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Which Cannabis Fertilizers Should You Use?

Updated September 13, 2022

When you put in a great deal of time and effort to grow cannabis, you want to make sure that it thrives. Fertilizer is a great way to ensure that cannabis gets all of the nutrients it needs, but you need to know which one to go with. There are thousands of fertilizers on the market, and you do not need to use one that is specific to marijuana to see results. Many of the same fertilizers you would use on other garden plants will also do well with cannabis.

Explore some of the more popular fertilizers for cannabis on the market, as well as everything else you need to know about fertilizer.

Choosing Between Homemade and Store-bought Fertilizer

The first decision to make is whether you want to make your fertilizer or buy one that was formulated by professionals.


You can sometimes save money by choosing to make your fertilizer, but this is not always the case. It may be more expensive to get the required ingredients or nutrients in smaller quantities than to buy fertilizer. That changes if you make larger quantities of fertilizer, which will almost always be more affordable than buying.


If you are new to growing cannabis and growing plants in general, then you are unlikely to get as good of results with homemade fertilizer as you would with the one you buy. You do not have the knowledge needed to craft the perfect fertilizer and know what goes into it. This means that even if you save money on making it yourself, homemade fertilizer may have a lower value if it does not produce as strong of results.

By contrast, fertilizers that you buy were formulated by professionals who know the specific nutrients that cannabis needs. As such, they will include all of the essentials and should have almost guaranteed results. Of course, as you develop experience with growing cannabis, you may gain the skills to craft your fertilizer with similar effects.


It should go without saying that buying fertilizer is more convenient than making your own. If you are short on time, then it is the way to go.


Advanced growers who want to customize their fertilizer to meet the needs of their specific strains and growing conditions may want to make their fertilizer. It is much easier to customize your fertilizer than it is to find a pre-made one that meets specific requirements.

Nutrients to Look for in Fertilizers

Whether you buy fertilizer for cannabis or decide to make your own, there are some essential nutrients to look for.

Nitrogen, Phosphorus, and Potassium

Any of the cannabis fertilizers you buy should contain nitrogen, phosphorus, and potassium, abbreviated as N, P, and K, respectively. In many cases, the fertilizer will display information about their values, all as one referring to them as NPK.

Nitrogen is essential for the growth of leaves, and phosphorus helps with the growth of buds.

The potting soil that you buy for cannabis will already have NPK in it, but the levels of the nutrients found there will only be enough for as long as three weeks.

As soon as you notice leaves developing on your plant, go ahead and make sure it gets a 20 percent balance of NPK. In the case of outdoor growing, you can use the full dose, although you still may want to dilute it. For indoor growing, you should dilute it, so the formula is at half or a quarter strength. If you use too much on indoor cannabis, the leaves may droop from shock.

Remember That Fertilizers Need Water

No matter the type of fertilizer you choose to use on your cannabis plants, make sure that you water your plants appropriately. Fertilizer is useless without watering, assuming that you grow in soil. You do not want to water your plants too frequently or too infrequently.

If you are growing your marijuana in soil, ensure that the top inch of the soil feels dry, mix the nutrients into your water, and flush with pure water every other week. You should also try to let around 20 percent extra water drain out the bottom whenever you water the plants.

Soil Mixtures as Fertilizers

For those who are growing marijuana in soil, you can also adjust your soil to include the proper nutrients as a way to eliminate the need for separate fertilizers.

Perlite or Vermiculite

Try adding perlite or vermiculite to the soil, or choose a fertilizer product that has these. For soil, start with around 30 percent perlite or vermiculite. For hydroponics, start with about 50 percent in a mixture of peat moss and water.

Perlite and vermiculite are a simple way to get professional-quality soil. This comes from the fact that they are made from proportional heating of mica to between 1,400 and 1,800 degrees Fahrenheit. As they get heated, the minerals will get bigger and become porous, turning into white pellets that retain air. Those pellets are vital because they can hold nearly four times their weight in water. This is how many of the potting soils you buy will not be lumpy or dry when they are wet.

Additionally, the minerals in these pellets naturally include potassium, calcium, and magnesium, which infuse in the soil eventually. That infusion happens slowly, continuously providing the soil with nutrients.

There are so many choices of cannabis fertilizers on the market that you do not necessarily need to buy one on this list. However, if you are overwhelmed, you can stick to one of the following choices, all of which are popular among growers for good reasons.

Bergman’s Plant Food

Bergman’s Plant Food was designed to have the ideal mixture of NPK, and it is straightforward to use. There are different fertilizers in the Bergman’s Plant Food line for various stages of plant development, including seedlings, vegetative growth, and the flowering stage.

