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.
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?
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.
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 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.
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.
How And Why To Create Homemade Organic Fertilizers
Organic fertilizers can save you money and boost your yields. Here’s an overview on how and why you should make your own homemade fertilizer. You won’t regret it!
It has never been easier to start growing cannabis. The sheer amount of products and options available can be overwhelming, but they are all intended to make your life easier. That does not mean new systems will be cheaper or more effective than traditional methods for tending to your plants. It really depends on the scale of your operation and your goals as a cultivator.
SYNTHETIC VS ORGANIC FERTILIZERS
There seem to be two distinct schools of thought; one involves modern, petrochemical-intensive monoculture production, where sterile conditions and precise metric manipulation of variables are intended to maximise production. Bottled nutrients with strict NPK values and a short pH-range are utilised to minimise deficiencies and support robust growth.
The other technique is the organic or “natural” way, in which plants are grown without petrochemical influence. In this scenario, what is really happening is you are feeding the soil microbiology, which in turn directly feeds the roots all of their favourite munchies in just the right proportions.
New, inexperienced growers need some time to delve into the intricacies of each method – organic vs synthetic. Analyse the pros and cons, then get going with growing! You will surely change your mind on numerous subjects as you develop your green thumb.
ARE BOTTLED PRODUCTS WORTH IT?
As time passes, you will soon start to notice that most of what you buy in a bottle is either exceedingly expensive, wasted, or easily substituted at a fraction of the price with your own concoctions.
Take into consideration that most bottled fertilizers, be they synthetic or organic, lose some of their price value due to the high water content contained within. It is also extremely complicated to mix everything a plant needs into a stabilised bottle. There are limits to chemistry and plant physiology. Nutritional performance is surely lost to bottled convenience.
MAKING YOUR OWN FERTILIZER
Making you own fertilizer can get quite addictive. Not only will you save a significant amount of money in the long-run, you will also begin to understand plant nutrition to a much greater extent, learn to dial-in exactly what your plants require, and ultimately, harvest bigger and better-tasting buds.
Are you throwing away your premium-price bagged soil after each crop or heavily dosing your plants with nutrients and additives without any significant increase in yield?
If so, simply read on.
HOMEMADE FERTILIZER: WHAT DO PLANTS EAT?
We will not go too deep into this subject, rather, we shall quickly provide some basic concepts. Surely you have seen “NPK” mentioned before. These are the macronutrients – the big players in a plant’s health and development.
- N – nitrogen
- P – phosphorus
- K – potassium
Along with these macros, we also have micronutrients, referred to as trace elements. These are metals and minerals that the plant needs in very small quantities, yet are of equal importance as NPK for healthy plant growth. Examples include calcium, magnesium, copper, iron, zinc, manganese, cobalt, iodine, selenium, molybdenum.
We also include vitamins and acids here, along with other organic compounds.
Fertilizer manufacturers essentially mix these and attempt to chemically stabilise them for bottling, transportation, and shelf-life. Any given nutrient line is just that brand’s take on a full nutritional plan; all of them claim to be better than the rest.
The secret to a grade-A yield is the right proportion of these constituents at the right time. In this sense, these nutrient lines are quite convenient.
But there is simply no replacement for creating or supplementing with your own, homemade organic fertilizer. In fact, that is what the best of growers do on a regular basis. With some experimentation, you will soon understand how easy this is, and what a difference organic soil makes in your garden.
The main reason for making organic nutrients is quite simple; they can be extremely cheap (or free), and you can make them in your backyard or kitchen with household appliances. They are often very easy to make, are not dangerous, and ultimately, are more environmentally friendly.
Composting, for instance, can save you a ton of hard-earned cash. After a harvest, the soil you used needs to be “recharged”. Most indoor tent growers simply throw away the depleted soil and buy a fresh new bag. That means lugging bags in and out and buying new soil each run. If you start composting all your organic food waste along with your used soil, magic happens. The soil is literally recycled and recharged with all the necessary microbiology and high-quality food your plants need. It will contain everything – NPK, trace elements, and an army of agro-bacteria and mycos to colonise your rhizosphere.
