The Most Popular Fertilizers for Growing Cannabis [2023 Guide]

Without the right fertilizers and nutrients, there is virtually zero hope of obtaining a high yield cannabis crop with fat buds.

Sadly, however, many seasoned growers don’t have a great grasp of the nute transitioning that is required to optimize bud production. Increased legalization and access to DIY cultivation has led to a boom in the marijuana fertilizer market, but making sense of the hundreds of different types of products out there can be overwhelmingly difficult, to say the least.

To achieve an abundance of fat, healthy, THC-rich flower in your crop, you’ve basically got two options: A) use a cannabis-specific organic nutrient kit, or B) build your own nute profile using inert soil and a combination of organic soil amenders.

In this article, I’m going to tell you how to do both.

Let’s Be Honest: Nute Analysis is a Pain

To be perfectly honest, optimizing nutes to produce smokeable flower at the end of a grow isn’t all that simple – especially for beginners. In order to do it right, you’ve got to stay on top of your plants every day and invest in digital input/output measuring devices, which are costly and tricky to use.

Plus, to really understand what’s going on with NPK ratios in your crop, you have to extract soil samples almost daily, dissolve them into an aqueous solution, then use a soil test kit and pH meter to quantify and compare nutrient ratios.  Do you have the time to do this every day?

If you’re like 99% of average at-home DIY growers, the answer is no.

Every good grower has their preferred method of managing nute input, but my honest recommendation for new growers looking to simplify nutes during each stage of the grow cycle is to use an NPK amendment kit. You won’t develop hardcore soil analysis skills, but you’ll give yourself the best shot possible at obtaining a healthy, smokeable yield of resin-filled flower.

The Best Marijuana Fertilizer Kit (Well… At Least My Personal Favorite)

There are a few good amendment kits out there, but I started using Homegrown Cannabis Co’s Powerup kits back in May 2022 and I’ll never use another marijuana fertilizer as long as I’m growing weed at home – seriously. As long as you start with a good, unamended organic soil (like Promix HP) all you have to do is follow the instructions on the kit, and you’ll have optimal NPK ratios at each stage of your crop, from germination all the way to harvest.

I’ll explain a bit later in more detail why I’m such a fan of the Powerup kits (specifically the Advanced Marijuana Fertilizer Kit with Germ Genie), but basically they wipe out even having to think about NPKs during your grow.

You literally just dissolve the nute packs in pH-balanced water when you water the plants (I prefer wet-to-dry cycling), and that’s it. There’s no manual amendment, no pH-up/pH-down nonsense, and most importantly, no wasted crops.

If you want to take a manual approach and develop real soil amendment skills without even using cannabis fertilizer, I explain in the second half of the article how to do that.

Or, if you want to take the easiest route possible and virtually guarantee smokeable buds at the end of your cycle, visit the link below and click on “Nutrients” at the top of the page to check out Homegrown’s Powerup Packs:

Powerup Packs: Virtually a Guarantee for Smokeable Buds

Most marijuana fertilizer kits are expensive and hard for beginners to use. Homegrown Cannabis Co.’s Powerup kits honestly couldn’t be easier. They come with step-by-step instructions that explain how to add nutes to your soil, and how much to add based on the size pots you’re using. They treat up to 7 plants and they transition NPK ratios during each cycle of the grow – from taproot to final harvest.

Why I Think Powerups Are the Best Marijuana Fertilizer By Far

For most growers, soil, grow media, and nutrients are aspects of cultivation that end up becoming grossly overcomplicated. Soil is always the cheapest and easiest option for novices, and a good inert soil provides growers with complete control over the nutes their plants will receive at each stage of the growth cycle.

Starting with inert soil can also help you gain the ability to assess things like soil pH, nutrient levels, and other things, as well as urge you to learn how to read and comprehend your plants. Promix HP is my personal favorite soil; it’s an excellent inert peat moss-based soil with mycorrhizae and is easily acquired online or found at most legit gardening supply stores.

Inert soil means you’ll need to modify your nute ratios as your plants mature and grow, which will require modifying how “hot” your soil is. NPK, which stands for nitrogen, phosphorus, and potassium, are the three essential elements for growing cannabis. These are referred to as macronutrients because they are added to soil in significant amounts. In short, young plants in the veg stage need more nitrogen and less phosphorus to promote growth. (I cover nutrient loading in much more detail in other articles, but basically, less nitrogen and more potassium is needed as plants reach maturity and begin to produce budding sites).

So why are Homegrown’s Plant Powerups better than even the best marijuana fertilizers on the market? Well, in my opinion it’s because they offer the most straightforward nutrient solutions and they’re the easiest to read and understand. They’re available in two varieties (Standard and Organic), and they specify on the label which pack you should add to your soil depending on which stage of the growth cycle your plants are in.

The Organic packs, which are slightly more expensive, contain natural fertilizers made from biological sources like animal and vegetable, whereas the Standard packs contain chemical fertilizers. If you can afford to spend the extra money, I’ll always recommend using the Organic packs, because in addition to being healthier for the environment, they also release nutrients slowly into the soil for gradual absorption. This hugely lowers the possibility of issues like nutrient burn.

Some of my Other Favorite Cannabis Fertilizers

Of course, there are a plethora of other choices available when choosing nutrition mixtures for your cannabis plants. The liquid Vegamatrix blends from renowned producer Kyle Kushman is another excellent range of goods, but these are more expensive than Homegrown’s Powerups, and, in my opinion, they’re far more difficult for a novice to understand. Powerup kits come with easy-to-follow directions that explain how to add nutrients to your soil, and how much to add based on the size of the pot you’re using, among other things.

Of course, you can use additional soil amendments to supplement development at crucial points of the grow cycle, as your growing abilities and confidence increase. There is nothing simpler for a beginner, though, than the Powerup marijuana fertilizer kits, and I’ll stand by that statement until I find something better to use for my own personal grows.

Making Your Own Marijuana Fertilizer

If you’re a purist (nothing at all wrong with that), this section of the article details how you can make your own soil amendment from organic waste and compost, without even having to use or buy a marijuana fertilizer.

Vermiculite, Perlite, & Human Urine

Vermiculite and perlite are often considered interchangeable, but they are different entities. They are both relatively sterile, inorganic products, but they look and behave differently. Perlite is hard and porous, and it is made by heating volcanic glass to an extremely high temperature. Meanwhile, vermiculite is soft and spongy and made by heating mica (silicate) to an incredibly high temperature.

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

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.

Though it may sound bizarre, human urine is a fantastic fertilizer for marijuana. Fresh urine is high in nitrogen, a key nutrient in weed growth. The breakdown of your urine can depend on your diet.

When eating the typical ‘Western’ diet, the nitrogen, phosphorus, and potassium (NPK) ratio is 11-1-2. For reference, blood meal is 12-2-1.

It must be said: do not urinate directly on your plants. It will probably kill them. Urine contains a lot of salt, so it must be diluted to a ratio of at least one-part urine, and ten parts water. However, if you are watering potted plants or seedlings, dilute the urine to a 1:20 ratio.

It should go without saying that you can only use your urine if you are healthy. Do not use it if you are on medication or you have a urinary tract infection.

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 and Fish Meal

If human urine grosses you out, then bat guano is another one you might want to miss. 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 vegetative stage. Meanwhile, chicken manure releases nutrients slowly and can enhance yield.

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 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.

Composting

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.

composting

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.

Hydroponics and Carbon Dioxide Boosting

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.

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, but 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.

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