calyxes not swelling

Calyxes Not Swelling? Don’t Know What To Do?

Once I planted Cannabis Sativa in a grow tent and waited for 7 months for flowers. Unfortunately, I couldn’t get anything from that batch. Later I realized it didn’t produce any flowers because the calyx of the plant did not swell. 

Is your plant’s calyxes not swelling as well?  

It happens if the temperature of the tent isn’t set properly. Calyx can’t swell in colder temperatures. The swelling of calyxes sometimes becomes slow due to heavy humidity. The calyxes fail to swell if the blooming light is far away from the plant. Soil and nutrition’s pH level also causes this.  

If you’re looking for the reason and solution behind this issue, you’re in the right place. Stay with us, we will try our best to help you out. 

How Do You Know Calyxes Not Swelling?

When calyxes swell, it indicates that the bud inside the calyx is maturing. If the bud is maturing, you are some weeks behind from harvesting. It usually takes 8 weeks for a calyx to swell fully.

You have planted your cannabis plants inside your grow tent. It takes 2-8 weeks for vegetative growth. After this vegetative growth, it takes 8-10 weeks for flowers to bloom. 

Before flowering, the pre-flowering stage lasts for 1 or 2 weeks. That’s when calyxes swell and start to mature. The swollen calyx looks like thick leaves beneath the flowers.

The swollen calyx

You will notice some pistil hair above the plant on the pre-flowering stage. If there’s no pistil hair grown at the flowering stage, it means calyx didn’t swell. 

But if the calyx swelled during the pre-flowering stage, it would start to grow pistil hair. Pistil hairs help the plants to pollinate. 

So, you’d know that calyxes didn’t swell if there’s no pistil hair after 6-7 weeks.

Swollen calyxes

Why Calyxes Not Swelling?

Calyxes are expected to be swollen every time cannabis seeds are planted. It takes about 6/7 weeks for calyx to swell. Swollen calyxes indicate that the bud is maturing inside. 

If the bud is maturing, the flower will start to bloom soon. But that doesn’t happen all the time. This issue happens for various reasons. 

As a result, all your hard work would go in vain. But some measures and preventions can be taken so that this problem never occurs.

Reason 1: Improper Temperature

Calyxes can not swell in low temperatures. The buds mature at a fixed temperature. The temperature has to be set within 75-88 degrees Fahrenheit. 

Calyxes hardly swell if the temperature is less than 75 degrees Fahrenheit. Soil temperature can also create this scenario.

Solution 1: Set The Right Temperature

We know that cannabis can not grow in colder temperatures. If you are growing cannabis inside your Grow-tent, make sure you set the right temperature. 

The temperature for the calyx to swell should remain within 75-88 degrees Fahrenheit. If the temperature is lower than 75 degrees Fahrenheit, the calyxes fail to swell. 

On the other hand, it is seen that calyx actually swells perfectly in slightly warmer temperatures. It helps to get more yields if the temperature is a bit higher.

You can use these digital thermometers to ensure the proper temperature in your grow tent.

Reason 2: Humidity Adjustment

Cannabis calyxes don’t swell if the humidifier isn’t properly placed. Humidity inside the tent has to be 60-80%. 

Calyx won’t swell if the humidity is too much. If the humidity is high, the swelling of calyx will be really slow.    

Solution: Set the Perfect Humidity

Humidity plays an important role for cannabis to grow and produce flowers. So humidity must remain within 60-70%. If the humidity rises, the growth of the plant will be slow. 

If the humidity is at the highest spectrum then you should use a dehumidifier. I use the VIVOSUN Small Space Mini Dehumidifier for my grow tent. It’s perfect if 3×3 or a 4×4 grow tent.

Also, you have to make sure the humidity is 60-70% inside the tent. That is during the vegetative growth stage. 

In order to increase the humidity inside your grow tent I would recommend using the VIVOSUN Cool Mist Humidifier. That’s because I am already using a dehumidifier from this brand and it’s giving me great service.

Here’s a pro tip, no matter which one do you need or both you must use the Inkbird Humidity Controller IHC200 Humidistat. You can plug both your humidifier or dehumidifier to it. And it’ll control the optimum humidity by switching them on and off.

Reason 3: Light Adjustment

For Indoor gardening, LED lights or blooming lights are a must. 

