Feb
How To Grow Marijuana Seeds
Cannabis Leaves Turning Yellow – Causes & Solutions
The issue of yellow leaves affects not just cannabis plants but also other types of plants. But when you have invested time, money, and effort toward cultivating marijuana plants, seeing yellowing leaves among your crops can induce panic.
But before you worry about your cannabis plants, it is essential to pinpoint the underlying reason behind the yellow leaves. This will help plan the proper course of action and ensure the health of your plants.
What Do Yellow Leaves on Cannabis Plants Mean?
What does it mean when cannabis leaves turn yellow? The truth is, there is no single reason why cannabis leaves turn yellow. That, however, does not necessarily mean that your plants are dying or that you cannot turn things around.
Yellowing leaves in marijuana and other plants can be attributed to a phenomenon known as chlorosis. Essentially, this means that the affected leaves have lost their chlorophyll content.
All plant leaves, including those of the cannabis plants, contain cells known as chloroplasts which include the familiar green pigment of leaves. However, plant leaves may also have other pigments, like orange and yellow carotenoids. The green pigments overshadow these pigments because of their higher volume in the leaves.
Chlorophyll plays a pivotal role in helping plants absorb and process sunlight into energy. This process is known as photosynthesis. When your marijuana plants are healthy and thriving, they have green leaves. However, when your plants are under stress, their leaves can turn yellow.
Yellow leaves cannot absorb and process sunlight like chlorophyll. As such, they need to turn to chlorophyll for help in photosynthesis. When plant leaves are just turning yellow, photosynthesis can still happen. However, when the yellowing of the leaves is in the advanced stage, plant growth can become stunted. Worse, your plants can die if you cannot pinpoint and address the underlying reason.
How to Identify (and Fix) the Cause of Yellow Leaves
The last thing that you want to do after seeing yellow leaves on a cannabis plant is to panic. More often than not, that is unnecessary. The right thing to do is to evaluate the affected plant so that you can determine the correct measure to solve the underlying cause.
Here is a list of potential reasons why you are seeing yellow leaves on your cannabis plants as well as the appropriate actions that you can enforce to turn things around.
- Senescence
Like most living organisms, marijuana plants undergo aging. One of the signs that your crops are aging is senescence.
In other plants, senescence is associated with the changing color and falling of their leaves during the autumn season. In marijuana plants, senescence can manifest itself in the form of yellow leaves, typically during the flowering stage. At this point, your plants divert their energy toward developing and growing their buds.
What you can do
There’s not much that you can do to prevent senescence among your crops. It just works that way. However, expert cultivators usually flush their plants during the tail-end of the growing season. This allows the plant to wash away excess nutrients and hasten senescence.
- Nutritional issues
While cannabis plants do not need much to grow, they can immensely benefit from proper fertilization. However, if you have not dialled in your plants’ nutritional requirements, you can face a few issues, including cannabis leaves turning yellow. Nutrient deficiencies and overfeeding can both cause damage to a cannabis plant. And as such, it is vital to know which specific issue is affecting your crops.
Signs to watch out for
Aside from yellow leaves, plants that are over-fertilized have crunchy and curling leaves. On the other end of the spectrum, plants with nutrient deficiencies have wilted and yellow leaves.
What you can do
Although cannabis plant nutrition is no rocket science, it is fairly easy to over or underfeed your crops. One useful trick you can use to ensure that your plants get the right nutrients at the proper ratios for a specific growth stage is to check the label of the fertilizers you use. This simple trick is more than enough to keep nutrient deficiencies at bay. Another important thing to remember is that the nutritional needs of your plants change as they proceed from one growth stage to another.
- Over or under watering
When it comes to watering your plants, there are no clear rules to follow. Determining the exact water to give your plants can be quite tricky because you need to take into account environmental factors like heat and humidity into account. As such, it is no surprise that over and under watering count as two of the most common reasons for yellow cannabis leaves.
Signs to watch out for
Some of the signs of over and under watering your plants are similar, including leaves that turn yellow.
However, there are a few key differences. In an under-watered plant, you will notice that the leaves are wilting due to the lack of moisture content. In an over-watered plant, the leaves are drooping because the plant cells are filled with an excessive amount of water.
What you can do
Most under-watered plants recover quickly as long as you provide them with sufficient water as soon as possible. With over-watered plants, you have to stop watering them until their substrates dry.
To avoid both issues, you need to determine the sweet spot when it comes to cannabis irrigation. As a rule of thumb, it is best to check the substrate before you water your marijuana plants. You will know that your plants need to be watered when the top inch of the soil is completely dry.
- pH imbalance in the substrate
Finding the right substrate pH level ensures that the nutrients in the soil are absorbed by your cannabis plants. If the pH level of the soil is beyond the appropriate range, your crops will have a difficult time accessing and absorbing the nutrients they need. This phenomenon is known as a nutrient lockout.
Signs to watch out for
A pH imbalance in the substrate can manifest itself in yellow cannabis leaves. But aside from the noticeable discoloration of the leaves, you will also see a few telltale signs including burnt leaf edges as well as patches on the leaves. However, the best way to determine if there is a pH imbalance in the substrate is to conduct a test.
What you can do
Marijuana plants prefer a soil pH level between 6.0 and 7.0 and 5.5 and 6.5 for coco coir and hydroponic setups. Ideally, you should check the pH level of the substrate and make the necessary amendments a few weeks or months before the planting season. This is the best way to avoid a pH imbalance.
