A calcium deficiency in weed can spell disaster for your crops, especially if you grow indoors. It’s crucial for your marijuana plant’s health as it aids new growth and keeps its roots strong

While it’s simple to remedy, identifying this lack of nutrition is tricky as its symptoms copy many other cannabis deficiencies. If you notice any brown spots on your pot leaves or slowed growth, you need to act quickly.

Join us as we explain why this nutrient insufficiency occurs and what you should look out for. You’ll also learn how to fix a calcium deficiency whether you’re cultivating indoors or outdoors. Let’s dive right in!  


What is Calcium Deficiency in Weed?

A calcium deficiency in weed can pop up at any time of your crop’s life cycle. This nutrient is even required while your cannabis seeds begin to germinate, helping to facilitate root growth. As your plant ages, its need for this mineral increases.

Unlike other nutrients, such as nitrogen, calcium is described as immobile. This means that the mineral travels to the leaves, where it stays unable to move anywhere else. It’s, for this reason, that the early symptoms of calcium deficiency in cannabis show in new growth.

In a natural environment, a plant absorbs this immobile nutrient through the mineral-rich soil. This is predominantly why a calcium deficiency in weed occurs in indoor setups. 

We’re not saying outdoor cultivators can ignore this issue; it’s just less common.

Similar to how calcium strengthens our bones, this mineral is essential to root growth. Without it, your plants will struggle to absorb other nutrients, creating more issues like a magnesium deficiency in weed.   

A cannabis calcium deficiency will also make your plant more susceptible to pathogens. This is due to the mineral being a vital ingredient for reinforcing the cell walls in leaves.

Left unattended, a calcium deficiency in weed can cause severely stunted growth and slow bud development. This mineral insufficiency ultimately leads to a disappointing harvest and very poor quality yields.


calcium deficiency in weed


How do you Identify Calcium Deficiency in Cannabis?

Due to this immobile mineral’s importance, a marijuana calcium deficiency can present itself at any point in your plant’s life. You must keep a close eye on its development from the moment you sow the seeds.

There are several ways that a calcium deficiency in weed can present itself. You should watch out as these signs can mimic other mineral insufficiencies. Therefore you should try to identify more than one symptom before treating a calcium deficiency in marijuana.


Brown Spots on Cannabis Leaves

The first way to identify a calcium deficiency in weed is by the large, dark brown spots appearing on the leaves. You’ll also see the edges of your plant’s foliage turn brown. As time passes, both new and old leaves will begin turning a shade of yellow.

What’s more, a cannabis calcium deficiency will force your crop’s leaves to become deformed. If left untreated, the plant’s foliage will die and fall off. Remember that a cannabis zinc deficiency displays similar symptoms, so keep looking for signs to diagnose the issue. 


Stunted Growth

Another way to spot a calcium deficiency in weed is by your plant’s stunted growth. The reason this occurs is due to its root system becoming compromised. Your cannabis plant will struggle to absorb the necessary minerals, leading to nutrient lock.

During the vegging phase, you’ll notice your plant remaining small in stature. This becomes more evident in the flowering stage when bud development is also slow, similar to a sulfur deficiency in cannabis.

To confirm a calcium deficiency in weed, you can try to check on the roots for slime

You’ll need to do this without disturbing the plant, so remember to pay attention during transplanting.

You may also notice that your plants don’t respond well to heat. This complicates matters as, without sunlight, your crop will die.


Dead Spots

A calcium deficiency in cannabis also causes a plant’s stems to become weak and brittle. As soon as there’s an updraft of wind, these branches can break off, causing further injury to your crop. 

Again, this symptom appears in the case of a boron deficiency in cannabis. One way to tell these two mineral insufficiencies apart is by checking the center of the branches. A calcium deficiency in weed will show signs of rot inside the stems.


Young Leaves Grow Smaller

The last symptom of a calcium deficiency in weed shows itself in young leaves—this fresh foliage grows incredibly slow. They don’t display any signs of vigor, often losing their shape.

A molybdenum deficiency in cannabis also causes the new leaves to curl and deform. To avoid confusion, pay close attention to the color of new shoots. If you have a calcium deficiency in weed, these fresh stems appear purple or yellow.


Some Strains are more Prone to Calcium Deficiency

There are a few ways to remedy or even avoid a calcium deficiency in weed. However, some cannabis cultivars are more likely to show signs of this mineral insufficiency than others. This is because some varieties use up higher amounts of calcium.

One way this becomes evident is when you cultivate different cannabis types in the same area. You may only see a single plant displaying symptoms of marijuana calcium deficiency, while the rest look healthy.

It all comes down to the plant’s genetics. You’ll need to research the particular weed seeds you’re interested in growing to confirm whether it has any vulnerabilities.


calcium deficiency in weed


What Causes Calcium Deficiency in Cannabis?

