fertilizer for weed

The Most Popular Fertilizers for Growing Cannabis [Guide]

With an increase in the number of states where people are legally allowed to grow marijuana, it was inevitable that the fertilizer market would take off. Without the right fertilizers and nutrients , there is no hope of your weed producing fat buds. While you need to be careful not to overdo it and cause nutrient burn, a lack of fertilizer will ultimately harm your plant.

In this guide, we look at the best fertilizers and provide a quick guide on making your own.

Vermiculite and Perlite

While these materials are often considered to be interchangeable, they are different entities. They are both relatively sterile inorganic products but look and act differently. Perlite is hard and porous and is made by heating volcanic glass to an extremely high temperature. Vermiculite is soft and spongy and made by heating mica to an incredibly high temperature.

Perlite is normally white, traps water, and has a slightly alkaline pH. Vermiculite is tan or brown, absorbs water, and has an almost neutral pH. The two materials are often sold together despite their differences, and the combination absorbs water up to four times its weight.

These materials are ideal for preventing your soil from hardening when it dries.

Most importantly perhaps, vermiculite and perlite provide calcium, magnesium, and potassium, which gets into the soil and nourishes your marijuana. If you have a hydroponics setup , you can create a fertilizer that includes 50% of perlite and vermiculite, with the rest made up of peat moss and water. If you are using soil, you only need 10% of perlite and vermiculite in your fertilizer.

Human Urine

As bizarre as it sounds, your urine is a fantastic fertilizer for your marijuana plants. Fresh human urine is high in nitrogen, one of the key nutrients in weed growth . The breakdown of your urine depends on your diet. If you follow a ‘Western’ diet, the nitrogen, phosphorus, potassium (NPK) ratio is 11-1-2. For reference, blood meal is 12-2-1.

As urine contains a lot of salt, it must be diluted to a ratio of at least one-part urine, 10 parts water. DO NOT URINATE DIRECTLY ON THE PLANTS! It will probably kill them. If you plan to use your wee on potted plants or seedlings, dilute the urine to a 1:20 ratio in water.

It should go without saying that you must only use your urine if you are healthy. Don’t use it if you are on medication or have a urinary tract infection. By the way, if you are grossed out by the thought of using urine, how do you feel about bat guano or cow poop?

Wood Ashes

Yet another unexpected fertilizer, wood ash contains ample potassium and lime for your plants. Believe it or not, you can even use the ashes from your fireplace, assuming you have burned wood. You can lightly scatter the ashes on your plants, or add them to a compost heap. One issue is that the ash will produce high amounts of salt and lye if it gets wet.

It is also important to note that ashes from hardwood trees, such as maple and oak, contain more nutrients than ash from other trees, on average. Wood ash also acts as an effective pesticide by keeping slugs, snails, and other soft-bodied invertebrates at bay.

Bat Guano

A fancy term for bat poo, guano has been used as a soil enricher for eons. You can also use manure from other animals including chickens and cows. Bat guano is often worked into the soil or made into compost tea. Bat guano’s NPK ratio is 10-3-1 which means it is high in nitrogen and ideal for use in your weed’s vegetative stage . Chicken manure releases nutrients slowly and can enhance yield.

Fish Meal

Fish meal is typically made from ground-up parts of the fish that are inedible. The result is a fine powder that can be added to your soil. Fish emulsion is pressed fish oil. When combined with the meal, it prolongs the release of the nutrients. Fish meal is high in nitrogen. Alternatives include blood, bone, and soy meal.

Worm Castings

This is what comes out of an earthworm once it digests soil or other organic components. It is laden with tiny organisms and loaded with nutrients. It is commonly added to compost tea because adding it directly to weed, especially during the flowering stage, could result in your marijuana tasting like worm feces.


Experienced gardeners know that organic material will ultimately grow back into the soil , and take with it the nutrients in the original matter. You could compost kitchen waste and other organic materials and expect to be rewarded with wonderfully fertile soil. As well as boosting your plant’s growth, composting reduces your landfill contribution and enriches the soil in your locality.

Your compost heap can contain anything; as long as it is organic.

