Marijuana leaves change shape and color throughout the grow cycle, but how can you tell if what you’re seeing is normal or a cause for concern?
We’re here to help you with the vital task of keeping track of your plant’s health by observing the weed leaves.
Our simple, comprehensive guide walks you through all the main cannabis leaf problems that growers experience and breaks down what to do in each case.
So let’s get started with some basic botany.
Why marijuana leaves are important
Your marijuana plant leaves are like the dashboard in your car. If you pay attention to them, they’ll let you know if something is going wrong with your cannabis plant.
Identifying the problem is the first step to finding a solution.
Some of the most common signs of problems that you’d see in your leaves are:
- Wilting marijuana leaves
- Yellow marijuana leaves
- Curly marijuana leaves
- Other color marijuana leave changes
What do cannabis leaves do?
Cannabis leaves allow your plants to convert light into energy through photosynthesis. They contain a nutrient called chlorophyll that can absorb light and store the energy contained within. Chlorophyll is what gives weed leaves their green color.
Marijuana leaves also act as the lungs of the plant. Tiny holes, or stomata, on the underside of the weed leaves take in carbon dioxide and give out oxygen and water. The plant then draws on the energy stored in chlorophyll to turn the inhaled carbon dioxide into sugar, which it uses for energy.
turning yellow
This is a central process in marijuana plant anatomy and shows why it’s critical to maintain healthy marijuana leaves.
Though cannabis plants get most of their nutrients through the roots, marijuana leaves can also directly absorb nutrients. This is known as foliar feeding and is useful to remember as it’s one of the best ways to restore a struggling plant’s health quickly.
What are fan and sugar leaves?
Fan and sugar are two different types of marijuana leaves you can find on your plants.
The iconic marijuana leaf known worldwide, the fan, is imprinted onto everything from grinders to bed sheets. A sugar leaf is a smaller type, found closer to the bud and covered in frosty-looking, THC-containing trichomes.
Fan leaves
Fan leaves are bigger and are the most important in terms of the photosynthesis process. Their larger surface area enables them to absorb a lot of light, which aids in photosynthesis.
Like a camel’s humps, fan weed leaves can also store nutrients such as nitrogen for when there’s a shortage in its environment.
If your plant starts using the stored nitrogen in its leaves, your cannabis leaves will start turning yellow. We cover what you need to do in this case later.
Fan leaves only contain trace amounts of THC, CBD, and the other active ingredients in weed, so people don’t usually smoke them.
Sugar leaves
These marijuana leaves are much smaller than fan leaves and look like they have been coated in sugar. They don’t do much photosynthesis—instead, they provide support for the buds, holding them in place.
Though sugar leaves contain more trichomes than fan leaves, they are rarely smoked due to their harsh, planty flavor.
Still, resourceful gardeners have found creative uses for both types of marijuana leaves.
How to spot cannabis plant health issues through the leaves
Keeping an eye on your marijuana plants’ leaves to monitor the overall health of your plants is crucial. If your cannabis leaves are curling up or down, wilting, or turning yellow, then you should take action to restore the health of your plants.
An unhealthy plant will yield a smaller or no harvest. Understanding weed leaves is one of the things to know before you start growing marijuana.
Why do cannabis leaves wilt?
One of the most common cannabis leaf problems is wilting leaves. This could be caused by:
- Underwatering
- Plant diseases
Underwatering
If your plant is drooping and the leaves are wilting, then you probably aren’t watering your plants frequently enough. Water your plants more often to prevent your leaves from drying out and your plant dying.
Plant diseases
Plant diseases like verticillium and fusarium wilt are rarer causes of wilting cannabis leaves, but they’re more challenging to solve. These diseases are caused by fungi that live in the soil.
The marijuana leaves will look like a plant that has been underwatered, as the fungi block water from moving around the plant. A tell-tale sign of a wilting disease is that a whole plant may droop suddenly.
In this case, it’s best to avoid the issue before it arises. Make sure you use fresh soil or even consider using hydroponic methods instead.
If your crop has already been affected by a wilting disease, you need to remove any plants that have drooping marijuana leaves immediately. You should also remove the soil surrounding those plants.
What could cause yellow weed leaves?
Yellow cannabis leaves are a warning sign that your plant isn’t doing well—unless you are in the flowering stage of your grow, in which case it’s normal and nothing to worry about.
Reasons your cannabis leaves could be turning yellow include:
- Overwatering
- Nutrient deficiencies
- Nutrient burn
- Plant diseases and pests
Overwatering
When plants are overwatered, marijuana leaves can turn yellow . This is the easiest problem to fix as long as the issue is just excess water. Water your plants less often and let the soil dry out between waterings. Your cannabis leaves will quickly return to health.
