Cannabis & Hemp

The Best and Most Popular Cannabis Fertilizers

The type of fertilizer you choose to use for your plants can make a world of a difference in whether or not your marijuana will prosper or just be barely making it. Producing a healthy, flourishing plant requires top notch nourishment with the right ingredients.

You will want to know exactly what your plant will need for the duration of its life cycle. What your plant needs in its beginning stages will be different from what is required later. How you get your fertilizer is up to you. You have the choice of going to a local garden center or if you are feeling adventurous you can make your own. Either way knowledge is key to making the best decision.

Homemade vs. Professional

You can always make your own nutrients with your own preferred mixture, but it is usually much simpler to buy nutrients pre-made for all your marijuana plant needs. Keep in mind that marijuana plants have a wide assortment of needs.

Professional systems can prevent you from making any unforeseen mistakes with chemical reactions that may happen if you accidentally mix the nutrients the wrong way. You also won’t have to worry about deciding what to feed your plant and the necessary ratios. They already have all of that taken care of, which is especially helpful for beginners. Most likely you will save more time, money and effort by investing in a good professional nutrient system.

The first thing you need to contemplate when deciding on the proper system to buy for growing marijuana is, what do you want your growing medium to be? It is best to stay clear of any fertilizers that advertise being “slow release” or “extended”. While these systems may be good for regular plants, they are most likely going to cause an array of issues when growing marijuana.

Once you decide how you want to grow your plant, whether in soil, coco coir or hydroponics, make sure to buy products that are good for the specific process. Some products are good for growing in more than one medium and some are good only for a specific medium. 

Soil Fertilizers

Fertilizers aside, without a proper watering technique, your plants will never thrive in soil. New marijuana growers often make the mistake of watering their plants far too often.

How to Water Plants in Soil

  • At least the first top inch of the soil should feel dry.
  • You really only need to add nutrients to the water about every other watering.
  • There needs to be about 20% additional water drain at the bottom of your pot when you water them.
  • Repeat the first step.

Be sure you are always adding the proper amount of nutrients, and that you have chosen the right fertilizer for you.

Fertilizing Plants Growing in Soil

Healthy marijuana plants require three elements for firm roots and vibrant flowers with high yields. Phosphorus, potassium and nitrogen are all necessary. Nitrogen is important for enhancing the generation of leaves and phosphorus aids in bud growth. Potting soils are already mixed with these three elements which will aid the plant for up to three weeks. But as the plants grow they will need additional nutrients.

When your plants start the leafing process, you will need to give them a 20 percent balance of phosphorus, potassium and nitrogen. If you are growing indoors, you’ll want to dilute this formula to one-quarter or one-half strength. When marijuana plants are grown indoors, they do not handle full strength dosages well and it could cause the leaves to drop due to shock.

You can feed the plants each time you water, although it isn’t completely necessary. Twice per week will usually suffice. However, outdoor plants naturally get fresh air and their roots have free range to spread out and grow.

Perlite and Vermiculite Marijuana Fertilizers

It you choose hydroponic growing, either perlite or vermiculite is added in a combination of about 50 percent fertilizer and a mixture of water and peat moss. Perlite and Vermiculite are commercial fertilizers produced when mica is heated proportionately to 1,400 and 1,800 degrees Fahrenheit. When heated the minerals will enlarge, becoming porous. This creates white pellets retain air, have the ability to take in almost four times their own weight in water and will make sure solid potting soils never become tough lumps when dry.

The minerals in this formula naturally create magnesium, calcium and potassium that will eventually become infused into the soil feeding it with nutrients. After some time the pellets of both fertilizers become immersed in a mixture of the minerals discharged into the soil.

Urine as a Marijuana Fertilizer

So, we already know that nitrogen is necessary for marijuana growth and development. Well, human urine contains large amounts of nitrogen. Your urine is a healthy fertilizer for marijuana!

Now you don’t want to just go and urinate directly on the plants or even on the ground around it, as this could kill them. Instead mix a commercial plant food with one full bladder’s worth of urine per each gallon of water. You will have to use this solution immediately to avoid any toxic ammonia from formulating.