HUNGRY HUNGRY CANNABIS
But cannabis can be a very hungry plant, and if you want those highly desired, heavy, and dense nugs, you need to supplement the base soil conditions. Since you technically do not feed your plants directly when growing in soil, we highly recommend getting into the habit of brewing your own bacteria. The technical term is Actively Aerated Compost Tea (AACT), but the slang terms “bennies”, “beneficial bacterial tea”, worm casting tea, or just compost tea are frequently used.
Regardless of terminology, they are simple to make. Prepare to be amazed. Not only will you create millions of little minions that will protect and feed your roots, you will also extract the best mineral and fungal properties of these soils into a tea, which you can directly feed to your roots, or use as a foliar spray against most common diseases.
If you are growing outdoors and/or your soil quality needs a serious boost, here are some common amendments.
If you need a nitrogen (N) boost, you can add worm castings, a chicken manure recipe, crustaceous meal, and/or bat guano. You can also use human urine, but be sure to dilute it at a ratio of 10:1 parts water to urine. Otherwise, the urine will turn to ammonia and harm your plants. Never pee directly on your plants, it will burn the roots!
If you need a phosphorous (P) boost, boil some banana peels and drench your soil. Let it ferment slightly for optimal onset. Bone and fish meals, chicken manure, and rock dust are also great sources of phosphorus. Rock dust, for instance, is a slow-release source, so it’s great to mix with your depleted soil for a crop-long source of P.
If you need a potassium (K) boost, banana peel, bat guano, fish meal, kelp, wood ash, compost, and siliceous rocks are all great sources.
The two micronutrients calcium and magnesium should be set aside, as these are particularly important, especially during bloom. Only after these reach optimum levels can the other trace elements function to their full potential.
Calcium – limestone, clay, chalk, gypsum
Magnesium – dolomite, magnesium sulfate (Epsom salts)
Other trace elements – azomite (trace nutrients and humic acid)
It is very rare to need to specifically boost other trace elements. They are present in the vast majority of soils and rocks. In fact, most of the amendments we suggested will excessively turbo-charge with trace elements, although this is not a bad thing.
Manure recipes are as old as agriculture itself. Man started to notice that where animals went to do their business, flora would flourish. Manure, to this day, continues to be one of the main agricultural inputs across the globe.
Manure recipes are a fantastic source of slow-release NPK, but they pose two medium-risk problems. If not properly composted or fermented, they can potentially present harmful pathogens to humans, animals, and plants. They can also be a bit tricky to balance with your base soil. So there is no right or wrong manure recipe choice, it depends on your region. Talk to local farmers to get a sense what works best.
- Sheep – Balanced and rich, but requires fermentation
- Goat – Similar to sheep, but stronger
- Cow – Not so rich, but easy to source and to work with
- Swine – Obsolete
- Chicken – Very rich, but usually exceedingly strong in NPK – be sure to dilute
- Rabbit – Best for composting and worm production, very rich
- Equine – Easy to work with and exceptionally great for pot flowers
TAKE IT A STEP FURTHER – GO VEGANIC!
If you are environmentally conscious, here is a quick note about “organic” fertilizers. Petrochemical fertilizers are really bad for the environment, but so are animal-derived products like bone or fish meals, among others.
First of all, the organic label is not a synonym of good, better, or correct. If you really care about the environment, be on the lookout for the OMRI certificate on bottles.
These animal by-products are industrial leftovers that are chemically treated and dehydrated to squeeze every last inch of profit possible out of the industrial process. They are far from being “organic”; they simply contain unadulterated organic raw materials before they are treated with synthetic chemicals. Way better that petrochemicals, but still, our environmental conscience and global warming efforts must not stop there.
Legendary, award-winning cannabis editor, writer, breeder, and activist Kyle Kushman is at the forefront of veganic (plant-based) cultivation of cannabis. Results are clear. If you respect millions of years of natural selection, you will be able to reach maximum genetic potential. Stop trying to cheat Mother Nature. She’s got dibs on experimentation and time.
THAT WAS WAY TOO COMPLICATED
If you are new to this, you may be suffering from information overload. How on earth could you ditch your handy bottles and get your hands dirty in cow dung?
We’re not suggesting that. In fact, we have barely scraped the surface of this subject. Entire books are dedicated to this very issue. It is tremendously difficult to condense so much information into so few words and make it pragmatically useful. We hope this is like a little seed of information to get you going in the right direction.
Above all, please understand that after you manage to get over the learning curve, it all is very simple!
