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What are the best nutrients for growing cannabis?

July 21, 2016

Updated 03/22/19

For the first-time grower, it can be a truly daunting task to select the best nutrients for their cannabis, and they’ll often spend far more money than they need to. With so many options to choose from that range from hydroponic to organic nutrients, new growers can quickly get overwhelmed. But with a little bit of knowledge about the requirements of cannabis plants and how they absorb and utilize nutrients, you can confidently select the products you need without breaking the bank.

Which elements does a cannabis plant need?

Periodic table of elements

Your cannabis plant needs a main group of elements that are collectively referred to as macronutrients. Here’s a breakdown of the mineral and non-mineral elements you need to feed your plant.

Mineral nutrients obtained from the soil:

  • Nitrogen (N)
  • Phosphorus (P)
  • Potassium (K)
  • Calcium
  • Magnesium
  • Sulfur

Nitrogen

Nitrogen is mainly responsible for a plant’s development during the vegetative stage of its life. It’s an essential part of chlorophyll and without it, a plant can’t turn sunlight into energy and it won’t be able to grow.

Nitrogen is also part of the amino acids that act as building blocks for proteins in a plant. Without the necessary proteins, your cannabis plants will be weak and frail. Nitrogen is also a part of ATP, which allows plant cells to control the use of energy.

Nitrogen is also necessary to create nucleic acid, an essential ingredient in DNA or RNA, and without it, cells won’t be able to grow and multiply.

Phosphorus

Phosphorus is important for producing large, healthy buds. The key role of this element is to help make nutrients available for the plant to uptake. These nutrients than are used to build the structure of the plant as it grows from the roots to the flowers.

Without adequate phosphorus, plants will show signs of undeveloped roots and might not even flower. Early signs of phosphorus deficiency shows up as a purple hue in the veins of leaves.

Potassium

Potassium has a number of jobs that largely help to regulate the systems that keep a plant healthy and growing. It plays a large role in osmoregulation, the passive regulation of water and salt concentrations in the plant. Potassium accomplishes this by controlling the opening and closing of the stomata which is how a plant exchanges CO2, H2O, and oxygen.

Potassium also triggers the production of ATP, which works to store energy produced in photosynthesis by creating glucose. This glucose is then used as energy for the plant as it grows. Without sufficient potassium, you will see weak plants starved for energy that appear burnt because they are unable to successfully regulate the exchange of CO2, H2O, and oxygen.

Calcium

Calcium is responsible for keeping the structure of cell walls in a plant together. Without calcium, new growth won’t develop properly and the plant won’t function as it should. New growth will be stunted, leaves will curl, and rusty spots will show up on the plant.

Magnesium

Magnesium acts as the central molecule in chlorophyll and without it, plants aren’t able to generate the glucose from photosynthesis. No magnesium means no energy can be converted from sunlight.

Once magnesium has helped create glucose, it helps metabolize glucose to make it available for the plant to grow. Without sufficient magnesium, you will find yellowing leaves, with discoloration reaching the veins as well.

Non-mineral elements derived from air and water:

  • Carbon
  • Hydrogen
  • Oxygen

Root Rot, Mildew, and Leaf Septoria: How to Deal with These 3 Cannabis Plant Diseases

How to use nutrients

The three numbers shown on the front of fertilizer bags, nutrient solution bottles, or other additives indicate how much of the three main elements (nitrogen, phosphorus, and potassium) is available in the product. For example, a product that says “10-4-4” will contain 10% available nitrogen, 4% phosphorus, and 4% potassium by weight. These are always listed in the order of N-P-K.

All other mineral nutrients are grouped into the category of micronutrients, as they are used in much lower quantities. This group consists of the following elements:

  • Zinc
  • Iron
  • Manganese
  • Molybdenum
  • Chlorine
  • Cobalt
  • Silicon
  • Boron
  • Copper

When is the Right Time to Harvest Cannabis?

While cannabis plants require very low concentrations of these elements to thrive, they are still vital to the overall health and growth of the plant.