Chicken Manure

Chicken manure makes a nice marijuana fertilizer too. Organic slow release chicken manure compost increases yields and promotes healthy plants.

Wood Ashes

Let’s say you live in an area where the soil is highly acidic, even too much for happy marijuana growing, you can use plain wood ashes to nullify the acids. Just mix a shovelful of wood ashes per 5-gallon bucket of water to the soil. And if that is not an option you can also try getting lime from a garden center in your area to do the same thing.

Vinegar-Baking Soda CO2 Generator

Plants breathe in carbon dioxide and exhale oxygen, so naturally marijuana flourishes in surroundings that are high in carbon dioxide (CO2). White vinegar is an excellent source for creating carbon dioxide. You can do this by taking a 1-liter bowl with baking soda in it and slowly dripping white vinegar into a 1-liter bowl. One drop of white vinegar every two minutes will suffice. When the vinegar mixes with the baking soda a chemical response occurs that makes the two substances inactive, creating ample carbon dioxide. This takes place until either the baking soda is nullified or the vinegar is completely gone.

Indoor grower can use vinegar generators the same way I.V. drips are used in the hospital. The easiest way to do it is take a bottle that is filled with vinegar, duct-tape and hang it over some sort of open bowl or container that is filled half way with baking soda. Poke a hole in the vinegar bottle cap with a small finishing nail which allows it to drip its contents from the hole and mix into the baking soda in the bowl underneath it.

CO2 Bomb

 The best environment for a vinegar/baking soda drip generator is in a small confined space where there is no air that will blow away any of the CO2. You also definitely do not want the smell of vinegar that could bring unwanted attention to your marijuana growing operation.

A vinegar-soda drip generator doesn’t work well an outdoor setting; where open breezes quickly carry off any CO2 that is generated. A steady and unmistakable odor of vinegar, if the breeze was favorable, could also lead thieves or authorities directly to your plot.

For this process to be effective you want to create a carbon dioxide filled environment that totally stops any of the CO2 from going out of the space. You can even completely cover your plant with a huge plastic bag long enough to touch the ground and still not bend over the top of the plant.

After that, put some sort of open plastic jar or container with 1-quarter baking soda standing up right under the huge plastic bag you are using to cover the plant. Next, from underneath the hem of the bag, pour a tablespoon of vinegar into the open jar. Pour just enough that it starts to foam as it creates CO2. Then go ahead and place the bag back on the ground.

Give it about 15 minutes before adding additional vinegar to the rest of the baking soda. Be sure to make sure everything is blending very well by mixing the contents with a stick. The CO2 bag needs to remain on the plant for at least four hours so everything is completely submerged in the tissues. You can repeat these steps as you feel it needs to be done. There is no such thing as giving your marijuana plant too much CO2. When doing these bombs most people prefer to do it at night time due to the smell it creates.


Compost isn’t necessarily the first form of fertilizer that most people would think of and let’s face it this doesn’t bring about the most pleasant thoughts either. Truth is that animal manure and left over food from your kitchen, creates some bountiful, thriving marijuana crops.

Animal manure and vegetables/fruits are recycled back into the earth the same as any other organic thing would, and along with it goes all the nutrients contained within it. These nutrients will be absorbed by your plant. Using compost as fertilizer can be done in any location. If you are in an area where the soil is lacking what is needed to produce a good crop, then this will enrich the soil.

After your first pile of compost is created and in the process of decomposing, you can start building another one. Use a pitchfork to turn the compost to make sure everything is blended really well. Do this frequently, preferably daily to reduce the amount of time it takes to transform from a state of decay to dirt.

Another important reason to do this daily is to avoid spontaneous combustion. This is the last thing you want. Spontaneous combustion happens when heat created by microbes feeding on rotting material that is under some form of pressure dries, then catches fire, burning the substances that it generated from. Be aware that certain foods will decay much faster in hot temperatures. Also, give your compost about three full months to transition into rich soil.

