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How to Use Nutrients and Fertilizers to Grow Marijuana

Nutrients and Fertilizers

There are three things a plant needs for survival: adequate sunlight, soil, and water.

If the conditions are met, your plant can grow and develop. However, if you want to grow your marijuana plant and maximize the quality and quantity of your harvest then you need the right nutrients and fertilizers.

Although soil has several nutrients, you may need additional nutrients to support the plants’ growing needs.

So what are these nutrients? How can they help your cannabis plants to grow and produce healthy yields? Let’s find out.


How to Fertilize Your Plants?

Even though many of us want to start cannabis breeding, we have no idea about fertilizers and nutrients that help the plant thrive.

Plants need different cannabis nutrients for their various growth stages.

There are three main ways to fertilize your cannabis plant.

  • Liquid Nutrients: You can mix these with water and other additives and water the soil. The plants will absorb the nutrients through their root.
  • Powdered Nutrients: These can be mixed in soil with other additives or sprinkled onto the soil.
  • Nutrient Spray: Another way to ensure your plant gets the cannabis nutrients is by diluting spray from liquid fertilizers and additives. Simply mix it with water and spray it over the plant.



What are Cannabis Nutrients?

Cannabis plants require a lot more nutrients and fertilizer than other plants.

Now the kind of fertilizer you need also depends on your yield and where you intend to grow the crop.


For Outdoor Growing Cannabis Plants

If you are planning to grow cannabis plants outside, the best time and way to add nutrients is while transplanting the weed plant. Just add powdered nutrients to the soil so the plant can derive all the nutrients it needs for all its stages of growth.

You can later add more plant nutrients to the soil as required.


For Plants Growing Indoors

Liquid Nutrients mixed with water are the best way to nourish indoor cannabis plants.

However, the task is complex. It requires accurate measurements and regular watering.


Types of Nutrients – NPK Fertilizers

You’ll often find fertilizers marked as NPK or read about NPK fertilizers while learning about healthy plant nutrition and growth. NPK are acronyms for three important nutrients, i.e., nitrogen, phosphorus, and potassium.

Plants need these fertilizers to grow.


Fertilizers for Different Stages

Each stage of the plant’s lifecycle requires a different set of nutrients. Most cannabis fertilizers come labeled for each stage, and the nutrients needed by the marijuana plants are also listed therein.

These fertilizers have NPK as the essential components, but the quantity and composition vary per the requirements for each stage.

For instance, you’ll need more nitrogen for the vegetative stage. At the same time, your plants will need low amounts of phosphorus and potassium at the initial stage.

Then for the flowering stage, fertilizers will have more phosphorus and low amounts of nitrogen and potassium. These are also called bloom nutrients.

However, the concentration varies for each fertilizer. Hence it’s very important to read the labels and ensure you buy the right products for your plant and their nutrient requirements for each stage.

Moreover, there are marked instructions about the use of each fertilizer too. Make sure to go through them and follow them. Some fertilizers have to be fed all through the life of the crop.

At the same time, specific fertilizers for each stage should be stopped when the plants have transitioned to the next stage.


What Nutrients Does a Cannabis Plant Need?

In broad terms, two categories of nutrients aid plant growth.

Macronutrients and micronutrients.

NPK constitutes the macronutrients. Whereas calcium, sulfur, and magnesium are the micronutrients. Then there’s another class of lesser-known micronutrients like:

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


Your cannabis plant needs a combination of these nutrients to grow. Micronutrients are required in smaller amounts but are very important. They aid in the metabolic functioning of the plant.

Macronutrients are also the primary nutrients. Micronutrients are secondary nutrients.

Micronutrients are derived from air, water, and soil. Let’s look at these nutrients in detail and see what they do for the cannabis plant.



Nitrogen is a much-needed ingredient, especially during vegetative growth. Plants need it to convert sunlight to energy.

Also, it’s part of amino acids, a major constituent of proteins in the plant. These make the plant sturdy and healthy.

A plant with nitrogen deficiency will have stunted growth.

Another benefit of nitrogen is that it makes nucleic acid of RNA and DNA.



Phosphorus mainly works in the flowering stage and helps the plant grow large and strong buds.

Phosphorus aids nutrient absorption in the plant, facilitating growth and building a strong base.

Plants with phosphorus nutrient deficiency may wilt and cannot develop flowers.



Potassium plays several roles in the development of plants. It works as a regulatory nutrient. It helps keep the plant growing and in osmoregulation.

Osmoregulation is the process of water and salt regulation in the plant. There are tiny pores on the leaves called stomata. Potassium helps open and close them to retain and exchange water, oxygen, and carbon dioxide.