Next, we’ll examine the main types of nutrients used by cannabis growers today as well as their proper application. Before you start growing, however, we highly recommend learning about the basic mechanisms through which plants absorb water and nutrients, osmosis and active transport.

Hydroponic (soilless) cannabis nutrients

Hydroponic grow system for plants

Hydroponic growing is simply the practice of growing plants without soil, usually with some other sort of substrate like rockwool, clay pebbles, coco coir, or some sort of mix. Many of the premium “potting soils” marketed for growing cannabis are actually soilless blends. Most indoor cannabis growers are growing hydroponically, even if they’re using buckets of “potting soil” and hand watering each plant.

For this reason, the vast majority of the nutrients sold specifically for cannabis cultivation are hydroponic nutrients. These products are comprised of concentrated mineral salts, usually in liquid form but sometimes as powders, that are to be diluted in water to a level that is suitable for the plant.

Spider Mites, Fungus Gnats, and Root Aphids: How to Deal with 3 Common Cannabis Pests

Nutrients must be water soluble in order for the plant to absorb them. Liquid products are sold in two parts (usually labeled “part A” and “part B”) because they contain elements that will precipitate out of the solution if mixed together at a high concentration, making them unavailable. Combined in the correct volume of water, this is not an issue.

Products are also divided between “Grow” solutions, high in nitrogen needed for vegetative growth, and “Bloom,” high in phosphorus for flower development, because the cannabis plant has different nutritional needs during different stages of growth.

Great care should be taken when applying hydroponic nutrients, as overfeeding can lead to plant damage and even death. A general rule of thumb is to start at about 25% of the level recommended on the product label and gradually work up to full strength. Hydroponic nutrients are often used by soil growers with good results, but this technique is not recommended for the beginner.

Soil nutrients and organics for cannabis

Soil for plants

What sets soil apart from hydroponic media is the presence of non-inert organic matter like humus, compost, manure, and worm castings that contain many macro and micronutrients. Much of the nutritional value in these substances is locked up in non-soluble form, however, and must be processed by soil-dwelling microbes and fungi in order to be of use to the plant. Non-organic nutrients designed for soil growing are less common at the grow shop because they can quickly build up in the soil, harming the soil life as well as preventing the uptake of water and nutrients by the root system.

Organic fertilizers and nutrients for cannabis are far more forgiving; they usually contain less immediately soluble nutrients and more elements that are beneficial to soil organisms. The first-time grower who decides to use soil as their medium would be well advised to stick to organic fertilizers and nutrients.

Greenhouse Cannabis Cultivation: What are the Benefits?

The least expensive way to do this is to use things like blood meal and fish meal for nitrogen, bone meal and bat guano for phosphorus, wood ash and kelp meal for potassium, dolomite lime for calcium and magnesium, and epsom salts as a source of magnesium and sulfur. Most of these items can be purchased cheaply at your local home and garden center and then mixed in small amounts into the soil before potting. Done correctly, you’ll only need to water your plants and occasionally add carbohydrates to feed the soil life. There are also commercially available soil blends that already contain the proper mix of these types of ingredients.

Alternately, there are pre-mixed organic nutrient solutions you can buy that take the guesswork out of feeding your plants. These tend to be expensive, but the benefit is that you can simply follow the manufacturer’s feeding schedule and get good results.

Growing Organic Cannabis at Home

The key to successful organic growing is cultivating a diverse and healthy population of soil microbes and mycorrhizae in the soil. Many premium soil blends come pre-inoculated with these organisms, and there are many (often expensive) additive products available that add additional life to your medium. However, the best (and cheapest) method of inoculating your soil is through actively aerated compost tea (AACT), something you can make yourself with just a few inexpensive items. By using this technique, you may find that you don’t need to add very much in the way of nutrients or fertilizers; the soil life will process the organic matter in the soil into nutrition the plant can readily absorb.

There are many ways to grow cannabis, and each has its benefits and drawbacks. Organic soil is more forgiving of mistakes and less than ideal conditions, but often produce smaller yields and slower growth. Hydroponics and synthetic nutrients can offer bigger yields and quicker flowering times, but require a great deal of attention and knowledge to be successful. The best advice for the beginning grower when selecting nutrients and fertilizers is to make sure you’re using products that are compatible with your technique and medium, as well as with each other. Doing a little research before your first grow can prevent wasted money spent on unnecessary products. Happy growing!