BASIC HOMEMADE FERTILIZERS
To give you some perspective, you only need a bag of premium worm humus (if you are not composting yourself), a bucket, a strong pump, and an airstone; in 48h, you could breed enough aerobic bacteria, fungi, and trace minerals to make your plants go into turbo production mode. Do this every odd week during a crop cycle to net yourself a 20-40% increase in yield. It really is as simple as that.
Indoors or outdoors, you can compost your kitchen rejects like onion skins and egg shells or leftover salads; better still, use the stems and leaves from your last crop! To that, add some worms to drive your composting, and soon you will save tons on soil, recycling it into a world-class grow medium!
Don’t want to pay for kelp extract? If you live near the sea, just go out hunting for seaweeds and make your own seaweed infusion. And if you manage to do it right, it may well be more effective than the bottled version.
WORK YOUR WAY TO ORGANIC
If you are new to this, please do not feel overwhelmed with all these new terms. They are very similar, yet all slightly different. The trick is to understand your base growing medium, and what inputs you need to produce great results. Even pure hydroponics can benefit from organic additives.
We are not suggesting you ditch all commercial-grade nutrients. Rather, start supplementing those with your organic, homemade fertilizers. Baby steps.
Take it one extra level at a time. Eventually, you will notice that not only are your plants growing better, your bank account will grow too.
Little changes like adding compost teas will have a compounding effect. Your plants will grow more vigorously, and your soil will not deplete so aggressively.
Just by reading this article, you are halfway to a fully sustainable model. Feel free to experiment and adapt your methodology for a greener tomorrow.
FERMENTED PLANT JUICE (FPJ)
Fermented plant juice is a cheap and easy way to provide nutrients to your cannabis plants. This completely natural and organic method harnesses beneficial bacteria to break down plants into easily absorbed nutrients. It’s a simple way of creating super soil in your garden. FPJ is a product used commonly in Korean Natural Farming — a holistic cultivation approach that seeks to improve soil health through the use of indigenous microorganisms and the avoiding of chemicals.
Gardeners create FPJ using nutrient-dense plants and herbs such as comfrey, yarrow, stinging nettle, mugwort, aloe vera, horsetail, lambsquartres, and thistle. Some of these plants are viewed as common weeds and grow in most gardens. They’re a superb free source of plant nutrition! It’s best to harvest the young portions of these plants, which are particularly nutritionally-dense.
Some growers choose to use fruit instead of plants to create fermented fruit juice (FFJ). The concept here is the same — these natural products contain a wealth of nutrients that can be liberated by beneficial bacteria. Popular fruits include cantaloupe melons, apricots, berries, tomatoes, and sweet peppers.
Regardless of the source used, plant or fruit, bacteria are the real heroes here. These tiny beings conduct the metabolic process of fermentation. They extract energy from molecules and break down larger molecules into smaller ones. Essentially, they free up all the nutrition stored in fruits and plants.
These microorganisms feed on sugar and convert the energy source into alcohol. During this process, they create a nutrient-dense soup, which will provide your plant with many of the minerals they need for healthy growth. Sugar is also added to help pull nutrients and juices out of the plant material. This happens through the process called osmosis — the movement of solvent molecules from an area of low concentration to an area of high concentration.
HOW TO MAKE FERMENTED PLANT/FRUIT JUICE
Making your own FPJ or FFJ at home is super easy. Choose from the list of plants or fruits above and let’s get started.
Peel and cube your chosen fruit. If you’re using plants, chop them up into smaller pieces. If you’re using plants or fruits from your garden, don’t wash them! They possess beneficial bacteria that will enhance the fermentation process.
Weigh your fruit or plants before placing them into a large glass jar or a container. Add in an equal amount of brown sugar and mash up the plant material with a large spoon. Mix everything up to distribute the sugar all over the plant material.
Cover the opening of your jar or container with a piece of cheesecloth. Use an elastic band to keep it tightly attached. The small holes in the material will allow carbon dioxide created through fermentation to escape. Store the mixture in a cool and dark place for 7–14 days.
Strain the mixture through a fine sieve and pour it into bottles for storage. Keep them in the fridge until you’re ready to use them.
Add four tablespoons of mixture to about 3.5 litres of water and apply as a foliar spray or use for watering.
Did you know you can save a ton on fertilizer? We show you how with an overview of homemade organic fertilizers.