What Cannabis Fertilizer Do You Need For Growing Weed?

Cannabis being grown outdoors with fertilizer

What is Cannabis Fertilizer?

How Do You Choose the right cannabis fertilizer?

Cannabis needs light, oxygen, and fertilizer to grow. Fertilizers can be made up of many organic and inorganic elements. Depending on the stage of marijuana plant growth, a plant will require different ratios of these elements.
Growers should choose a fertilizer designed specifically for cannabis is usually the easiest and best choice. Reefertilizer Grow and Bloom are designed for the vegetative and flowering stages of cannabis.

Does Cannabis Need Fertilizer to Grow Big Buds?

To get big buds, you need the right set of nutrients during the flowering stage. Flowering cannabis plants will require plenty of potassium but less nitrogen than before. Elements such as calcium and magnesium help produce dense buds.
The difference between miracle-gro and cannabis fertilizers like Reefertilizer is that Miracle Gro was designed as a general fertilizer for many types of plants, not just marijuana. Reefertilizer Bloom is blended to the specific nutritional needs of cannabis during flower. Helping you get those big thick buds.

Reefertilizer Bloom Is Our Blend Of Major and Micronutrients Crucial to Flower and Terpene Production | Learn More

What Nutrients Does Cannabis Need to Grow?

Plants all require the same types of nutrients, but each plant will have a preference for a certain ratio depending on its current needs.
You should feed your marijuana a fertilizer that contains all major nutrients; nitrogen, potassium, and phosphorus.
There are other essential nutrients that are required in smaller amounts. Cannabis plants will get some of these lesser nutrients from compost in the soil and trace amounts in tap water. But with a full spectrum cannabis fertilizer all the major and minor nutrients will be available.

Why Did We Create Reefertilizer?

When I first started growing cannabis I was overwhelmed by all the different types of fertilizers at the garden centers and hydro shops. Hundred of liquid bottles with big promises for “60% bigger juicier buds”, complicated feeding schedules, and a price that made any mistakes very expensive. I knew it had to be simpler than all that, so I started doing research.

Cannabis isn’t much different from other edible plants in your garden like tomatoes or zucchini. The trick is giving the plant what it needs to support and maintain optimum growth. With weed, you want to build a strong root system and plant to support all the dense buds that will eventually grow.

We made a three-part system to make weed growing simpler. Reefertilizer Start for building strong and resilient root systems. Reefertilizer Grow for a strong stalk and faster growth. Then there’s Reefertilizer Bloom which helps facilitate flower growth.

But fertilizer is only one part of the puzzle. We also support our growers with personalized help and regular updates to this blog. Here you will find tips for growing good weed whether you’re an absolute beginner or seasoned cannabis grower.

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What Are The Major Nutrients (N-P-K)?

When you buy nutrients it should have 3 numbers on the front of the fertilizer’s package. These numbers represent the ratio of the three major building blocks for plant growth; Nitrogen, Phosphorus, and Potassium. This is the NPK ratio. The “N” and “P” stands for nitrogen and phosphorus, the K represents the greek name for potassium.

Nitrogen plays an important role in cannabis plant growth, it helps develop new leaves and branches during the vegetative phase. During flower nitrogen takes a much lesser role while phosphorus and potassium are needed in higher amounts to help work on bud/flower development.

What’s a Good Cannabis Fertilizer NPK Ratio I Should Look for On Packaging?

The NPK ratio numbers represent the percentage by weight of each major nutrient. During the veg phase of growth, your marijuana plants will need a higher percentage of nitrogen than potassium or phosphorus. For example, Reefertilizer Grow has an NPK ratio of 20-5-10 while bloom has a ratio of 5-30-20. During flowering, your cannabis plants need a different ratio for their new focus on growing flowers.

Why are NPK numbers higher on synthetic nutrients than organic? I answer that down below.

Marijuana fertilizers
outdoor cannabis fertilizer
cannabis fertilizer

What Are Minor and Micro-Nutrients For Cannabis?