Indoor vs. Outdoor Cannabis Growing: 3 Key Differences

  • h311sdr01d
    • Little Lord Kackenackt
    • Lenroc

      I see most fo the Roots Organics include Molases, while the rest of the contents the bat and bird guano seem to be awesome I have to ask where does the Molasses come in, we know plants do not absorb sugars from the ground and it actually impedes root growth and seed start http://www.biology-online.org/biology-forum/about10736.html so why would you do that to your crops.

      I myself go the other route with a clean and known quantity of substances so I get same results everytime. I use Cogo’s Original Cannabis Fertilizer Formula from CogosOriginalCannabisFormula.com and some of the results have been simply incredible. It’s so clean I even seen an aquarium use movie of it… for aquaculture with a bunch of fish swimming around and beautiful plants.

      • Two Bears

        People say that sugars really enhance tge amoubt of trichomes.

        • cdee von

          Sugars feed the microbe herd..

          • Rich

            Yes that’s absolutely true. Its actually the carbohydrates that feed the soil.

          • max’s pad

            I keep reading about molasses, but I am skeptical that it may just be rumor repeated until it seems factual. Does anyone have a scholarly article that would support this?

          • Igor Mini Chornyvolk

            Youtube good green earth company use with bokashi

        • Igor Mini Chornyvolk

          Try Bokashi with some blackstrap molasses. 1cup bokashi 2 ozs molasses to 10 litres water

      • Rich

        Molasses is used for it’s natural sulphur not it’s sugar.

        • cdee von

          The sugars feed the mycorrizae and the beneficial microbe herd
          .

    • Melvin S Edgmand

      I agree 100%

  • Little Lord Kackenackt

    I started using Tasty Garden single tank professional fertilizers. It is the best fertilizer I have ever used. It works great in soil, coco coir and hydroponic systems. They offer a fertilizer for vegetative – Plant & Grow, one for flowering – Fruit & Flower and a bud booster – Size & Flavour. I have used many ferts over the years and Tasty Garden is the one to use if you want big, strong healthy plants with awesome yields.

    • Gwennie

      Can you purchase this in the U.S. and what website did you use?

      • Little Lord Kackenackt

        I had a friend purchase it for me in Europe and UPS it over to me. I bought 1 kilogram of the vegetative, 2 kilograms of the flowering and 250 grams of the bud booster. You usually use more of the flowering fertilizer than the vegetative fertilizer and you only need the bud booster for the last several weeks of growing. Best fertilizer I have used- dissolves quickly and is pH neutral.

      • Rita Rochester

        You can buy them from amazon – Here read this https://theweedprof.com/best-nutrients-fertilizers-cannabis/

  • Alex Dubois

    Good article about growing cannabis. I didn’t really think about the fact that growing in a soilless medium was a good opportunity to use hydroponic nutrients. It’s more forgiving than straight nutrient solution alone since the organic matter can buffer some of the nutrients allowing for easier plant uptake.

    While it is true that you can grow cannabis with just the nutrients mentioned in this article, the often overlooked component of plant health is trace minerals. These are minerals that are only available in parts per million or parts per BILLION! The presence of a wide array of trace minerals will give the plant the ability to “express its full genetic potential.”

    The only organic fertilizer that I am aware of that includes ALL 72 trace minerals in a plant available form is MightyGrow Organics Living Organic Fertilizer 4-3-4. It is available online from mightgrowfertilizer dot com (not the company’s website) or from a local garden center. If they don’t carry the product, ask them to get in touch with the company at mightygrow dot com.

    As far as liquid organic fertilizer, two formulas will be available in the spring. A 3-1-2 “grow” formula and a 1-3-2 “bloom” formula. Additionally, a minor mineral, trace mineral, humate liquid is in development. A long time west coast grower has been interviewed about his experiences with using MG’s products. Check on the company website to watch. It should be uploaded by Jan. 1, 2017.