This means the food you throw out, chicken manure, worm castings, and bone meal. After you have created your compost heap, turn the compost with a pitchfork (daily if possible) until the contents have been properly mixed. By doing this, you maximize decomposition and reduce the time it takes for the heap to become usable. As a rule of thumb, you can expect it to take three months for your compost to become usable.

You can also create a compost tea, which is basically a liquid version of your compost heap. You need organic molasses, organic compost, water, a bucket, and a few other materials. It normally takes around three days to make, and you should use it as soon as possible.


If you have a hydroponics setup, it means you are using a growing medium such as Rockwool or coco coir instead of soil. As a result, you need store-bought nutrients made especially for hydroponics. These nutrients will contain no organic matter as they are provided through minerals, and should contain optimum NPK ratios.

With marijuana, you need high nitrogen, medium phosphorus, and high potassium during the vegetative stage. During the flowering stage, you need high phosphorus and potassium, and low nitrogen. What you buy must also contain various micronutrients such as iron, copper, boron, sulfur, manganese, and magnesium.

Carbon Dioxide Boosting

The process of photosynthesis involves plants using oxygen, sunlight, and carbon dioxide (CO2) to create energy. When you increase the CO2 in your grow room , you boost your marijuana plants’ growth. One of the simplest ways to achieve this is by using white vinegar and baking soda. Set it up so that one drop of vinegar falls into a bowl of baking soda every two minutes, and marvel at the CO2 increase in the room.

In an outdoor setting, you need to improvise as the smell of vinegar could land you in trouble with the authorities. A useful CO2 increasing technique involves placing a large plastic bag over the plant. Then, fill an empty plastic jar with baking soda until it is 25% full. Put the open jar beneath the tent created by the plastic bag.

Pour a tablespoon of vinegar into the jar until it begins to foam, a sign that it is generating CO2. Reseal the bag, allow the plant to breathe for a quarter of an hour and add more vinegar to what’s left of the baking soda. Stir with a stick and leave the bag over the plant for at least four hours.

If you are growing indoors, you could invest in a CO2 cylinder or a generator.

Synthetic or Organic Fertilizer?

There are tried and trusted products such as Miracle-Gro that are worth buying if you are a novice grower. Over time, however, you will learn that pre-packaged products are expensive and wasteful, not to mention bad for the environment. Once you learn how to create your own organic fertilizer, there’s a danger you will get addicted!

As well as saving a small fortune, you learn so much more about plant nutrition, and gain an understanding of what your plants need, and when . Eventually, this knowledge will lead to larger yields and more potent buds. The key is to determine what nutrients each organic element brings. For example:

  • Nitrogen: Worm castings, bat guano, human urine, and chicken manure.
  • Phosphorus: Bone and fish meals, rock dust, and banana peels.
  • Potassium: Fish meal, wood ash, and kelp.
  • Calcium: Clay, gypsum, and limestone.
  • Magnesium: Epsom salts and dolomite.

When Should I Stop Fertilizing?

Make sure you create a feed chart to discover what happens when you feed specific nutrients to your plants at set growth stages. If the leaves of your marijuana plants are turning yellow or look burnt long before harvest, it could be a case of nitrogen burn. Check your feed chart to see if it is a likely reason.

If your plants are being overfed, perform a flush with pH neutral water, but don’t do it in the week before forcing the plants into flowering.

Keep an eye out for deficiencies but resist the urge to add extra fertilizer. Marijuana plants often need fewer nutrients than you think. Perform a flush any time from two weeks away from harvest, or else your weed could taste of fertilizer!

Final Thoughts on Marijuana Fertilizers

If you see yellow leaves near the base of your plants as harvest time approaches, there’s no need to panic as that’s a normal occurrence. It is all too easy to overfeed your plants and cause nutrient burn, an issue that could damage your plant permanently, at least in an aesthetic sense.

If you are using a store-bought fertilizer, begin with half of the recommended dose unless there are clear signs of nutrient deficiency. The amount of nutrients your plant needs depends on the marijuana strain. When using organic fertilizer, start small and gradually increase the dose as and when it is needed.

Although you can use ready-made fertilizers as a novice, it is best to educate yourself on the topic and learn how to create organic fertilizers. Not only will it be better for the soil, and the environment in the long-term, it also helps you gain valuable insight into the world of gardening. The more knowledge you possess, the more likely it is that you will grow bigger plants and enjoy greater yields .