Nitrogen, phosphorus, and potassium are 3 of the 17 essential nutrients for plant life. The others are minor nutrients or micronutrients. They are required but in a much smaller quantity.
Calcium, magnesium, iron, manganese, and copper are just a few micronutrients that cannabis will need to facilitate healthy growth.
This is why I like to grow in soil, many of these trace micronutrients are already present and available when the plants need them.

Which fertilizer works well for Cannabis?

The best nutrients for marijuana growers is the one that best meets your situation requirements.
Going fully organic and making your own compost teas and soil mixes will result in big healthy plants, but will require a lot of space, time, and experience to apply these techniques.
Using a synthetic marijuana fertilizer like Grow and Bloom makes it easier to guarantee your plants are getting what they need with very little oversight. It’s also cheaper and easier to apply.
Synthetic nutrients are sometimes called “chemical”. In some circles the word chemical has a negative stigma around it, which is silly. All nutrients are chemical in nature, water is a chemical. “Organic” nutrients are made from natural sources like potash and compost that are broken down and applied to plants. Synthetic fertilizers are further processed so they are more concentrated, they are also faster acting since they take way less time to break down than organic. Be careful with fish based nutrients, they can sometimes have high heavy metal counts.

The Reefertilizer Grow Kit Is Our Simple All-In-One Solution To Growing Great Weed | Learn More

What Are The Advantages of Using Powder Fertilizer for Marijuana?

Fertilizers will come in the form of a liquid or a powder. Both work well and the best choice depends on the grower.
Different elements will react with each other when in a liquid form causing it to lose potency over time. Because of this you will see many different variations of liquid fertilizers with different nutrient ratios. All these liquid fertilizers need to be mixed to the correct ratio for whatever phase of growth your plant is currently in to have a thriving marijuana plant.
What’s great about powder nutrients is that you don’t need to mix several products together just to feed you plant. The powdered elements won’t react with each other when dry. A few scoops of Bloom mixed into water accomplishes the same as several bottles of liquid nutrients. Powdered fertilizer saves growers time, prevents any guesswork, and utilizes far less packaging.

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Reefertilizer nutrients for cannabis Start Grow and Bloom outdoors

How Do I Use Cannabis Fertilizer?

When Do You Start Using Powder Fertilizer on Cannabis?

You’ll want to start feeding your marijuana plants with a diluted dose of fertilizer when they have developped 3 or 4 sets of leaves. Check out our blog post on “When should you start feeding your cannabis plants fertilizer”, it answers this question in more detail.
As the plant grows it will require larger amounts of fertilizer to fuel that growth.

How Much Powder Fertilizer Does A Cannabis Plant Need?

The amount of marijuana plant food your plants need depends on a few outside factors. Large marijuana plants will require more nutrients than smaller ones. The planter size is a good indicator of how big a plant will probably grow. Cannabis grown in soil can grow very tall since their roots can go deep into the ground.
You need to feed your cannabis plants enough fertilizer that the soil around the roots is completely saturated.  A small planter might need only 4L of nutrient water every feeding, while a plant in a 12 gallon planter will need more nutrient water to saturate it fully.
Read the cannabis fertilizer package carefully and follow what it says when it comes to recommended doses. You want to give your marijuana enough nutrients without causing fertilizer burn.

How often do I give fertilizer or water?

This depends on the grower preference, but in general you want to be feeding your marijuana at least once a week.
We recommend feeding plants Reefertilizer Grow or Bloom once a week and watering with correct pH water as needed, this keeps it super simple.
Others will split the weeks nutrients into two diluted feedings. Other growers like to feed plants two weeks on and one week off. Experiment with your plants and see how they react and what type of schedule you prefer. Reefertilizer is meant to be versatile in this respect.

Some big plants will need a feeding every few days. It depends on the needs of the individual plants. If you’re feeding a large plant once a week and it’s showing signs of a nutrient deficiency, as long as it isn’t being caused by a bad pH, you may need to feed them more often.

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What’s The Feeding Schedule for Cannabis?