    • SavageHippie

      Milorganite is NOT a certified organic fertilizer. It is processed human
      SEWAGE! There are plenty of real organic fertilizers, several of which
      are mentioned on this site. I manufacture MightyGrow Organic products,
      which are USDA/OMRI listed as allowable in organic food production. You
      should use nothing less than REAL organic fertilizer to grow cannabis.
      And MightyGrow is the only product that contains all 72 minerals needed
      to grow cannabis to its genetic potential.

      Care for this guys posts, appears to be dishonest, check comment of his few lines below.

  • T-DOG

    coffee grounds.crushed egg shells,hydrogen peroxide,wood ash,epsom salt,home made bone meal,willow tree tea [one of the best all natural root
    enhancers on earth] so much cheaper to go all natural things…you have the internet.look up how to make natural fertilizers

    • love.violet524

      How Encouraging!! I instinctively added crushed egg shells and coffee grounds to my pot (in the lower third of a three-gallon pot), and I have a native CA Willow in my garden! My heavy black clay soil is full of earthworms, and I plan to give some a new home with my little baby purple gorilla. 🙂

      • T-DOG

        im glad you are using more natural things to feed your baby,good luck.I forgot to add epsom salt in my post..farmers have been using it for many years

        • love.violet524

          Epsom salt may not be ideal for all soil combinations, anyhow. I’d be inclined to think of it as a remedy if the plant looks low on magnesium and the other trace nutrients. Salt can be rough on roots, I think. Maybe I’m wrong about that… 🙂

          • T-DOG
          • love.violet524

            I’ll try this when Purilla gets a little bigger. I like this video! … especially that ‘special’ shot 😀 My soil is very alkaline. My pine wouldn’t have made it, and my roses struggle without chelated iron. I grow parsley, and I think I’ll add that to my tea concoction for some potassium, phosphorus, calcium, iron, and other good stuff. Keeping it organic is a challenge… Thanks T-Dog!! 😀

  • BioaktivFertilizers@gmail.com

    I make my own fertilizers now days and compost, worm castings teas 2-2-2 for veg , and atlantic seaweed from Nova Scotia for flower 1-.5-3 , can you say quality !! Let seaweed soak and breakdown for 3-4 months in a bucket with a small stone bubbler ,

    Worm castings ,let it brew for 24 hrs with 1 tsp of molasses . 1/3 cup of castings per 1 litre will give an ec of around .9/1.2 all depending on how you fed the worms . Best get a good book on composting nutritional values, i make my own casting

    In hydroponics and coco i use Remo Nutrients , very good quality and very decently priced !!!

  • Two Bears

    I want to set up a worm farm and use worm castings.

    • Melvin S Edgmand

      Iam i. Oregon and my friend has just begun with his he has like 4 different beds and he cant sell it fast enough mostly to california growers the wanna buy the worms dirt castings but he only sells the castings for 12 oz container he gets 7.99 good biz to get into

  • Elizabeth

    hi can anyone help me with tips and advice on growing and how to succeed? i have month old plants in organic soil only on window ledge just watering , not feeding. what is best now in terms of feeding and where to grow them? like outdoors in greenhouse or in woodland nearby? or in a greenhouse in my back yard or inside in a tent with lights? whenever i have tried outside before they died. i live in northwest of england uk often rains and no sun,
    i bought these seeds from holland when i went over in april, i really want the plants for all kinds of reasons, smoothie making freezing the leaves and smoking too, any advice to help me would be much appreciated. thankyou in advance
    elizabeth