It also helps in storing energy released by the plant during photosynthesis.

In photosynthesis, the plant breaks down sunlight energy and uses it to produce glucose. This glucose serves as a food or energy source for the plant to meet its growth needs.

If a plant doesn’t meet its potassium requirements, it wilts and looks burnt and dead.



Calcium is important for optimal growth of the plant. If the plant doesn’t get enough calcium, the leaves will curl up and develop brown marks.



Another important micronutrient is magnesium. It is the main component of chlorophyll and helps the plant metabolize glucose.

The absence of magnesium causes the leaves to turn yellow and discolored.


How Many Nutrients Do Cannabis Plants Need?

The amount of nutrients your cannabis plant needs depends on many factors, including:

  • The size of the flower pot
  • The state of the growing medium
  • Condition of the root system
  • Other environmental factors


cannabis nutrients


How to Use and Mix Nutrients

Usually, the cannabis fertilizer bags and nutrients will have labeled quantities of the macronutrients. These labelings will be written something like this: N-P-K: 10-5-5

This means the product has 10% nitrogen and 5% phosphorus and potassium. Different brands will have different nutrient ratios.

You can also look for fertilizers simply labeled as grow or flowering nutrients. However, generic fertilizers, also called all-purpose fertilizers, may work for your lawn and a few other plants, but it’s a big no for cannabis plants.

During the last stages, right before harvesting the yield, you need to flush the plants. During this stage, you should only give the plants water so it clears any remaining nutrient residue in the buds.


Using Liquid Nutrients

Usually, you’ll see people using liquid nutrients for hydroponics, weed plants, and grow media.

Liquid Nutrients are best for indoor plants but can also be given to those growing outdoors. You can give your plants these nutrients via hoses, drip lines, and misters.

To make the solution use a large water tank and determine the quantity of water you need for your plants. Then add the required ratio of the nutrients to the water as per the directions on the fertilizer pack.


Build Your Schedule

The best way to ensure you water your plants per their requirements and provide them with the much-needed nutrients timely is to make a feeding schedule.

It will help you know when to water the plants and how much nutrients you need to feed them. You can also chart out a plan for the level of nutrients you need with the watering and how often you need to provide them.

However, these liquid fertilizers are fast acting, so be careful not to overfeed the plants. In fact, as a rule of thumb, use them alternatively with each watering.

You may also try starting with a slightly lower than the recommended dose and then upping it to the optimal levels. But remember, underfeeding and overfeeding will have disastrous effects on your crop.


How to Read Fertilizer Numbers

Learning what the numbers and percentages on the fertilizer packs mean will take time. But you’ll get the hang of it.

For now, the most important numbers to note are the percentages of the macronutrients. These percentages will vary for each product and brand, but the balance will be around the same for each stage.


Organic vs. Synthetic Fertilizers?

Fertilizers may be derived from natural or unnatural sources. Synthetic fertilizers come from inorganic waste matter, minerals, and atmospheric gasses.

On the other hand, organic fertilizers are derived from organic waste and microbes.


Organic Fertilizers

Fertilizers that come from organic sources are beneficial for both the organic soil as well as the plant. They are naturally occurring and hence do not harm or damage the plants.

They stimulate growth and facilitate the beneficial microorganisms. The soil microbes help convert the fertilizer into easily absorbable plant nutrients.

Organic fertilizers also contain many of the secondary nutrients that aid plant growth. On the downside, they have a low NPK nutrient ratio. But they can help the plant thrive for a longer time.

Also, the results are slow, but your plant stays green and lives longer when fed organic nutrients.


Synthetic Fertilizers

Synthetic fertilizers act fast and are available in a variety of forms. You can find powders, liquids, pellets, spikes, and even granules.

They easily dissolve in water and provide a quick feed to your crop with all the needed nutrients in their optimal quantities. However, you must regularly feed your plants to keep them thriving and green.

So although the synthetic nutrients work well for the plants, they don’t do much for the soil.

Moreover, you have to watch the quantity you feed your crop. Too many nutrients can damage the crop and cause nutrient burn or toxicity.   


Check Your Water pH Levels.

Use a pH meter or a pH testing kit to check the pH level of the water for nutrients. Ideally, it should be between 5.8 – 6.2.


Importance of Timing and Frequency When Using Nutrients and Fertilizers

This is very important since adding nutrients to water every time you water the plants could lead to nutrient lockout or overfeeding.

Plants need just only water feedings in between the fertilizer feeding too. Again, your schedule will guide you on when you should add nutrients to the water.

In broad terms, it is best to add them on every second water feed, ensuring you feed the plants twice every 7-10 days.