Our detailed guide to some of the best fertilizers available for your marijuana garden, including how to make your own organic blends.

5 Best Fertilizers For Growing Cannabis

It’s true that cannabis plants really do grow like a weed, but in order to thrive, marijuana plants need nutrients. Also referred to as fertilizers, these are utilized by growers to give plants the essential nutrients they need. Using the right fertilizers when growing cannabis can help plants flourish, significantly increasing their health and ensuring optimal yields come harvest.

Before We Get To The Top 5: Why You Should Use Cannabis Fertilizers

If you’re growing weed, it’s safe to say you want to grow the best weed you can. Growing healthy, high-yielding cannabis plants comes down to ensuring that they get the nutrients they need to thrive. Cannabis fertilizers can help tremendously with this.

For plants to grow as healthy as they possibly can, they need these three major nutrients: nitrogen (N), phosphorous (P) and potassium (K). These are usually found on marijuana fertilizer labeling displayed in a numerical sequence that corresponds to the amount of N-P-K the fertilizer contains.

Let’s break down what each nutrient does to get a better understanding of what the benefits of using weed fertilizer really are.

  • Nitrogen (N): Nitrogen is considered the most important nutrient aiding in plant growth. This is because it’s a major component of chlorophyll, which is vital for the process of photosynthesis. Nitrogen is also an important component of amino acids, which are the building blocks of proteins that plants need to survive. You, as a grower, want to feed cannabis more Nitrogen during the vegetative stage, when it uptakes the most growth.
  • Phosphorous (P): Phosphorus is an essential component of a plant’s DNA and RNA structure, which are linked together by phosphorous bonds. Phosphorous is known to increase root development and stalk and stem strength, improve bud formation and overall crop quality, and help aid in the plant’s development throughout its entire lifecycle. The intake of Phosphorous should be increased during the flowering stage.
  • Potassium (K): Potassium also plays a big role in photosynthesis and is vital for both the development and overall health of the plant. Potassium and phosphorous work together to increase the root system’s strength and resistance. Potassium is also essential for growing big, heavy buds, and can help increase the overall weight and density of cannabis flowers. That’s why, along with Phosphorous, your plant’s diet during the flowering stage needs to include lots of Potassium.

Thus, it’s easy to see why using fertilizer is so beneficial for growing healthy marijuana plants heavy with dense, beautiful buds. Without any additional nutrients, your plants will most likely starve and struggle to produce that quality and quantity of the harvest you’re hoping for.

High Yielding Strains

The Top 5 Cannabis Fertilizers For Growing Great Weed

Using the best nutrients for growing weed can help ensure that you’re growing the best weed you can. This is typically the goal of any grower, whether they’ve been growing weed for years or are cultivating cannabis for the very first time.

Giving your marijuana plants the best food you possibly can throughout each stage of their life will aid in healthy root development, robust growth and dense, heavy buds.

Marijuana fertilizers can be separated into two different types: organic and synthetic. Like other fertilizers, you’ll find them available in both liquid and powder form. There are also fertilizers in pellet form. The following are some of the very best nutrients for growing weed that will significantly help your ganja garden grow.

  1. FoxFarm Liquid Nutrient Trio

FoxFarm is a popular and is an excellent choice for beginner growers. Not only is FoxFarm extremely easy to use, but it also contains everything you’ll need for your grow to flourish. FoxFarm’s Liquid Nutrient Trio is available in both soil and hydroponic varieties, so it’s important to make sure you’re getting the right one for whatever growing medium you choose to use. It can be used in coco coir grows as well.

FoxFarm Liquid Nutrient Trio comes with three different bottles available in a package deal: Big Bloom, Grow Big and Tiger Bloom. They’re designed to work together through the plant’s life cycle to support hearty growth (Grow Big), multiple blooms (Big Bloom) and an abundance of buds (Tiger Bloom).

  1. General Hydroponics Flora Grow Bloom Micro Combo

If you’re interested in the best fertilizer for cannabis, check out General Hydroponics Flora Grow Bloom Micro Combo. This top selling trio is designed to be used in hydroponic, soil and coco coir grows. Nutrients come pH balanced, are easy to use, and make a great choice for both newbies and experienced growers.