Canna Coco A + B or Cal-Mag

For those growing in coco coir, Canna Coco A + B and Canna Cal-Mag are both excellent choices. This company is among the first nutrient suppliers to specialize in cannabis, and it comes from Amsterdam.


Dyna-Gro is famous for its affordability and simplicity when it comes to growing marijuana, particularly appealing to beginners. The Grow and Bloom fertilizers are designed for the vegetative and flowering growth stages, respectively, and include simple instructions. It works with cannabis grown in soil, hydroponics, or coco coir.

Fox Farms Trio

Fox Farms is another popular option, especially for those who are new to growing marijuana. The fertilizers include all of the additives you need, and there are choices for hydroponic and soil-based growing, or it can work with coco coir. Once again, there are separate products for each stage of growth, called Grow Big, Tiger Bloom, and Big Bloom.

Future Harvest

Future Harvest is a nutrient company that has been focused on creating products for cannabis growers for two decades. The Holland Secret 3-part fertilizer is particularly helpful, as you can use it at any stage of growth and with any growth medium. The line includes three bottles, so there is something for each stage of growth.

General Hydroponics Flora Products

The Flora products from General Hydroponics are commonly used for hydroponics, coco coir, and soil growing. If you are not sure where to start, go with the performance pack that has the essential solutions and a pH balance test kit.

If you want fewer items, you can use the FloraDuo set, which has you starting with a formula high in nitrogen before moving on to one high in potassium and phosphorus.

NOT Miracle-Gro

There is some mild debate in cannabis growing circles regarding whether to use Miracle-Gro. This is easily among the best-known fertilizers, and while it does well for typical garden plants, it is not suitable for marijuana. The balance simply is not appropriate for cannabis.

Specifically, Miracle-Gro has too much nitrogen for when the cannabis is in its flowering stage. Additionally, using Miracle-Gro will only give you a single product for the entire growing cycle. It may be okay at first, but cannabis plants shift their growing requirements as they mature. For example, you need to change formulas when the plants start producing buds, as the formula you used for seedlings will no longer be ideal.

Some Homemade and Organic Fertilizers to Consider

If you prefer to make your fertilizer or want to keep things simple with a straightforward organic option, there are also several choices. These work to varying degrees and some are easier to access than others, depending on where you live.

Chicken Manure

Although it does not smell great, chicken manure is the right choice of fertilizer for cannabis. Organic manure compost will slowly release nutrients, encouraging healthy plants.


Those who want a natural solution for their cannabis fertilizer may wish to choose compost. This is an excellent option that is highly affordable and greatly enriches the soil. Ideally, you will turn the compost with a pitchfork or something similar every day. This will help convert the decay into the dirt. Your compost will probably need about three months to become fertile soil.

Human Urine

It may seem incredibly odd, but human urine can be a healthy fertilizer for growing cannabis. This comes from the high quantities of nitrogen in the urine. This mineral is crucial for the development and growth of the plants.

If you want to use this method, combine a full bladder of urine with commercial plant food in a gallon of water. Use the solution right away, because if you wait, toxic ammonia may develop.

Wood Ashes

Wood ashes are an excellent choice if you live somewhere with soil that is too acidic to grow healthy marijuana. For this method to work, grab a shovelful of some wood ashes and combine them with five gallons of water before using that water on the soil. An alternative to wood ashes is lime, which you should be able to find at garden stores.

Consider Increased CO2 as an Alternative

Yet another option is to boost the air quality via increased CO2 instead of focusing on using fertilizers. Remember that plants breathe carbon dioxide in, which leads to the plant doing very well if the grow space is abundant in CO2.

Vinegar and Baking Soda

You can combine vinegar and baking soda (carefully) to make your CO2 generator. Put some baking soda in a bowl that holds a liter. Add in some white vinegar, a drop every few minutes. The two will interact until the baking soda expands, or you no longer have vinegar. Set this bottle up as a drip by hanging the bottle over an open container or bowl halfway filled with baking soda. If you poke a small hole in the bottle cap on the vinegar, it will slowly drip out at the right speed.

Watch the Root pH to See If Fertilizer Is Necessary

In some cases, you may not even need fertilizer to encourage your cannabis plants to grow. Regularly check the pH of the roots as well as that of the water that you use. After a bit of practice, it should take five minutes or less to measure the pH. Remember that if you are growing in soil, you want a pH of 5.8 to 6.5, and if you are growing in hydroponics, it should be 5.5 to 6.5.

Most cannabis will only need fertilizer during its growth if problems occur or you notice a nutrient deficiency.

You Can Choose When to Stop Fertilizing

You should not worry too much about when to stop fertilizing your marijuana plants. You should keep using fertilizer for at least the first several weeks of flowering, but some people will stop after this. Other people will use fertilizer right up to harvest. You may want to stop using fertilizer a few weeks before harvest so you can flush the plants.

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