Hydroponics Fertilizers

Some people prefer to grow their marijuana with the roots planted in water. This is called growing your plant hydroponically. Using this method, there are no loose particles and it will never stop up your pumps, tube and any other hydroponic equipment you may own.

Coco Fertilizers

Growing in coco coir, or coconut coir, can have similar advantages to growing in a hydroponics system. Coir is the fiber that comes from the coconut husk, and it’s used in a variety of products as well as for gardeners. Any foods you use to grow in hydroponics can also be grown in coco coir.

Make sure to keep the pH between 5.5 – 6.5 and give it regular water every other time you water. Also take into account that extra calcium and magnesium will need to be added. It is quite common for coco coir to experience calcium and magnesium deficiencies so having this supplement is a must. It doesn’t matter which one you get. Most are fairly inexpensive and will work perfectly.

Root pH

Effectively managing the pH of your root is vital to protecting plants from nutrient problems. Before you water marijuana plants check the pH of the water. For marijuana to properly absorb the nutrients it receives, the pH has to be right.

There are some pH test kits available at a decent price that will do this for you. Some of the nutrient systems on the market even provide these kits. After you have done this a few times, it will only take you about 5 minutes, and it can be done when you water your plants. You want to do this to ensure the plants are in the best health at all times. Don’t worry about always getting the pH right. It is far more vital that it is monitored to see that is remains between the proper ranges. The proper pH range for soil growth is 5.8 – 6.5 and the proper pH range for hydroponics growth is 5.5 – 6.5.

When to Stop Fertilizing

There isn’t one definitive answer to this question. It really depends on the grower as everyone has a preferred way of doing things. You may choose to either fertilize until the harvest time, or you can refrain from fertilizing days or even weeks prior to the end.

Generally, you would no longer provide nutrients to soil grown plants earlier than plants grown in hydroponics. A time of 1-14 days or more flush is common for hydroponic growers. It is best to nourish your plants with nutrients for flowering and blooming for the first few weeks or longer of this process. You can choose to start flushing your plants about two weeks prior to harvest time. Be sure to use good judgment of when you think your plants are ready to be flushed.

Unless there are deficiencies such as the yellowing of leaves around the base of the plant, then you really do not need to give your plant a ton of nutrients. The way the plant tastes is affected by how much nutrients are added to it, so overdoing it could cause the taste to be off.

Whatever the suggested amount of nutrients is, it is best to cut that amount in half in the beginning and increase the dosage as soon as you detect the first sign of malnourishment problems, if any occur. Remember that a small amount really does go quite far!

Increase Nutrient Levels

Seeing yellow leaves near the base of the plant is fine so long as it is closer to the end of the flowering stage. Yellow leaves only need to be addressed in the early stages of the marijuana plants life cycle. Just be certain to make sure there are enough leaves to make it to harvest time.

Overfeeding a plant can cause nutrient burns which will never go away. Once the damage is done there is nothing you can do about it. Literally all the leaves will be burned forever. Nutrient burn is a sure sign you have done too much. If in fact the buds are already developing, overfeeding may lead to burns on the sugar leaves on the plant buds. Although the actual buds may be fine, this results in the harvested buds looking very rough.

Starting the dosage at half strength is best unless deficiencies are present. All strands are created different and you just may have a strand that can easily be affected by nutrient burn. Usually, the only people who have to increase their nutrients are the ones with fast growing plants and are using bright lights.

If marijuana is being grown hydroponically, you can investigate the PPM (Parts Per Million) of the water, to observe exactly what your plants need. If you choose to water the plants by hand, then monitor the PPM of the run-off water at the bottom as well as the water you are powering into it.  By observing the run-off water after the nutrients were poured in, it is easier to notice if there is a difference in the PPM. Let’s say you notice the PPM increases then it is an indicator that you may be providing more than enough nutrients. However, if the PPM decreases, then it necessary give your plant more food since your plant is absorbing the nutrients to the point that it is not leaving additional food.

Background information for this story was provided by Robert Bergman from

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