The Flora Series uses a building block approach, with each bottle containing the primary, secondary and micronutrients that plants need to flourish. Each mixture can be adjusted for the individual needs of your plants throughout each stage of the growing cycle. Flora Grow supports vigorous plant growth during veg, Flora Micro helps with plant growth and flower blooms, and Flora Micro is designed to be used during flowering for improved yields and big, dense buds.

  1. Advanced Nutrients Bloom, Micro, and Grow

Advanced Nutrients Bloom, Micro, & Grow combo is another option for some of the soil, hydroponic or coco coir grows. This trio contains all you need to grow a lush, dense cannabis garden no matter what growing medium you choose.

Each individual one-liter bottle of this is perfectly formulated to give your plants the right ratio of nutrients throughout every stage of their growth. Grow is used to enhance plant growth during the vegetative stage, Micro helps to boost plant growth and increased flower production, and Bloom is designed for producing gorgeous, dense buds.

Each formulation is perfectly pH balanced and designed to adjust pH levels for you, eliminating the need to worry over pH levels during your plant’s lifecycle. Advanced Nutrients also contains a unique chelation that allows more nutrients to reach your plant’s roots, ensuring the healthiest plants possible.

  1. Biobizz Bio Grow, Bio Bloom, Top Max

Biobizz has been creating plant nutrients for almost 30 years, and their Bio Grow, Bio Bloom, and Top Max triple combo is a top-selling fertilizer for marijuana plants in soil or substrate mixtures. Both new and experienced cannabis growers will appreciate these certified organic nutrients designed for healthy plants and abundant harvests. A complete nutrient schedule is available for download on the Biobizz website, taking the guesswork out of how much and how often plants should be fed.

Bio Grow is a complete that can be used throughout all stages of plant growth, including both veg and flower periods. Once plants begin to flower, growers will benefit from Bio Bloom, an impeccable mix of nitrogen, potassium, phosphorous, amino acids and enzymes that result in big, potent buds. Top Max works in harmony with Bio Bloom and is designed to be used during the entire flowering period. Using Top Max increases flower size and weight, produces better-tasting buds, and results in more nutrient uptake.

  1. Botanicare CNS17 Grow / CNS17 Bloom

Botanicare CNS17 Grow and Bloom formulas are a cost-effective solution when looking for the best marijuana nutrients. These highly concentrated formulas come in one-gallon containers, with a price point that’s perfect for budget-minded growers looking for high yields at a low cost.

CNS17 Grow is among the best marijuana nutrientsdesigned to be used during the vegetative stage, resulting in bigger and healthier plants by supporting root development, decreased internodal spacing and stronger, sturdier branches with its ideal nitrogen to potassium ratio. Once plants move into their flowering stage, CNS17 Bloom formula should be introduced to obtain maximum fruiting and flowering. With perfect phosphorous and potassium levels, combined with trace minerals, calcium and sulfates, CNS17 Bloom is perfect for boosting the size of your buds and increasing overall yields come harvest.

Should You Always Use Cannabis Fertilizer?

Given how important fertilizer can be for the health of your plants, is it always necessary to use it?

Honestly, it all depends on the growing medium you’re using.

Some soils come pre-amended with the nutrients your plants need to thrive throughout their lifecycle. If your soil doesn’t have nutrients added to it, you’ll need to use the best marijuana fertilizer you can if you want to grow the best plants you possibly can.

Growing weed hydroponically and in substrate mixtures like coco coir and rockwool will always require fertilizer because plants aren’t getting any nutrients from the soil. Using marijuana fertilizer replaces any nutrients that soil naturally contains, allowing plants to establish healthy roots and grow into strong, healthy plants that produce a bounty of buds.

Next, we’ll take a more in-depth look at using marijuana fertilizer in different types of growing mediums.

Using Cannabis Fertilizer For Growing Weed In Soil

If you’re using soil to grow your plants, it’s not always necessary to use fertilizer to grow quality cannabis, especially if you grow smaller autoflowering varieties. There are several types of soil that come already enriched with the nutrients cannabis needs and therefore require less added fertilization. These ready-to-grow soil types contain a complex assortment of amendments that can make it possible to go without feeding your cannabis plants at all.