    • Aaron Frings

      first you need to communicate with the seed bank and find the recommended strain for your climate. Hombolt county California produces some of the best in the world and it always rains and is only sunny about one month a year. I use happy frog soil with organic nutrients with low numbers .. If you start your seeds early and let the seedlings grow about 20 centimeters or bigger and then put them outside as the weather feels more like spring.I use 200 gallon smartpots ,the bigger your pots the bigger the plants and dont forget to purge your soil once a month .. even organic nutrients will build up in your soil.. that means water your plants for several days with no food to flush the buildup.. when the plants flower they like sugar ..i use molasses .. will help the flavor.. when feeding my plants I look at the color , especially the new growth.. if it is lighter color than the rest or the whole plant or closer to lime green i will feed those plants more.. some plants cant take much .. you will notice these plants by the dark green color.. if your leafs start to curl and the plant is dark green back of of the nutrients those are signs that your are over feeding. also while the plant is in veg stage composted chicken shit works great.. sprinkle a thin layer over your soil a couple times then back off when flowering.. it will lower the taste quality of your bud.. but keep worm castings on them all year.. hope it helps some .. good luck… ps feeding young starter plants can kill them.. let them get at least 30 cm first

    • Matt

      I was a total noob and got the Three A Light book and they just got an app too! So I can message them or call them directly for help.

    • Dee C

      Check out youtube , there are many many videos on the subject. I researched for many months prior to starting my own grow . It is my first time and so far , so good. I started buying equipment and have made my own home made compost already for tomato garden and used it in my soil . I use an all organic blend with worm castings in it and add some of my own worms to it along with shredded organic matter they can break down over time. I let that set for about 6 weeks , and mixed in some perlite for drainage . I also joined several groups on facebook. I would research and weigh the information with what I already know about organic gardening and chose a couple to get reliable information and tips from some of the members. One thing I learned and I swear by it is cows blood. Yep, cow’s blood. Works great and can be added from day one up to the final flush. Check out Charles Marcheterre on facebook. His grows are awesome and he uses the cows blood and has videos on how to use it . Good Luck and Happy Growing.

  • Kel

    Hi, I’m using foxfarm ocean forest potting soil and I was wondering can I use Flower Fuel and Cal-Mag Plus to my foxfarm trio ( Big Bloom, Grow Big and Tiger Bloom) to help my plant to flower.

    • Jamil Dotson

      You sure can…I’m actually running that in my grow as we speak

  • Jeffersonman

    I would warn people that there a lot of pot businesses out there that are trying to sell their products, to make some quick bucks. Selling products has not changed much. People literally buy things that claim their product is the “new” quick fix that solves all your problems fast, and with little effort. Look at the so-called fitness industry. People have made millions selling “Voodoo” products that are not regulated, and claim outrageous results that you pay big bucks for when there are natural products that do the same thing for cheap.
    Learning a little bit about soil science can go a long way to creating a better soil with cheaper organic methods. A good compost, and potting soil, along with Alaskan Humus, worm castings, kelp, and a good organic fertilizer like Milorganite is all you need for a healthy organic mix that will satisfy just about any plant’s needs. Learn to make compost tea and you have it pretty much all covered. Chemical products are expensive and are unfriendly to the environment. Unless you are a commercial grower stay away from chemical and go organic.

    • Tom Boyd

      That is the best advice I have seen, ever!!!!

    • Alex Dubois

      Milorganite is NOT a certified organic fertilizer. It is processed human SEWAGE! There are plenty of real organic fertilizers, several of which are mentioned on this site. I manufacture MightyGrow Organic products, which are USDA/OMRI listed as allowable in organic food production. You should use nothing less than REAL organic fertilizer to grow cannabis. And MightyGrow is the only product that contains all 72 minerals needed to grow cannabis to its genetic potential.

      • SavageHippie

        The only organic fertilizer that I am aware of that includes ALL 72

        trace minerals in a plant available form is MightyGrow Organics Living

        Organic Fertilizer 4-3-4. It is available online from

        mightgrowfertilizer dot com (not the company’s website) or from a local

        garden center. If they don’t carry the product, ask them to get in touch

        with the company at mightygrow dot com

        Find it strange that in your post above you distance yourself from your own company hmmm.

