Yellow Cannabis Leaves
3 min

How To Treat And Avoid Yellow Cannabis Leaves

3 min

The sight of a luscious and thriving cannabis plant is enough to bring a smile to the face of any grower. Therefore, spotting yellow leaves is a cause for concern. But worry not, here are a few ways to tackle some of the major causes.

Growing cannabis isn’t always an easy and smooth process. Achieving an end result of dank and pristine buds often requires growers to overcome numerous challenges and hurdles. Although these can often be a pain and a source of pessimism, they ultimately serve as learning experiences that make growers better at the art in the future. Luckily, cannabis plants have their own way of displaying warning signs. These small cries for help serve as a compass for growers and lead them in the right direction to bring their crop back to optimal health.

One key sign to look out for is yellow leaves. It can be quite worrying to enter the grow room or garden and spot a few feeble and yellow leaves among an otherwise green and flourishing canopy. Yellow leaves have numerous different causes. It’s important to identify what may have caused for these to occur, in order to efficiently treat your plant. Here are the top 5 reasons for yellow leaves and how to treat them.


cannabis ph measuring

Acidity or alkalinity of a growing substrate is expressed with a pH figure, with different substrates requiring different levels of pH. Plants grown in soil thrive in an optimal pH of 6–7, whereas plants cultivated within a hydroponic set-up prosper in a slightly more acidic pH of 5.5–6.5. Maintaining these specific pH values is essential when it comes to nutrient delivery. Within these ranges, cannabis plants will have no problem absorbing nutrients through their root systems.

However, if for some reason the pH fluctuates past these ranges, a phenomenon called nutrient lockout can occur. This condition results in difficulty for the roots when it comes to absorbing nutrients, which can eventually cause deficiencies. Yellowing leaves is a tell-tale sign that root lock is occurring in the rhizosphere. As well as appearing yellow, leaves may also display spots and burning around the edges.

To prevent pH imbalance from occurring, it's a wise idea to invest in a pH pen or kit that can measure the pH of your water source. If the pH is within the acceptable range, then go ahead and water away. If it’s too high or low, then add pH up or down products into the water, until it hits the sweet spot. Another way to ensure correct pH is to invest in “pH perfect” nutrients that remove the need to continually monitor water pH before administering fluid to plants.

To treat plants that are already presenting with yellow leaves, flush them using pure water with optimal pH before resuming feeding with correctly dialled nutrients.

Related article

How To Adjust pH Level When Growing Cannabis


burned cannabis leaves

An adequate light source is essential for obtaining yields of maximum quality and quantity. As we all learned in biology classes, light is required for plants to conduct photosynthesis in order to produce glucose as a source of fuel for survival. However, there can be too much of a good thing.

Lights should be optimally positioned above an indoor cannabis crop throughout the entire grow cycle. If the lights are placed too far away, then your plants will be missing out on maximum glucose synthesis. If the lights are positioned too close or plants go through a sudden growth spurt without light distance adjustment, growers run the risk of burning the leaves. This occurs when too much heat is emitted to the leaves, turning them yellow. To avoid this, be sure to position your lighting set-up within the distance suggested by the manufacturer. Continually monitor your plants throughout the grow cycle for any signs of yellowing and adjust lights accordingly.


watering cannabis plants

Much like light, water is an essential element to the correct growth of cannabis plants. Watering may seem like one of the easiest aspects of maintaining a cannabis plant, but it’s not to be underestimated. Underwatering is relatively rare, however overwatering is very common and is often done out of excess care.

Cannabis plants are relatively hardy creatures and should only be watered once the top layer of soil has become almost totally dry. Lack of drainage can also cause water to pool at the bottom of containers. Both underwatering and overwatering can lead to yellow leaves. Other signs of underwatering include drooping, whereas overwatered plants will appear to have overly fat and plump leaves.


hot temperatures cannabis plants

Excess periods of hot temperatures in the garden and overly warm conditions within grow rooms can cause yellow leaves to occur. Temperatures that exceed 28°C can be hostile to cannabis plants. If your outdoor crop begins to show yellow leaves, consider moving the plants into a patch of shade and into an area that is more likely to receive draught. If you begin to lose control of indoor temperatures and your cannabis leaves turn yellow, then consider investing in an air conditioning unit or a fan to bring the temperatures back down to tolerable levels


cannabis plant pest invasion

One of the biggest threats to outdoor cannabis plants is pest invasions. Many different insect species have a taste for juicy cannabis leaves and stems. The stress and damage from such an attack can cause leaves to turn yellow in colour. Other symptoms include spotting eggs and bugs, and general structural weakness.

Related article

Common Problems In The Cannabis Garden

There are many different methods of deterring pests from munching on your valuable crop. Recruiting predatory insects such as ladybugs and praying mantis will serve as a natural way to keep pests' numbers down. Companion plants are also a great way to distract insects from your cannabis plants.

Luke Sumpter
Luke Sumpter
With a BSc (Hons) degree in Clinical Health Sciences and a passion for growing plants, Luke Sumpter has worked as a professional journalist and writer at the intersection of cannabis and science for the past 7 years.
Growing Seedshop
Search in categories