A Beginner’s Guide to Cannabis Nutrients

03 Feb 2024

Cannabis plants require nutrients and minerals during their complex life cycle, and they can be provided organically or hydroponic applications. Having a thorough understanding of what nutrients and minerals cannabis plants require will give you an advantage when it comes to flowering and growing healthy plants. In this article, we break down the different types of plant nutrients, explaining the primary, secondary, and trace elements, flushing and our top tips to consider.

Organic nutrients
Most growers will start off using an organic growing medium for their first crop, with most sticking to soil ever since. Organic nutrients are available in either hard form or liquid form and will be absorbed by the plants once the soil has buffered them over a 72-hour period. 

Hard food examples 

  • Soil
  • Peat moss
  • Worm castings
  • Compost
  • Horse manure
  • Bone meal
  • Blood meal
  • Seaweed
  • Bat guano
  • Epsom salts

Liquid food examples

  • Fish emulsions
  • Seaweed extract
  • Worm castings tea
  • Molasses
  • Algae extract
  • Sugar beet extract
  • Humic acids
  • Fulvic acids
  • Bat guano
  • Seabird guano

Hydroponic liquid nutrients 
When buying hydroponic bottled nutrients that are ready to mix with water, they will usually come in a 3-6-part series, depending on the brand. These will typically consist of the primary nutrients N, P and K, as well as calcium, magnesium, and macronutrients. When making a nutrient solution with hydroponic liquid nutrients, it is essential to adjust the pH level accordingly between 5.5 and 6.0.

  • N-P-K base nutrient
  • Humic acids
  • P and K boosters
  • Enzymes

Raw salts for hydroponics
For those who prefer to get out the scales and measure their own nutrients, raw salts are an excellent solution. A grower can start from scratch and make their own nutrients for the relevant E.C level. Starting with raw salts can save money over time on shipping costs and allow a grower to have full control over what is fed to the plants.

Which nutrients do Cannabis plants use?
There are three groups under which nutrients fall: primary, secondary and trace elements. Cannabis plants will use all the listed nutrients as and when they need, with a higher dependency on some later in the flowering and ripening stages. 

Primary nutrients

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Secondary nutrients
  • Calcium (Ca)
  • Magnesium (Mg)
  • Sulfur (S)
  • Trace elements
  • Iron (Fe)
  • Manganese (Mn)
  • Zinc (Zn)
  • Copper (Cu)
  • Boron (B)
  • Molybdenum (M)

Are carbohydrates and sugars important?
All plants will produce sugars; however, feeding a high-carbohydrate feed will allow the plants to feed the microbes in the soil and help grow some seriously dense buds. Organic growers will find black strap molasses to be the ultimate carbohydrate-rich nutrient. High in sugar content as well as potassium and other trace elements, molasses is a simple and effective way to keep the soil food web happy and the microbes and fungi thriving. 

  • Black strap molasses are made from sugar cane or sugar beets.
  • Honey is also a great way to produce a carbohydrate-rich feed.
  • Sugars and carbs are what microbes and fungi in the soil eat.

Making cold-water extracts and aerated tea
One of the most effective ways to provide nutrients to the soil is to use cold-water extracts or organic compost teas. There are a number of organic substrates that can be used, including worm castings, compost, bat guano and seaweed, to name a few.

Cold water extracts

By using a sock or fabric screen bag tied to a stick, you simply allow, for example, bat guano to sit at the bottom of a bucket as the stick hangs over the top of the bucket. As the sock sits inside the bucket, nutrients are released into the water and can be fed to the plants.

Aerated tea

This method is more complicated but much more beneficial from a microbial perspective. Using an air stone, pump, bucket and water source, you simply allow the water to bubble for a 24-hour period. During this time, the microbes, fungi and beneficial microorganisms present in your organic substrate will multiply from millions into billions.  

So what is flushing, and why is it important?
Flushing cannabis plants requires using only plain water for the final 7–14 days of the flowering cycle. The reason for doing so is to cut off N, P and K, allowing the plants to break down chlorophyll production, causing the fan leaves to turn yellow and fade. The other main benefit of using plain water is that it cleans the roots and growing medium of any undissolved salts. 

Many will argue that flushing is a waste of time and makes zero difference, while other growers swear that it is a must and dramatically enhances the flavor and overall experience when consumed. It is best to use soft water or reverse osmosis water when flushing cannabis plants. Enzymes are also a great way to accelerate the washing process amongst the roots and allow substrates such as coco to be rescued for a second cycle after harvesting. 

  • All nutrients should be cut off during the final 14 days of flowering.
  • Plants will begin to fade and display an array of multiple colors.
  • Flushing also allows a grower to save money on nutrient use.
  • Some growers do not believe flushing adds any benefits at all.

Top tips for using nutrients 
Nutrients come in all shapes and sizes, with various numbers and values on the label. As a first-time grower, walking into a grow shop and seeing the huge selection of brands can be overwhelming. Here are our top tips to consider the next time you are about to invest in nutrients:

Top tip #1 - Avoid old nutrients
This refers to old bottled nutrients that have been sitting around for a long time and have started to compress. The same rule applies to soil, worm castings or compost that is lifeless.

Top tip #2 - Buy a pH and E.C pen
Hydroponic growers must always use an E.C pen to check the potency of their nutrient solution and make sure they are on the right track. Using a pH pen will give you a digital reading, giving you an idea if you need to add more salts or water to find the optimal range. 

Top tip #3 - Keep bottles away from sunlight
Exposing your nutrients to sunlight or a hot and warm environment will cause them to lose quality. Ideally, you should place your bottled nutrients off of cold floors and inside a dark and relatively cool cupboard area.

Our Conclusion
The best advice we can give a first time grower is to use soil and follow a feeding guide chart if using bottled nutrients as well. Growing cannabis organically is a slow and simple method that will ensure great tasting flowers and hash.

For those who are ready to make the jump from soil to hydroponics, we recommend learning as much as possible about the topic in advance due to the fast-paced and complex nature of the various hydroponic systems. Good luck learning which nutrients your plants need and why, and growing top-notch flowers!

If you're starting with the cultivation do not miss our complete guide on the use of nutrients in the cultivation of Cannabis.