All growers should use the instructions on their cannabis fertilizer as a guide. They will give you the best recommendation on the feeding schedule. The Reefertilizer schedule is a gradual approach. Start low and increase the dose every week until you get to full dose. This helps prevent any fertilizer burn, and starting with lower doses at the beginning of flower helps reduce nutrient buildup.

How do I Feed Cannabis?

Feeding cannabis can be very simple. It usually involves mixing a liquid or powder into some water and pouring that around the base of your plants.
With Reefertilizer Grow and Bloom you add a few scoops to some water and mix it up really well. It’s good to mix the powder with a small amount of water first to make sure it’s dissolved evenly, then add more water after.
It’s good practice to measure the pH of the nutrient water, this will help prevent nutrient lockout. If the pH is not in the desired range (between 6 and 6.8 for soil), use a product called pH up or pH down to adjust it. Natural ingredients like lemon juice and baking soda will also lower or raise the pH.

Reefertilizer products are meant to guide you through the cannabis growing process. Take a look at our free grow guide for more information.

How much fertilizer do I give?

If your unsure of how much you should be feeding your plants, start low and gradually increase the dosage every week. Don’t worry too much about over fertilizing your marijuana, that’s really easy to fix. If you see signs of fertilizer burn (brown tips and other symptoms), just flush your marijuana with extra water that week and start feeding them again when the soil is dry, but this time with a lower dose.

A Digital TDS Meter Will Help You Measure The Strength Of Your Nutrient Solution. | Learn More

When do I stop fertilizing my cannabis plants?

You want to stop feeding your plants a week before harvest. During this time your plant will utilize the remaining nutrients and energy in the plant for bud growth.
There’s a lot of debate on the topic of whether or not you should flush your plants with water during this period to leach nutrients from the soil and plant. Many professional growers say that flushing your plants a week before will improve the flavour and quality of your buds. Other professional growers say it doesn’t make a difference and they feed their plants right up to harvest.
In my opinion, flushing can’t hurt so why not give it a try. Do your own experiments and see what you prefer after drying and curing the bud.

Do I Need to Flush powder Cannabis Fertilizer Before Harvest?

If you’re going to flush your plants before harvest, you need to use plenty of water. You want to use enough water to fill your planter 2-3 times. That means if your growing in a 5 gallon planter, you need to flush it with 15 gallons of water. Soilless growing mediums like coco coir or peat moss are easier to flush, so you can use less water than with soil.
You can perform this flush once a week or more. I like to use a TDS meter to monitor the total dissolved solids in the flush runoff water. Each time I flush, that number should be getting lower.
Don’t worry about using pH perfect water for flushing. Since you will be harvesting soon, it won’t make a difference.

What Else Do I Need To Know About Cannabis Fertilizer?

Is Too Much Fertilizer Harmful?

It can be easy to go overboard with fertilizer products, but using more than what your plant can suck up will cause you problems. Depending on your plants size and the environment it’s in, there’s a finite amount of nutrients it can metabolize in a given period.
Using too much fertilizer may cause nutrient burn and symptoms of excess or deficient nutrients. If you over fertilize it’s not the end of the world. A good flush can bring most plants back to a healthy state.

Large outdoor cannabis yield
Cannabis nutrients

Why is There Growth or Bloom Fertilizer?

Cannabis plants have two major phases of growth; The vegetative stage and the flowering stage. The nutritional needs are slightly different during these two phases. Using the correct cannabis Bloom or Grow fertilizer will guarantee the correct level of nutrients the plant needs at that time.

Our free cannabis grow guide can help you find out when to start using fertilizer and when to switch to flowering nutrients

Try Reefertilizer Grow and Bloom for Veg and Flower. | Learn More

Can Nutrients Make Cannabis Taste Bad?

Many things can affect the final taste of cannabis, most importantly the drying process and the curing process.

