Where to Find Fertilizer for Growing Marijuana

Every plant has different requirements to grow to the best version it can, and marijuana is no different. Left on their own, cannabis plants will grow just fine. But you’re not looking for fine, you want healthy buds and a plentiful harvest to make the most of your growing efforts.
How can you make sure you’re getting the most from your plants and growing the best buds possible? You can feed them a specific fertilizer for growing marijuana. Fertilizer is just a fancy name for the essential nutrients plants need to survive and grow. It’s an essential component to getting the best flower production and highest yields from your plants, but when it comes to cannabis fertilizers it can be difficult to know where to start.
If you’re new to growing, or even if you’re not, in this post we’ll cover all things fertilizer – from what it is to what you need to know about fertilizer for growing marijuana. After all, the right nutrients at the right time will not only optimize the health of your crop, it’ll help optimize your yield too.

outdoor cannabis fertilizer
Review of Reefertilizer® Bloom Flowering Nutrients for Cannabis by Anonymous

What is cannabis fertilizer?

In simple terms, fertilizers are food for plants and supply the essential nutrients that help plants grow and thrive.  These nutrients are essential for plant growth and a balanced source of nutrients helps support plant growth in different stages.  Different growth stages call for different levels of nutrients and understanding the basics of fertilizer can help you make the right decision for your plants.  Cannabis requires plenty of nutrition to produce high yields and a fertilizer designed specifically for cannabis is the best way to make sure your plants are getting what they need and when they need it.

When it comes to feeding your plants, not all fertilizers are created equal.  Plants need both micro and macro nutrients, in different quantities, to fully grow and function.  Macronutrients are those needed in large amounts and make up the foundation of fertilizers.  The main macronutrients all plants need are nitrogen (N), phosphorus (P), and potassium (K) and cannabis is no different.  Plants demand heavy quantities of these essential elements depending on where they are in their growth stage.  Each nutrient contributes to plant growth in a different way and you’ll see the ratios of each listed on fertilizer packages as NPK or a series of 3 numbers (separated by dashes).  These numbers represent the percent of nitrogen, phosphorus, and potassium by weight found in the package.  Balanced or complete fertilizers will have equal amounts of each but the right fertilizer for your needs will depend on the circumstances.

Micronutrients are those used in smaller amounts and include boron, chlorine, copper, iron, manganese, molybdenum, nickel, zinc, magnesium, and calcium.  Although marijuana needs smaller amounts of these nutrients, they are essential to plant growth and their absence or deficiency can have negative consequences for your plants.  Calcium and magnesium are especially important as essential secondary micronutrients and the right mix will have your plants growing to their full potential.

Understanding what nutrients to use, and at which stage are invaluable to your growing success.  Even though they are needed in smaller amounts, nutrients like calcium and magnesium are key for proper plant development and any deficiencies can significantly impact your grow.  How much of these key nutrients you will need to supplement with, if at all, depends greatly on your growing substrate.

What nutrients are in soil

Basic potting soil will contain enough nutrients to feed your cannabis plants for at least two weeks.  They are a growing medium that will contain enough nitrogen, phosphorus, and potassium, as well as other trace minerals needed for healthy plants.  But after two weeks, you’ll need to start feeding plants additional nutrients.  Various amendments can be added to your soil to replenish nutrients or adjust the mixture, based on your needs.  Adding compost to your soil will lower your requirements for additional fertilizers, or you can use a soil conditioner like Reefertilizer Start to get the most benefits early on in the plant’s growth cycle and help your plants establish a strong root zone.

If you use another medium, like coco coir, you will need to add fertilizer right from the start.  Coco coir is a substrate made from processed, recycled fiber from coconut husks and as a soilless medium it contains no nutrients or minerals.  Growing in this inert medium can provide great yields, but because it doesn’t contain any nutrients you’ll need to feed your plant more often and keep a closer eye on nutrient levels.

Where to find cannabis nutrients

Now that you know more about fertilizer for growing marijuana, you also need to know where to find it.  Garden centers can be a great starting point since they focus on growing all sorts of plants.  They usually have a great selection of soil and soil amendments, and can offer lots of helpful advice.  They may not be as versed in growing cannabis though so doing your research and having a general idea of what you need can go a long way.