Also, keep tabs on the health of your plant. Yellowing or wilting should be concerning and indicate either overfeeding or underfeeding.

Always stay at the optimal or recommended levels for feeding the crop. Malnourished leaves and stems will wilt and will not produce flowering buds.


When to Fertilize Cannabis Plants

The right time for fertilizing plants depends on their lifecycle stage.

They’ll need more nutrients during certain stages (like the veg stage). In contrast, there may be periods when you should hold off the fertilizer, like the time right before the harvest.

As for the vegetative phase, wait for your plant to grow out the roots a bit, then start feeding the fertilizer.

Another sign that indicates the right time to start feeding the plant is when it starts growing leaves, or the leaves get three points. Then begin slowly and gently bring up the dose to the recommended levels.

Notice the color of your plant; yellow indicates paleness or deficient plant. An extremely dark green color means the plant is getting too much fertilizer. The optimal way to feed should be by adding fertilizer in every second watering cycle.

Once you spot a bud or flower on the plant, it indicates it has entered the flowering stage. You need to switch to flowering or bloom fertilizer now.


Can You Fertilize Seedlings or Clones?

It’s not recommended to provide fertilizers or nutrients to seeds and clones. These are the very initial stages of the plant’s lifecycle. Only water them regularly at this stage and let them grow.


Fertilizing When Rooting – Root Stimulants

Once the plant sprouts roots, you should use a root stimulant to improve health and foster plant growth. This is usually during the second or third week following planting the seeds.

These stimulants provide the plant with nutrients and phytohormones, which help in root growth.

Keep notes about the plant growth as you start adding these nutrients. Start with a low dose and increase it to the recommended level within the first three weeks.


Nutrients for Marijuana Plant in the Vegetative Stage

Nitrogen plays a very important role during the veg or growth stage. It helps the plant grow leaves, stems and branch out.

This is also when the plant extends its roots and forms new ones. So if we leave the plant to natural soil, it won’t be able to suffice its needs for NPK nutrients. Many plants start losing color at this stage due to the deficiency.

So depending on the condition of your plant and the growth fertilizer instructions, start with a low dosage. If you notice the plant needs more nutrients, increase the dosage gradually.

Plants at the growing stage absorb nutrients much faster because of their growing needs. So make it a regular practice to feed them the optimal dose.

But in any case, never exceed the recommended dosage, as it may cause further deterioration. Always keep track of the growth and monitor any retardation.

In case of overfeeding or nutrient toxicity, flush them out. Use three liters of water for every liter of the substrate and water the plants. This will drain the excessive salts and minerals.

This stage lasts between four to twelve weeks.


Nutrients for Marijuana in the Flowering Stage

The leaves, branches, and stems have already grown during the flowering stage. Now the plant develops buds and flowers.

It needs phosphorus and potassium as the primary ‘bloom’ nutrients. However, under or over-feeding at this stage can directly affect your yield.

Start from the second week and feed the plants a minimum dosage and bring it to optimal levels slowly. As they start maturing, stop the feed and occasionally flush them out.

Moreover, at times it’s hard to know what might be affecting the yield. The plants may have access to adequate nutrients but may be unable to absorb them due to non-facilitating factors like low pH levels.

That’s why we need adequate monitoring of the pH and EC levels at this stage.

Using biostimulants or enzymes once a week can help keep the balance. You can also use micronutrients like calcium, phosphorus, magnesium, potassium, etc., around the end of the flowering stage to make up for the deficiencies, if any.

Remember, the better you feed your plant at this stage, the better will be the outcome or yield will be.


Fertilizing Mature plants

Stop feeding the plants fertilizer over the last few weeks before the harvest. This way, the flowering buds will have more of a natural aroma and flavor.

The plant doesn’t need any extra nutrients at this stage, anyway. The flowers and bugs are only maturing; all the developmental phases are complete.

So what you can do for your plants is flush them out twice a week or in ten days.


Organic Fertilizers for Marijuana Plants

Organic fertilizers are derived from natural sources like animal or vegetable waste, gypsum, glacial rock dust, etc.

The fertilizer contains several minerals and nutrients for the plants. Organic fertilizers are best for outdoor plants and can be sprinkled over the soil in powdered form or mixed with other additives during the plantation.

The best thing about these fertilizers is that you don’t have to add nutrients throughout the life of the plants. All you have to do is water the soil; the nutrients are already there, so the plant will absorb them as needed.

Organic nutrients sources include:


For Nitrogen

  • Worm castings
  • Bat guano
  • Fish meal


For Phosphorus

  • Rock dust
  • Bone meal


For Potassium

  • Kelp meal
  • Wood ash


Cannabis Fertilizer


Applying Compost Tea to Cannabis

Compost is full of essential organic nutrients important for cannabis plant growth.