Many growers will say that if a marijuana plant is not flushed properly before harvest it will develop a harsh taste not stay lit when rolled into a joint. Flushing could be a factor but perhaps a minor one. Cannabis will definitely get a bad taste if it’s dried to quickly or not enough. A lot of harsh flavours come from chlorophyll which slowly breaks down during the curing process.

What’s The Difference Between Organic Fertilizer And Synthetic Nutrients?

Organic nutrients come from a direct natural source. Synthetic are produced from natural sources but processed further to be more concentrated. If you compare the NPK ratio of organic fertilizers and synthetic, you will notice the numbers on synthetic fertilizers are higher. This is because the higher concentration from the extra processing.
Organic nutrients are slowly broken down by the root system. Since they are less concentrated, you need to apply them more often. An example of organic fertilizer would be compost tea which is made by soaking a permeable bag of compost in a large container of water.
Reefertilizer Start soil conditioner is organic and helps generate a healthy soil. This in tandem with synthetic fertilizers gives you the best of both worlds.
Synthetic nutrients are immediately available to plants and can give them a real noticeable boost in growth. Synthetic is usually cheaper and easier to use, but care must be taken not to over fertilize plants.

What is Marijuana Fertilizer Burn?

Fertilizer burn happens when you feed your marijuana plants too high a concentration of fertilizer. If left untreated it can seriously damage or kill a plant entirely. Good news, fixing an overtilized plant is really simple and done soon enough your plant will bounce back quickly.
To fix a plant that is over fertilized, flush the soil with 3 times the volume of the planter size. If you’re growing in a 5 gallon pot, flush with 15 gallons of water. What the water does is leach out any nutrient build up in the soil.
After flushing, give your plant about a week to recuperate, then you can start feeding them again.

Organic fertilizer

What is Nutrient Lockout?

Nutrient lockout occurs when the pH of the growing medium is in the incorrect range. Cannabis roots can only chemically metabolize nutrients if the soil is in a specific pH range. If the pH is too low or high, certain nutrients will be “locked out” and the plant will suffer from a nutrient deficiency even though they’re in the soil. Adding more nutrients won’t help and might cause a harmful build up in the soil.
Most cannabis problems start from an incorrect pH. If you see signs of nutrient deficiency in your plants, the first thing to check is the pH. Measuring and logging  the pH of the nutrient water is a good mesure to determine if you have a deficiency or a nutrient lockout.

How Do I Use Compost and Worm Castings as Fertilizer?

There are so many great things you can add to your soil that will help enhance growth and taste. Worm castings is basically worm poop, there’s also bat guano (also poop), and sheep manure (yes poop too), they are all great for adding to your marijuana growing soil.

Compost tea can be made by filling a permeable bag (potato sack) with manure and other compost and then soaking it in a large container of water. The water now filled with nutrients can then be fed to your marijuana plants.

Typically you would mix the compost with a potting soil or a soiless mix like coco coir or peat moss.
There are other things you can add that aren’t compost but benefit the roots. Using Reefertilizer Start in your soil will innoculate it with a helpful fungus. Adding perlite will help the soil hold oxygen and water.

Reefertilizer Start is an organic compost made from brown sea kelp. It can be added to your potting soil mix along with other composts and manures.
What these natural fertilizers do is slowly breakdown in the soil and feed your plants a variety of additional nutrients. These additions can affect the taste and quality of your weed and should be experimented with.

Try Reefertilizer Grow and Bloom for Veg and Flower. | Learn More

What About Slow Release Granular Cannabis Fertilizers?

Another option available are slow release fertilizer products. These can be added to the soil, or sprinkled around the base of the plant. The only problem with them is that if you use too much, you’re going to have a hell of a time trying to flush them out.
They are very popular for those who cannot tend to their marijuana on a weekly basis.

How Much Fertilizer Do I Give Autoflowering Cannabis Plants?

Autoflowering marijuana is ready to harvest sooner than photoperiod plants. Because of this they require less fertilizer products overall.
When it comes to autoflowers you’re best starting low and increasing a bit every week. If using Reefertilizer a medium dose is the higest you should go.

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