The placement of the lights plays a vital role to help the calyx swell. It happens sometimes if the lights are kept turned on more than the required time. 

The growth of calyx gets hampered when it is exposed to too much light and hit. 

Solution: Make Sure Proper Lighting Arrangement 

Indoor gardening requires Blooming or set-up of indoor LED lights for the growth of the plants. The lights shouldn’t be far away from the plants. It should be set within 12 inches from the plant. 

Though it varies on the type of lights you are using. 

The light should be turned on for 8 hours and turned off for 8 hours a day. There’s another method of keeping the lights on and off for 12 hours. 

The lights should be on for 18/20 hours for vegetative growth. It should be off for 6/4 hours. If the lights are always kept turned on, it will hamper the normal growth of the plants. 

These types of plants are known as short-day plants. So, the plants should be kept in darkness for some hours.

With the proper amount of lighting hours and its set up, cannabis calyx will swell perfectly. Also remember to keep the wavelength required in different stages in mind while using lights.

Proper Lighting Arrangement

Reason 4: pH Level of Soil Nutrients

The improper pH level of nutrients can also be the reason why calyxes are not swelling. When the pH level is not between 5.6 to 5.8 swelling of calyxes gets interrupted. 

This problem might appear if the pH of the soil is not 6.5. Having a optimum pH will make sure there is proper number of micro organisms. It also entangled with the amount of CO2 emission.

Solution: Measure The ph Level of The Soil and Nutrients

External soil and nutrients like Miracle Grow perlite are needed while growing cannabis inside your grow-tent. 

Make sure the pH level of the nutrient doesn’t exceed 5.8. You can use the SONKIR Soil pH Meter to find out the pH of your soil.

SONKIR Soil pH Meter

If it increases it means the nutrient is more acidic. The pH level of the nutrients often fluctuates after mixing it with soil. 

So always keep checking the pH level of the soil and nutrients.

Never decrease the amount of Carbon Di-Oxide that is required. The calyxes of the plant need proper nutrition and Carbon Di-Oxide in order to swell. 

So, the right amount of Carbon Di-Oxide should be present inside the grow tent. 

Reason 5: The Amount of Carbon Di-Oxide

Imbalance of carbon-di-oxide gas inside the grow tent can hamper the growth. If the level of carbon is less than 800 parts per million, calyxes might not swell. 

A small amount of carbon-di-oxide means less photosynthesis. This leads to malnutrition of the cannabis plants.       

Solution: Ensure Proper CO2 Level 

Make sure there’s enough CO2 inside the tent. 

You can add an external source of CO2 such as Exhale. Another way is that you can provide nutrients that contain CO2.  

Why is it Important that Calyxes should Grow?

Calyxes are important to grow or swell. A lot of you wonder whether swollen calyx good or bad. It’s a good thing. 

If the calyx of a plant swells it means the bud inside the calyx is maturing. The buds need to be matured to produce flowers. These mature buds grow pistil flowers in the pre-flowering stage. 

This early flowery pistil helps to pollinate the plant. 

We want to achieve the complete product from the cannabis plant. So, it’s necessary that the calyx of the cannabis plant swell perfectly. 

It’s one of the important stages of a plant’s normal growth. If it’s needed, add extra nutrients with soil like canna boost or its alternatives. So that the calyxes swell on time. 

Frequently Asked Questions (FAQs)

How can you tell if a Calyx is pollinated? 

First, grab a pair of tweezers if you’re not sure if the bract is swelling. Check if there is an immature seed growing inside by cracking it. If so then you have a pollinated plant. It is fair to presume that no pollination took place when no seed forms. The calyx size remains relatively unchanged.

Can you smoke Calyxes?

Yes, you can! Cannabis resin buds are frequently formed and secreted in the calyx. Similar to the calyx itself, sugar leaves are thickly covered with trichomes. However, the calyx has a high concentration of cannabis resin. This makes it the best option for smoking.

What does Calyx look like?

A single element that resembles a leaf, is known as a sepal. And it makes up the calyx of a flower. The outer layer of the flower’s bud is still forming before it blooms.


Calyx is an essential part of cannabis. It has to swell in order to produce the final product that we get from this plant. Now we know why calyxes not swelling and why it’s important for calyxes to swell. 

Rember not to overheat your plant which may result in retarded plants. Never make a clone plant a mother plant.

Thanks for staying with us till the end. Hope this was helpful to you!

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