But if you discover an imbalance during the planting season, you can try using products that are specially formulated to increase or decrease the pH level of substrates. Before using either of these products, be sure to check the water pH level in your area as this can affect the final outcome of this remedy.
- Root rot
Another potential reason why you are dealing with yellow cannabis leaves is root rot. Root rot arises because you are over-watering your plants, leaving them vulnerable to microbes that target the roots.
Signs to watch out for
Aside from leaf yellowing, one clear sign that a plant has succumbed to root rot is that the roots have turned brown and slimy. If you suspect that your plant is suffering from this issue, take it out of its container to inspect its roots.
What you can do
Root rot can be treated but you have to act quickly. The first thing that you need to do is stop watering the affected plant ASAP. Next, allow the substrate to dry completely, giving the affected plant the opportunity it needs to recover. After that, you can add beneficial microbes to fight off the infection and facilitate complete recovery.
To prevent future bouts of root rot, make sure that you avoid over-watering your crops. It is also beneficial to use fabric pots that improve drainage and facilitate air circulation in the roots.
- Pest infestation
Pests can make quick work of your cannabis plants, rendering your efforts fruitless. Fortunately, you can put up a serious fight and turn the tides in your favor.
Signs to watch out for
Insects and other pests affect plants in various ways. However, they usually target the plant leaves. Aside from leaves that turn yellow, an infested plant has shriveled leaves. In some cases, you can even see the invading pests on top of the leaves having a hearty feast.
What you can do
There are various pesticides that you can try to treat a pest infestation. Alternatively, you can use neem oil if you prefer to avoid using harsh chemicals on your plants. All you have to do is to apply these products to the leaves of the affected plants. If you want a less invasive approach, you may want to introduce predator insects to deal with pesky pests.
- Temperature extremes and fluctuations
The temperature requirements for cannabis strains vary from one another. However, most cultivars thrive within a range of 20 to 28 °C. If your plants are subjected to too much heat or cold or temperature fluctuations, whether you grow them indoors or outdoors, the marijuana leaves can turn yellow.
Signs to watch out for
Marijuana leaves that turn yellow due to inconsistent or extreme temperatures have curled and yellow leaves that are close to wilting. But aside from that, you will also notice that the substrate is completely dry.
What you can do
If you are growing your crops outdoors, check the area where you planted them. Specifically, you need to determine how much direct sunlight they are getting. This is particularly important if you live in an area with a warm climate. Your priority is to stop overexposing your weed plants to excessive light and heat while providing them with sufficient moisture. You can also move your plants to a different area in your yard, if possible.
On the other hand, if you are cultivating marijuana indoors, one of the first things that you need to check is the lighting. Intense lighting and putting your lamps too close to your plants can cause temperature issues. Additionally, you have to make sure that your grow room has good air circulation. Poor air circulation can prevent heat from dissipating in an indoor setup.
If your plants have been subjected to cold temperatures, the best thing to do is to move them to a warmer area.
- Light burn
Light burn occurs when grow lamps are placed too close to plants. Essentially, the heat emitted by grow lights can literally burn the plant leaves. Indoor plants are particularly vulnerable to this issue which can also cause leaves to turn yellow.
Signs to watch out for
With a light burn, the yellow leaves are mostly found in the areas that are exposed directly to the grow lamps. Another sign that a weed plant is suffering from this problem is that you cannot remove the yellow leaves easily.
What you can do
Light burn can be easily fixed by changing the position of your grow lamps. This will help prevent further damage. But aside from that, you should also check your grow lamp manufacturer’s recommendation on the optimal distance between your plants and their grow lamps.
- Leaf septoria
Leaf septoria is a type of fungal infection that affects different plant species, including cannabis. Although this infection can attack your plants at different growth stages, they are particularly vulnerable during the flowering stage.
Signs to watch out for
At the start of the infection, the weed leaves begin to develop dark spots. As the leaf septoria progresses, the marijuana leaves wilt and turn yellow. Left unchecked, leaf septoria can cause serious damage, stunting the growth of your plants and lowering their yield. Worse, the infection can kill your crops.
What you can do
Treatment for leaf septoria begins with trimming off the infected cannabis leaves. This will help prevent the infection from spreading to the other plant parts. Once you are done removing the infected leaves, apply neem oil to the remaining leaves.
Poor air circulation can contribute to leaf septoria. As such, it is highly recommended that you improve the ventilation in your grow space. Consider adding more fans and a dehumidifier. If you are cultivating weed outdoors, elevate your plant containers so that your crops can get more air.
Finally, remove dead leaves that may have fallen on the growing medium. These leaves may still carry spores that can infect your crops.
Can You Save a Cannabis Plant with Yellow Leaves?
That depends on the underlying cause of the yellow cannabis leaves and how fast you react to fix the issue. In most cases, there is no reason to panic and believe that you have lost all your efforts.
One important thing to remember is that whatever may be the reason for the yellow leaves, whether you are dealing with a nutrient deficiency, heat stress, or light burn, do not expect the affected leaves to turn green again. Generally, when marijuana leaves lose their green pigmentation and turn yellow, the plant abandons those leaves and absorbs the nutrients left which will then be channeled to the remaining healthy leaves. The only exception to that would be nutrient deficiencies where the leaves can turn green again when the cause of the problem has been solved.
Vigilance Is Key to Prevention
Any of the causes mentioned above can affect your crops. What is important is to keep your composure when you see yellow marijuana leaves so that you can pinpoint specifically the problem you are dealing with. And to prevent marijuana leaves turning yellow, it is a good idea to be vigilant and constantly monitor your plants so you can always stay on top of the situation.
