Calcium Deficiency on Cannabis

Free the tree content
Calcium deficiency – What are the signs? What to do? thumbnail

Identifying and Solving a Calcium deficiency

Hi there and welcome (back) to Free the Tree!

In today’s article of our Nutrient Deficiency series we decided to finally cover Calcium Deficiency on Weed.

This is now the third deficiency our plant’s gone through.. I think the issue is with the medium we planted the BBC in, we didn’t give it time to rest..
Regardless, this time around the Big Buddha Cheese plants that had Potassium and Phosphorus  deficiencies now need more Calcium… Loosing a lot of leaf mass which sucks.
Here’s what we’re going to cover

What do plants use Calcium for?

Calcium is one of the 3 main elements that all flowering plants need to thrive. For full disclosure, plants need about 28 different nutrients in order to thrive, most of which are produced by micro-organismes present in the soil.

Calcium is one of the secondary nutrients necessary for plants to grow. Its main use is holding together the cell walls of the plants. When plants don’t have enough calcium new tissue such as root tips, young leaves, leaf and shoot tips often exhibit distorted growth from improper cell wall formation.

Calcium is also used by certain plants to activate enzymes and send signals that coordinate certain cellular activity.

Even though it’s considered as a micro-nutrient, for some plants like tomatoes, calcium is one of the most important nutrients.

We’ll cover this more in detail further down, but Calcium Pectate is not a mobile element, meaning that plants depending on their transpiration process to move it around.

Calcium in Cannabis - Uses during Vegetative and Flowering Stages

 Flowering and Vegetation
  •  Holding Cell Walls, especially in new growth
  • Immobile element
  • Enhances the decomposition process of organic matter which will improve the uptake of nutrients by plants.
  • Acts as bridge between humus and nutrients
  • Activates enzymes and signals that coordinate certain cellular activity

What Is Calcium Deficiency?

As the name indicates Calcium deficiency is a sign that the plants roots cannot access the Calcium available or that there isn’t enough available.
Another situation could be that your manganese levels are too high, reducing your Ca/Mn ration.

We won’t go into the technical details here but Calcium and Manganese availability are correlated, meaning that if one is too high the other won’t be as available.

So to recap, Ca Deficiency can occur when there isn’t enough Calcium (less than 40-60 ppm), the pH is off or the level of Manganese (Mn) is too high.

A problem growing your plant ?

We help you with a free diagnostic

Get a free diagnostic
A problem growing your plant ?

Contribute to our knowledge base

Submit articles, videos or tips to enrich our library

Make a contribution
Contribute to our knowledge base

At which pH level is Calcium available?

As you may know different nutrients are available at different pH levels.
Thankfully for plants on earth, all the nutrients are accessible at a pH between 6 and 7.

Calcium itself is really available to the roots between 6.3 and 9, so if you have an Ca issue aim for a pH around 6.8-6.8

If you want to review the pH levels for each nutrient and how to measure check out our table available in our piece on watering your marijuana plant

The 12 main nutrients necessary for marijuana and their pH level availability
pH levels per nutrient

How to identify Calcium Deficiency on Cannabis?

As we’ve started saying in the intro of this piece, and as it goes with most deficiencies, the signs will show up on the leaves.
To help you out as best as possible we cut this part in 2 sections:

What are the signs of Calcium deficiency?

Depending on how far along the deficiency is and the stage of growth you’re in the signs may differ slightly, especially on the new growth part.
But globally here are the main signs of Ca deficiency

  • Oddly formed new growth; Whether it’s new shoots, leaves or roots
  • Brown/Yellow/orange-ish spots show up all over the leaves, attacking especially the fan leaves.
  • Leaves and stems are very weak; They break/fall off very easily.
  • These spots will grow and the leaf will start to curl up
  • From the tip down the leaf will be brown and dead.

Evolution of Calcium deficiency

The lack of Calcium is a creeper, the early signs are very subtle and are mostly visible on the new growth, but once it starts being visible on the main leaves it comes in quick and fast.

Here’s the evolution of a couple of our leaves

Summing up – Diagnosing Calcium Deficiency

Calcium deficiency will show up in the following ways:

  • New growth may be oddly shaped.
  • Brown/yellow spots will appear all over the leaves
  • Leaves will curl up and die
  • Calcium works with Manganese, too much of one and the other isn’t available anymore.
  • After implementing “fixes” deficiency should stop spreading within a week
  • Impacted leaves will not recover

How to solve Calcium Deficiency on Weed?

Depending on the reason why you have this calcium deficiency your response will vary.
If you think your soil’s used up and doesn’t contain sufficient levels of Calcium, add a Ca-Mn nutrient mix to your next watering solution.

You should see effects stop within the next week.

In the case where you’re pH levels have been too low, raise them for your next watering (don’t do this too drastically! or else you’ll create pH issues on top of it)

And finally if the issue is related to high Manganese levels you’ll need to add pure Calcium solutions.

How to treat Calcium Deficiency organically

In order to treat calcium deficiency organically you’re going to want to take care of your soil. A happy (and living) soil is a happy and healthy plant 🙂

Ok cool, but what does that mean? Well it means trying to think differently, finding where Calcium is naturally in nature and provide it to your soil in a way your plant can assimilate the nutrients. Sooo the question is now, where can we easily find something that has Calcium and that can be broken down small enough to mix into the soil…… Egg shells !

Most Common Reasons for Calcium Deficiency

The main source for Calcium deficiency is pH issues or low quality soil.
As we stated earlier, calcium can be best taken in a pH levels between 6.3 and 9 so if your watering mix is too acidic then it’s not available.
The second main reason for this are soils not containing enough Calcium or too much manganese. In that case just adapt your watering mix as instructed in the previous section of the article.

For quick relief you can also spray the leaves with a Ca concentrated mix about 15 minutes before lights out.
Since Ca is an immobile nutrient the leaves won’t take in much, but just a little will help ^^

Can't find what you are looking for?

Tell us how we can help out

Make a request
Can't find what you are looking for?

Can't find your answer?

Send us your question

Can't find your answer?

That’s it for this one folks.
Until next time, be safe and grow easy!

About the author