Blood Meal For Cannabis

Learn to use blood meal with cannabis plants. Provide them with high amounts of nitrogen, very much needed during the vegetative stage. Find out exactly what is blood meal, how to apply it, and precautions for cannabis plants. Let's get into it.

What Exactly Is Blood Meal?

Blood meal is fertilizer full of organic nitrogen that comes from animal blood, and has been widely used for the cultivation of food for ages.

Blood meal is one of the most nitrogen rich organic amendments and contains approximately 13.25% nitrogen, 1.0% phosphorus, and 0.6% potassium. Usually depicted as NPK 13-0-0.

Since hemoglobin is the main content of blood meal, there's also a lot of iron to be found in it. More than enough iron to keep your plants feed and healthy.

Blood meal
Blood meal is a great source of nitrogen for plants

Is Blood Meal A Good Organic Choice For Cannabis?

Yes. And it is perfect if you're facing a cannabis nitrogen deficiency

However, it will not provide a balanced diet. Blood meal gives high nitrogen levels almost exclusively, which can mess your plant during flowering.

If you need a consistent, steady supply of nitrogen during the vegetative stage, definitely go for it.

Not to be confused with "bone meal" that is used for flowering due to the contribution of phosphorous.

Blood meal fertlizer
Blood meal fertilizer

How To Apply Blood Meal

I recommend blood meal only for those who are used to fertilizing since it can turn the soil too acidic or create nutrient burn very easily.

Be very careful if you're growing in indoors, as outdoors there's more room for error, but adding blood meal to pots can seriously damage your plants if you're not careful.

Before adding blood meal, I strongly encourage you to test your levels of pH, and to keep monitoring it after fertilizing. You don't want your soil getting too acidic.

Also, make sure to read the package instructions to see if the specific fertilizing method recommended by the brand matches your needs.

Mixing It With Water

If you have your cannabis plants in pots, you would definitely want to add the blood meal via watering, as you don't want to overdo it and the amount of soil in a pot in very limited.

  1. Fill a bottle to 10% of its capacity with blood meal.
  2. Fill the rest with standing water.
  3. Mix well and let stand for a while.
  4. Mix again from time to time and open the lid to let out the gases that are created.
  5. Wait a day or two until there are no solids in the bottle.
  6. Mix the contents of the bottle again with standing water, at the rate of 1 part of solution for every 10 parts of water. (10% and 90%)

With this new double-diluted solution you can now fertilize your plants.

Adding Blood Meal To The Soil

You can mix blood meal directly into the top inches of the soil, being really careful not to hurt any root while removing the soil.

The good thing about blood meal is that you only need to add a little. It will stay on the soil for a really long time, and your cannabis plants will keep benefiting from it.

As a rule of thumb the rate of blood meal you want to use is one cup for every twenty square feet of soil.

How Often To Add Blood Meal?

When mixed with water blood meal is quick to act, I would suggest watering with it  once a week as long as your plants need nitrogen. (If they're green and healthy, nitrogen is going fine!)

In soil, it will slowly break down with time. And since blood meal is water soluble it can still can act fast to correct nitrogen deficiencies. Once applied, blood meal can feed your plants for 6-8 weeks after a single application.

Precautions For Cannabis Plants

Blood meal releases nitrogen very quickly thanks to being a very thin dry powder, so please be very careful when you apply it.

Do not use it with seedlings unless you're experienced. And with more mature plants be cautious not to apply blood meal more than 2 times a week (specially on pots), otherwise you run the risk of seriously harming the root system.

Is It Safe To Use Blood In My Garden?

It's perfectly safe. As long as you're getting it from a trusted source, then the blood should come from healthy animals.

This is mostly from cattle or hog blood, and is a slaughterhouse by-product.

False: Blood Meal And Mad Cow

There are rumors and panic around this, but are only that, rumors. I could not find one article, study or research that correlated mad cow disease to growing cannabis or growing food, in any way.

Only that the FDA ban on use in feed for cattle and other ruminants.

Watch Out For Wild Animals Or Even Pets!

You do have to be very careful if you have animals living around (specially outdoors) as the smell of blood meal can sometimes attract wildlife or pets, and you don't want to get up and see your plants have been dug up. Specially in skunk or raccoon territory

"If you use blood meal outside you are asking for trouble. It might never happen, but if an animal finds it they are going to dig for it. Like if you bury a sandwich under ground, and a dog walks by it will get dug up. Why take the chance?"
User on THCFarmer

Blood meal works, but why use it outside when there are other solutions that are as effective and won't get you in trouble.

What Are The Alternatives To Add Nitrogen?

Personally I prefer to use worm castings for nitrogen. Earthworm castings are full of organic matter and microorganisms that give you great benefits on top of fertilization.

Worm castings contain essential nutrients such as nitrogen, phosphorus, and potassium, which are vital for plant growth. In addition, they also contain lower levels of iron and other micronutrients, ensuring that your plants receive a balanced and complete diet.

Unlike blood meal, worm castings are less likely to cause nutrient burn and offer a wide range of benefits, making them an excellent choice for fertilizing cannabis plants. To delve deeper into essential nutrients in cannabis growth, take a look at my guide on Essential Nutrients in Cannabis Growth.

Worm castings
Worm castings

Hey there, I'm the person behind this website. I started growing cannabis in 2014 right after marijuana was legalized in my home country. Today, on, I address growers need for knowledge and show you how to grow cannabis plants and enjoy amazing buds.

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