud production. Again some strains will need further N:P:K adjustment to find the sweet spot.

Too high N-levels will hinder flowering and tend to give buds a very green taste. N must be gradually depleted while P and K are incrementally increased. Cal/mag deficiencies may present in coco or hydro crops at this stage if base nutes are lacking.




The last two weeks or at least the final week of the bloom cycle must be reserved to thoroughly flush the cannabis garden. Regardless of the cultivation substrate, nutrients tend to build up over time and to make sure nuggs are the very tastiest they can be the grower must flush.

A light flushing solution or pure water works just fine for flushing plants. It’s so important to not overlook this final step. There’s nothing more disappointing than fat frosty buds spoiled by a harsh nutrient-laden flavour.


Coco And Nutrients


Organic cannabis nutrients are the best option for the soil cultivator. Nothing, absolutely nothing compares to organic dope grown in the dirt. Buy quality soil in the bag from the grow store or if you have plenty of experience under your belt mix your own.

Soil must drain well and have plenty of aeration. Often soil growers like to mix in a little coco for this very reason. Organic blackstrap molasses is chock-full of essential micronutrients and does a great job of feeding the microorganisms in soil. Don’t forget soil is a buffer for the root zone and is more forgiving than hydroponics.

Chemical nutrients will work well too. Just make sure the ratios are correct. The taste may be impacted but some inorganic flowering boosters really can dramatically boost yields. It’s up to the individual grower to strike the right balance.


Coco cannabis cultivation is the middle ground between soil and hydro. Once upon a time, the rule of thumb was treat coco like soil and feed the plants with chemical hydro nutes.

Fortunately, most nutrient manufacturers have recently released complete lines of coco specific fertilisers and supplements. Many are completely organic.

Now you can dial in the perfect coco specific nutrient mix. Don’t bother tinkering with nutes not specifically designed for the medium.

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Macro And Micronutrient Deficiencies Explained


Hydroponic cannabis cultivation, whether active or passive systems, respond best to chemical fertilisers. Organics in the reservoir is literally a recipe for trouble. Worse, the thicker consistency of most organic cannabis nutrients often leads to blockages in hydro irrigation systems. Always apply the nutrient line customised for use with your chosen growing medium.

Luke Sholl
Luke Sholl
Luke Sholl has been writing about cannabis, the wellness potential of cannabinoids, and the positive influence of nature for over a decade. Working with several cannabinoid-centric publications, he publishes a variety of digital content, supported by strong technical knowledge and thorough research.