For the most part, a calcium deficiency in weed presents itself as a direct result of the growing methods you use. To limit its occurrence, we look at these practices and why they can negatively affect your plants.


Using Filtered or RO Water

One of the biggest causes of calcium deficiency in weed occurs when using filtered or reverse osmosis (RO) water. This form of liquid is healthy for human consumption, but it’s not suitable for plants on its own.

The reason for this is due to the processes used to get this liquid. When creating RO or filtered water, we end up removing all the minerals present in it. This leads to you feeding your cannabis plants a solution lacking in essential nutrients


pH Is too Low

Another cause of calcium deficiency in weed is when you raise your crop in a growing medium with a low pH balance. If you germinate marijuana seeds in soil with a pH lower than 6.2, your roots won’t absorb any minerals.

At the same time, a pH balance over 6.8 will further damage the root system. Again, this leads to a nutrient lock and a calcium deficiency in marijuana plants.


Not Adding Calcium Supplements in Hydro and Coco

Not all cultivators raise their marijuana plants in soil. Many have chosen to use soilless mediums like coco coir or a hydroponics system. The issue here is that these substrates don’t naturally contain any minerals.

Soil contains all the nutrients a plant will need throughout its lifetime. While these methods hold many benefits for growing cannabis, you need to add supplements to avoid a calcium deficiency in weed.


Too Much Potassium

The last reason you’re experiencing signs of a calcium deficiency in weed is by adding a fertilizer that’s too high in potassium. An abundance of this mineral will create a toxic environment, so pay close attention to the ratios on fertilizer bottles.


Why are you Less Likely to Experience Calcium Deficiency Outdoors?

As we’ve already mentioned, you’re far less likely to come across a calcium deficiency in weed if you plant in an outdoor environment. Naturally occurring soil contains all the essential minerals your plant will need.

Using methods such as aquaponics is completely devoid of these essential nutrients unless you provide additional supplements. You should still test your soil’s pH balance if you cultivate outdoors to confirm the acidity levels. 

Here’s an easy way see your pH target: 

  • 6.1 pH = Too low
  • 6.3 pH = Balanced
  • 6.8 pH = Too high


How to Fix Calcium Deficiency while growing Indoors

If you prefer cultivating cannabis using the indoor method, there are a few ways to solve a  calcium deficiency in weed. Below, we look at how you can fix this lack of nutrients depending on the growing medium you use.


calcium deficiency in weed


In soil

As we’ve already pointed out, using natural soil is one of the best ways to avoid a calcium deficiency in weed altogether. However, you can run into a few issues if you don’t provide the right fertilizer while growing indoors.

If you start to see signs of cannabis calcium deficiency in your crop, don’t panic. You can add dolomitic lime to your potting soil. This won’t only rectify the pH balance but also provide your plants with additional calcium.


In Hydroponics

Since a calcium deficiency in weed occurs more often in hydroponic setups, it’s in your best interest to learn how to fix the issue. Luckily, these steps required to do so are very straightforward.

You need to ensure your solution contains more than 150 milligrams per liter of dissolved solids, for starters. If not, you should add calcium and magnesium into the water to achieve this reading.

If your solution’s pH balance is outside the appropriate range, you’ll likely cause a calcium deficiency in weed

All you need to do is flush your system and add water with the correct values. You can then add a teaspoon of liquid calcium per gallon to solve the problem quickly.


In Coco Coir

Like hydroponics, you can experience a calcium deficiency in weed when using soilless mediums like coco coir. To solve this issue, you’ll need to pay attention to the pH level and add nutrients.

Maintaining a balanced pH in your coco coir will allow your plants to absorb the minerals you provide. If you need to correct it, rinse the medium in water containing an opposite level. For example, if your pH is too low, you’ll need a more alkaline solution.

It also helps to flush the coco coir before adding a calcium supplement. This removes any excess salts and the chances of nutrient burn.


Stop Calcium Deficiency in Cannabis from Becoming a Problem

It’s not difficult to fix a calcium deficiency in weed. At the same time, there are a few ways that you can avoid the issue altogether. For the most part, these steps will assist indoor cultivators, but you’ll find something to help you no matter what technique you choose. 

  • Use the correct type of lights. Some bulbs for indoor growing, like LEDs, don’t emit the required light spectrum to produce calcium.
  • Regularly test the pH levels of your growing medium.
  • Use spring water for its high content of calcium and other minerals.
  • Give your plants additional supplements, especially when using a hydroponics setup.


Your cannabis plants need their vitamins too!

Marijuana needs calcium throughout its lifetime. Without it, your plants stand the risk of becoming sick and weak. There are many ways to solve and even prevent a calcium deficiency in weed.

Don’t over supplement your plants, as you could end up with calcium toxicity in cannabis instead. Remember that results aren’t instant, so you’ll need to exercise some patience and learn from your mistakes.

Posted in: View allTroubleshooting