The process of steeping compost in aerated water is called making or brewing compost tea. It is a way to remove microorganisms and other nutrients from a water or tea solution.

Thereon you can add these important nutrients and beneficial bacteria into the soil of cannabis plants. All these nutrients work together to keep the plants safe, protected, and aid their growth and development.

Compost tea can be considered a supplement or complementary addition to other important nutrients.

There are two ways to introduce compost tea to your weed yield. You can either apply it to the soil or make a spray and spray it all over the leaves.


Applying Compost to the Soil

Compost tea can be applied to the roots via the soil or sprayed over the leaves.

To apply, dilute the blend with water, and use it in a ratio of 1:20 when you apply it to the roots. Whereas for the spray, keep the mixture at a ratio of 1:2.

However, avoid the urge to feed your plants’ compost tea via drip lines.

Since it’s a heavy mix, it can easily block out your pipes. The best way is to use the diaphragm pump dedicated to the purpose.

Compost application to the soil aids healthy roots and protects the plant from diseases and stunted growth.

In the process, microorganisms having all the nutrients are added to the soil. These aerate the soil and increase the plant’s ability to absorb nutrients. It also helps the weed plants to retain more water.


Composition of Compost Tea

A healthy composition of compost tea includes fungi, bacteria, and protozoa with all the required soluble nutrients for the healthy growth of the cannabis plant.

The major ingredients that make-up compost tea are:


  1. Compost

Of course, the first element should be a healthy mix of compost. That should contain local pathogenic microorganisms and nutrients.


  1. Worm Castings

Worm castings are digestive byproducts produced by worms. These have many nutrients and microorganisms available in a broken-down form and are easily absorbed by plants.


  1. Fish Hydrolysate

These are the remnants of fish and other crustaceans.

The skeletons of crustaceans have an important element, chitin, which helps boost the immunity of weed plants.


  1. Kelp

Kelp is food for fungi. It helps form fungal colonies essential to the compost tea and supports plant growth.


  1. Molasses

Molasses aid bacterial growth and serve as food for them.


Steps to Make Compost Tea

Here are DIY steps to make compost tea on your own at home.


Step 1: Make a Compost Tea Brewer

Take large buckets (about 5 gallons capacity), an air pump, and an aerator device.

Connect the aeration with the air pump. These will help oxygenate water to help the microorganisms in the compost thrive.

Get some tea brewers or a mesh bag to keep all the ingredients needed to make the compost tea.


Step 2: Work out a Schedule

This kind of tea will take time to cook. So you need to figure out the right time for applying the compost tea and coincide it with when you intend to brew it.

It will take you 2-3 days to brew the compost tea. But don’t go over the timeline, or you may kill all the much-needed microorganisms.

So always get brewing when you need to apply the tea within 2-3 days. Then as soon as it’s ready, take a spray bottle and spray it over the leaves during day time.

You may also opt for the morning or evening times when the temperature is right and the direct sun doesn’t hit the plants.

During these times, the stomata (tiny pores on the leaves) are also open and can easily absorb nutrients.


Step 3: Make Your Compost Tea Bag

Use clean water for the batch and ensure the pump works and your compost tea is not under direct sunlight.


Step 4: Finish Your Compost Tea Blend

You can add several products to your compost tea during brewing or when you finish.

For instance, you may add food for fungi or bacteria to aid their growth. This way, your plants will get a healthier blend and active good bacteria and fungi.


Tips for Growing a Better Yield of Cannabis Plants

Here are a few tips and tricks to help you feed your plants right and ensure you get the healthiest and largest yield on your crop.

  • Use natural chelates to increase the absorption ability of your plants.
  • Make sure your grow room setup has adequate ventilation. Plants will get the needed oxygen and carbon from the air.
  • Foliar spraying is an effective way to take care of any nutrient deficiencies in the plant.
  • Flushing is very important. During the last few weeks, flush out often so there’s no remaining taste or smell of the fertilizers in the buds and flowers of your yield.
  • You may use tap water for watering the plants; else, bottled water can do the job quite as well.
  • If the water isn’t clean, use carbon-based on other filters that’ll remove the chlorine and other harmful elements from the water.


Wrapping Up with Nutrients and Fertilizers for Weed

It’s hard work taking care of cannabis plants. Too much fertilizer can burn them out, while too little can cause deficiencies.

With this article as your guide, you can easily see what fertilizers you need for all the stages of the plant’s lifecycle. Also, be mindful of the dose, how, and when to feed the plant.

With these precautions, you can rest assured you will get a large amount of quality yield, which is the ultimate objective of successful cannabis growers.

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