A cannabis plant needs a wide range of nutrients to grow strong, and healthily. Calcium deficiency in a cannabis plant will affect the uptake of many different nutrients. Calcium is used for many things in the growth of a cannabis plant. If your plants have a calcium deficiency, their growth can seriously be affected.

In this guide we will cover how to diagnose a calcium deficiency correctly, and how to fix the problem. Many growers will rush to assume a cannabis plant problem is calcium deficiency. Don’t rush, make sure you’re right in your diagnosis, so you can treat the plant for the issues it is having.

If you’re unsure of any deficiency, ask for help in our cannabis growers forum, and get advice from experienced growers. Do not be afraid to ask for help.

The Effects of Calcium Deficiency in a Cannabis Plant

Calcium is used through a plants life. It will help a seedling build its first tap root in germination, and it will help flowers form properly. Calcium is used to help with the uptake of nutrients, and the way the plant breathes.

When calcium is at optimal levels in a cannabis plant, it will remain in the cell walls. When there is a deficiency, it will dissolve and become mobile, as the plant tries to move it to where it’s most needed. This means, when a calcium deficiency in a cannabis first sets in, you will see changes in the middle, and older growth of the plant.

Stems will become weak and hollow. And they will snap easily. Your plant will also be more susceptible to heat stress, as calcium helps open and close the pores on the leaves (Stomata). If there is a lack of it, the plant can not breathe/sweat. This will affect the whole nutrient uptake of the plant.

If you have any questions about calcium deficiency in a cannabis plant, then feel free to ask for help in our cannabis growers forum

What Calcium Deficiency Looks Like

Like many nutrient deficiencies in a cannabis plant, calcium deficiency can look like many things. This is because calcium helps control the way food moves around the plant. Pay attention to the leaves in the middle and at the bottom of the plant for changes.

Symptoms of a calcium deficiency will first show with orange/ brown spots appearing on the leaf margins. This will be seen on the bottom half of the plant first, but will move around in extreme cases. Leaves will also twist and curl at the bottom of the plant.

You are unlikely to see a deficiency if you’re growing outdoors. But indoor growers will usually see signs of calcium deficiency around 2 or 3 weeks into the flowering cycle.

Knowing this, you can help prepare for your next grow, and supplement a little more calcium, just as you flip the light to flower cycle.

How to Fix Calcium Deficiency in a Cannabis Plant

The way you fix calcium deficiency will depend on what medium you’re growing in, but these problems are easily fixable! With any deficiency, it can be one of two things, either:

1: Your medium does not have enough calcium in it that is available to your plant.

2: The PH of your medium is off, and needs restoring so Calcium is within the correct range.

Calcium Deficiency in Coco & Hydro

When growing cannabis in hydroponic setups like DWC or coco, you are more likely to experience a calcium deficiency. This is because calcium will be best absorbed by your plant when the medium is at 6.0 – 6.2 ph. The optimum pH used in hydroponics, is 5.8, so sometimes, calcium can be slightly out of range.

Adding a cal/mag nutrient from one of your favorite nutrient lines will also improve the calcium content of your medium. But use it lightly, it is easy to overdose the plant and cause calcium excess.

As flowering approaches, it is a good idea to change your pH from 5.8, to 6.0. This will help more calcium be consumed during the time when the plant uses it the most. There may not be any need to increase the amount of calcium you’re feeding the plant, just restoring the pH can give the plant more.

Calcium Deficiency in Soils

It is less common to experience a calcium deficiency in a cannabis plant when you’re growing in soils. Soils have a good range of nutrients available to the plant, and can store it for a long time. If you feel as if your plant is suffering from a calcium deficiency you can treat the soil with:

Garden lime

Dolomite

Powdered bones

Crushed eggshells

Fish meal

Time will be needed for the microbes in the medium to break the nutrients down and make them available to the plant. It is better to try and offer the plant more calcium as they get older.

Bury some high calcium food, around a foot under your seedling or young plant before planting. A couple of fish heads will work great. This will give the plant the food it needs when the roots grow big enough to reach it. It also will have been broken down by the microbes, so it’s available to your plant when it is needed.

Final thoughts on Calcium Deficiency

The uptake of nutrients in a cannabis plant can be a complex process. Each nutrient will help another, and together they can grow a happy, healthy cannabis plant. If even one is off balance, the rest can soon start to follow. Keep the pH steady, and keep the EC low. Follow what your plant is telling you. If you need any help diagnosing a cannabis plant problem you can ask for help in our Plant doctors section of the forum.

Here you can find answers to your cannabis plant problems, direct from experienced cannabis growers. We have all had these issues before, don’t be afraid to ask for help from those who have been through it already.

Thanks for reading! You can find more information on anything related to growing in our cannabis grow guides. All of our guides are written by experienced growers, and members of our cannabis growers forum. If you have any questions, sign up. It is free, and we are always happy to help!

Together we can bring the best out of your cannabis crop! Stay safe out there, and happy growing.