  • Putnam Lisa

    Personally a big fan of the Happy Frog fertilizers from Fox Farm, and good ol’ Maxicrop… Maxicrop, or Norwegian sea kelp is a great trace minerals fertilizer/supplement with a little bit of potassium as well. I have seen times personally where a cannabis plant is not growing with the optimum health and vigor, then simply maxicrop (sea kelp) was supplemented to the weed plant and in a matter of hours that plant’s color had changed to a deeper green and had visually gained vigor, eventually flowering and finishing up into some heavy yielding, big-budded chronic. Sometimes the small things may be overlooked in certain soils, adding sea kelp into your soil or onto your plant(foliar feeding) is a reliable way to ensure that hungry cannabis plants get the nutrients they need to grow big and yield hard.
    Forget to say, my MEIZHI LED grow light make great contribution to the big tight bud! lol

  • Gil JOHNSON

    Hydroponic does Not mean “growing without soil .”
    It actually means growing in water . Soil , leca or hydroton pellets , sand , Even glass … are considered mediums . Mediums are what the roots hold onto in order to support it’s own stalk , leaves or foliation and or buds and flower. In fact if given the space to due so the root mass will replicate the size of the plant length and width of the plant itself. Hydroponic systems do use mediums in not of the systems out there except maybe areoponic or if a areo-cloner or propagation machine is used to root cuttings .
    With soilless mix , and top feeding isn’t hydroponics , but place the pots or bags with soilless in a flood and drain or ebb and flow system and, voila! Growing hydroponically . In the very beginning , organic and hydroponic where two things not crossed together. Hydroponics increases the amount your able to directly feed your plants . With that dyntethic nutrients were made to help the plants increase the speed in which they grow as well . I won’t get into the whole organic / synthetic part of the hydroponic… but will say by using synthetic nutrients you helped feeding the plant as the plant does not have to search for the food as it is constantly flowing by or brought to the roots via flood and drain , nft, areoponic etc … that being said the plant now also didn’t have to work hard to process the organic foods to it’s synthetic form to use it as it was already done . Ie synthetic foods .
    Hydroponics is awesome way to grow and very fulfilling as you can see results hourly ! Especially areoponic . Anyways I can go on and on but gotta get back to hydroponic garden lol . I will say pick the right system that works with the time you wanna work on garden daily . . Q

  • gnarly dude

    Techna flora bc grow boost bloom gave monster yields.

    Ionic is a simple one part nutrients system.
    Advanced and canna are expensive but some of the best.

  • Kevin Sarsfield

    Hi Everyone, I’m BigK and am totally new to this. I am seeking advice( what’s new you say). I am growing for medicinal reasons to obtain eventually CBD oil from my crop. I am growing Master Kush in my greenhouse and have no doubt made a ton of mistakes, BUT, my plants are big and very healthy. In fact they are getting to big now and I need to keep them down in size so prying eyes do not spy them. I have been topping them constantly but they are still over 6ft tall and growing strong and bushy. I am worried that if i keep topping them they will never bud. Any ideas guys n gals? many thanks K

  • cat cat

    General Hydroponics and botanicare is now owned by Scotts Mircle Grow and they run tooo salty.

    Try House and Garden

    Humboldt Nutrients- especially the Humboldt Natural Grow/Bloom ( big boy stuff… the smell is overwhelming but the flowers stack so well)

    Canna always heavy yields.

    Technaflora, Roots Organics, FoxFarm , all great lines!!!!

  • Michele

    I am using Bountea compost tea, I feed this to my roots. M-3 for veg, B-3 for flowering I feed this through the foliage, I make my own medium primarily CoCo, Humus (Alaskan) bio-charcoal, peralite, sand and a small amount of soil. I throw a worm or two in my 5 gal clothe bags.

  • wgreg347

    this is a learning thing.have fun . figuring out what is wrong with a plant is all part of it. in a year or two we can look back and see what a dummy we were. this learning never stops. its challenging. rewarding.FUN.

  • gnarly dude

    Bloom Yellow Bottle , Humboldt Nutrients, Technaflora, Roots Organics, Humboldts Secret are all great lines with good results.

    Do not support Scotts Miracle Grow General Hydroponics and Botanicare and Vermicrop

  • Geo

    Dominion Organics, you will NOT regret trying these!

  • Glenn Edwards

    what about Miracle Grow?

  • Tigergamma1500

    im new to growing anything someone help pls i have auto seeds, miracle grow, and jiffy pots what do i do to get started and what else do i need