Hydroponic stores can be a great source for finding fertilizer for growing marijuana whether you have a hydroponic setup or not.  Although they specialize in growing indoors (usually hydroponically), they also support more traditional growing as well.  Most staff and store owners are experts in their field and these stores can be more cannabis focused than traditional stores since it’s a popular growing method for marijuana.  Even though you can get up close and personal with the products, the options are often overwhelming.  Rely on staff at your local store to steer you in the right direction as they are often happy to help you learn the ins and outs of cannabis nutrient requirements and have practical knowledge of the products for sale.  You’ll get the benefit of talking to a passionate grower who has hands-on experience and can even suggest solutions you may not have considered.

You may not have a local store or even a garden center to rely on though, but your plants still need their nutrients.  Online options abound but it can be hard to choose with so many alternatives.  Amazon is always a solid choice to see what is available and honest reviews can help you pick out what you need and see what’s worked for others.  Online stores like Reefertilzer offer both education and fertilizer for growing marijuana along with a variety of accessories, shipped right to your door. Speciality sites like this one can be a goldmine for learning how to care for your plants and you can usually score free shipping on larger orders.

Review of Reefertilizer® Grow and Bloom Cannabis Nutrients
Review of Step by Step Growing System - Start + Grow + Bloom by Carolyn P.

How to feed your plants cannabis fertilizer

Your plant’s nutrient requirements will change depending on which stage of growth it’s in.  Seedlings get a small stockpile of nutrients from the seed and water is absorbed through the leaves until the root system develops.  At about 3-4 weeks old, or when the plant has 3 to 4 sets of leaves it has entered the vegetative growth phase and you can start using fertilizer.

Plants should be fed once or twice a week, but many fertilizers for growing marijuana come with a feed chart that can help you determine what nutrients you need during the different stages and when to feed them.  You can use PPM measurements to make sure your plants are getting the nutrients they need and the information can help you correct nutrient levels or avoid over or under feeding your cannabis.

How often you feed your plants depends on numerous factors of your grow setup though so be ready to adjust accordingly. Plants use most of their energy during the day and will absorb water more readily in light or during the heat of the day.  Feeding just before dawn or first thing in the morning is the most suitable time.   

Best Nutrients for cannabis Seedlings

The first set of leaves you see on a cannabis seedling are called cotyledons and they carry enough nutrients to sustain the plant in this stage.  As they open they will start collecting energy through photosynthesis while the root system begins to develop and spread.  Using an organic compost packed with beneficial microbes provides a better environment to metabolize nutrients and water.  A few scoops of an organic soil conditioner like Reefertilizer Start can help build your living soil and promote strong and healthy root growth.  Designed for young seedlings and clones, it gives the most benefits early on in the plant’s growth cycle.  A small dose of organic nutrients can help speed up root growth and get your plants off to the right start.

Best Nutrients for marijuana plants in vegetative stage

Marijuana plants in the vegetative stage need lots of nitrogen to stay healthy and strong.  In terms of NPK ratios, look for fertilizers with a higher nitrogen number to promote green foliage and stemdevelopment.  Once the plant has 3-4 sets of leaves you can use a fertilizer specifically designed for this stage of growth.  Along with micro-nutrients important to the growth phase, a fertilizer for growing marijuana like Reefertilizer Grow can help prevent nutrient deficiencies and keep your plants thriving during this stage of growth.

Best Nutrients for weed plants in flower

As your plants enter the flowering stage, the fertilizer you use and the NPK ratio will change.  Plants in the flowering stage of growth need a fertilizer high in phosphorus and potassium (the P and K in the NPK ratio).  During this stage, your plants will be using nutrients to build flowers and buds, and a fertilizer that also contains calcium can help the process.  A nutrient blend designed for this stage, like Reefertilizer Bloom, will promote dense bud growth and terpene production.  Calcium and magnesium are important nutrients for flowering buds and by introducing them you’ll encourage the growth of strong and healthy buds.  Reefertilizer Bloom has nutrients designed for mature plants and will help your plants realize their full flowering potential by including the necessary macro and micronutrients to build flowers and buds.

Review of Reefertilizer® Grow & Bloom Nutrients for Veg & Flower by Marty


The right nutrients in the right combination, and at the right time, are essential for optimal growth. Finding the right fertilizer for growing marijuana can be overwhelming but it doesn’t have to be.  If you get the balance right and give your plants the attention they need, you’ll be rewarded with tasty and healthy buds. Using a system specifically designed for your plants’ changing needs can make all the difference.  Ultimately the right choice for you will be the fertilizer for growing marijuana that fits your budget and needs, not to mention level of involvement.  Reefertilizer has a range of cannabis fertilizers and nutrients designed to target your nutritional needs at every stage of growth.

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