Using soil that hasn’t been amended is a bit different, and you’ll need to use a cannabis fertilizer to ensure plants grow healthy and strong. Loam soil (a mixture of clay, sand and silt) is one of the most ideal soils for growing cannabis, as it drains well, has good water retention, retains nutrients, has an almost neutral pH level and contains high oxygen levels. However, it has little to no nutrients on its own, so it will need to be additionally enriched.

Growing in soil requires using the correct fertilizer for various stages of marijuana plant growth. For example, different fertilizers will be needed for seedlings, vegetative growth, and the flowering period respectively. Seedlings can also be fed cannabis fertilizer intended for vegetative growth, but keep in mind that you should use only a quarter of the amount recommended for mature plants.

Using Cannabis Nutrients For Hydroponics

No soil means no nutrients. Seeing that plants are grown without soil in hydroponic setups, these types of grows will always require fertilizer. In hydroponic grows, cannabis fertilizer replaces nutrients that soil would typically provide. When done right, hydroponic setups are known for producing great weed because plants are given perfectly measured servings of the nutrients they need to thrive.

When growing weed in hydroponic setups, you’ll need to use marijuana plant food that’s designed specifically for hydroponic grows – for the best results, aim for the best hydroponic fertilizer for cannabis – check our top 5 again for fool-proof options.

Some fertilizers can be used in soil and hydroponic setups, while others are designed specifically for hydro grows. If you plan on growing hydroponically, make sure you get a fertilizer that you’re sure is compatible with a hydroponic system.

When choosing the best nutrients for growing weed, be sure to always look for the NPK ratio on the nutrient label. In hydroponic marijuana fertilizers, the minerals added to your fertilizer should also be chelated, which means they’re protected by an organic molecule that makes them less sensitive to pH changes. This allows for a wider pH range and proper nutrient absorption.

Cannabis Seeds For Hydroponics

Using Fertilizers For Other Soil-Less Media Used To Grow Marijuana

Growing cannabis isn’t just limited to soil and hydroponic systems. Other alternatives to growing weed include soil-less media like rockwool and coco coir.

Rockwool has been a staple in successful cannabis setups for years. This soft, wool-like substance is spun from basalt rock and just so happens to contain the perfect properties cannabis roots need to thrive. Rockwool is a type of hydroponic setup that will always require cannabis fertilizer, as it doesn’t contain any nutrients on its own. When the correct ratio of fertilizer is given to plants grown in rockwool, however, growers can expect huge yields come harvest.

Coco coir has become another popular alternative to growing weed in recent years, great for both indoor and outdoor grows. Made from the recycled natural fiber of coconuts, coco coir is comparable to soil that doesn’t have any nutrients added to it. It can be used on its own but is typically blended with soil because it drains better and allows more oxygen to the plant’s roots. Coco coir fertilizer is any hydroponic cannabis nutrient mix – it tends to lead to better results than the best cannabis nutrients for soil. Keep in mind that nutrient levels could need special consideration when growing in coco coir.

Indoor Cannabis Strains

Fertilizers And Nutrients For Weed Plants: The Final Word

When you need to use nutrients for your weed plants, it’s important to use the best marijuana fertilizer you possibly can. You won’t always need it, but when you do, choosing the best cannabis nutrients for soil or hydroponic setups is a crucial aspect of any cannabis grow.

If you’re new to using nutrients for growing weed, be sure to monitor your plants closely and start lower than the suggested feeding dose. You can then slowly increase the amount until you notice your plants beginning to really thrive. Using too much fertilizer can cause nutrient burn, while using too little can stunt plant growth. Knowing when to stop fertilizing weed is also important – usually, it’s a good practice to stop a couple weeks prior to harvest. However, always check producers’ recommendations for instructions.

In the end, using nutrients for growing weed is an integral part of the process that allows plants to thrive throughout each stage of their lifecycle and produce big, heavy buds of which any grower can be proud.

Picking a fertilizer for your weed is a hard task – so much of the harvest’s success relies on nutrients! Luckily, this top 5 has everything to satisfy all weed plants’ needs.