You should also ensure that your pots are draining thoroughly as this may result in root rot.
Though the issue of too much water is easy to solve in most cases, it’s more difficult if overwatering has allowed fungi to thrive. Many variations can make your cannabis leaves turn yellow.
Since many love heat and moisture, ensure that you aren’t providing a comfortable environment for fungi to avoid more complicated cannabis leaf problems.
Nutrient deficiencies
Your cannabis plants need the right amount of nutrients to grow healthily. Marijuana leaves turn yellow if they can’t get enough nitrogen from their environment, a problem known as nitrogen deficiency.
Cannabis deficiencies can also be caused by a lack of phosphorus, sulfur, iron, calcium, zinc, etc. Solving this problem may be as easy as giving your plants more plant food.
If your weed leaves are yellow because of a nutrient deficiency, foliar feeding (feeding your plants nutrients through the leaves) is particularly useful. This is because it allows you to treat individual plants displaying symptoms of poor health.
Foliar feeding is also brilliant for dealing with phosphorus, iron, and zinc deficiencies. Phosphorus can sometimes change chemically in the soil to a state that plants can’t absorb. Iron and zinc tend to be scarce in general. Feeding these nutrients directly through marijuana leaves can ensure the plant has everything it needs.
Unfortunately, the problem of yellow weed leaves caused by nutrient deficiency isn’t always as simple as feeding your plants more often. Sometimes it’s caused by a pH imbalance in the soil around your plants, meaning the soil is too acidic or too alkaline.
Cannabis plants absorb nutrients most effectively when the pH level of the soil is between six and seven. Plants find it difficult to absorb nutrients if the pH levels of the soil are outside this range. Your cannabis leaves will start to change color quickly if the pH level of your soil isn’t right.
For hydroponic or coco growers, the ideal pH level of non-soil mediums is lower, between 5.5 and 6.5.
Overfertilisation A.K.A. nutrient burn
Another complicating factor here is that overfertilization, i.e., too many nutrients, can also lead to cannabis leaves turning yellow. This is often known as nutrient burn, and it’s one of the most common mistakes made by new marijuana growers.
If only the tips of your marijuana leaves turn yellow or brown, nutrient burn is likely the issue. You can prevent it by making sure you don’t overfeed your plants.
Plants that have been overfed need to be flushed to remove the excess nutrients from the surrounding soil. Once you have flushed your plants reduce the amount of fertilizer you use to a more appropriate level.
Plant diseases and pests
Several plant diseases and pests can also cause yellow marijuana leaves.
Root rot and bud rot are particularly annoying issues as the cannabis leaves may not turn yellow until the situation has become unsalvageable.
Root and bud rot is linked to overwatering, poor drainage, high temperature, and high humidity as the fungi thrives in these conditions. It’s best to make sure you’re not drowning your plants.
Cannabis leaves that have yellow spots, or leaf septoria, are another condition caused by a fungus. Again, prevention is better than cure.
The marijuana leaves that have yellow spots need to be pruned quickly as the yellow spot contains a spore that you want to get rid of to stop the problem from spreading. Separate the infected plants from the rest of your grow and improve the air circulation in your grow space.
Fungi love heat and moisture, so monitor the color of your weed leaves, as well as the temperature and humidity in your grow space. To prevent any of the cannabis leaf problems caused by fungi discussed in this article, you may want to consider using fungicides.
Pests like spider mites can also cause yellow cannabis leaves, but in this case, the discoloration will look like tiny yellow speckles. You can prevent the infestation from going further by increasing the airflow in your grow-space to stop the spiders from reproducing.
Ultimately, you should use insecticide to get rid of them permanently.
Why do cannabis leaves curl or dry out?
Another common cannabis leaf problem is cannabis leaves curling, which is also known as clawing.
There are many potential causes for this, including:
- Overwatering
- Heat stress
- Cold stress
- Windburn
Overwatering
If you’ve overwatered your plant, your cannabis leaves may be curling down and turning yellow. Don’t water your plants as frequently and give the soil around the plants the chance to dry out.
Heat and cold stress
If your plants are too hot or too cold, your marijuana leaves will be curling up. They’ll also most likely be drier and crispier than healthy leaves.
Heat stress, or light burn, is a very common problem with indoor grows as the weed leaves are often too close to the grow lights. Try to move your plants further away or consider using lights that emit less heat, such as LED lights.
If you’re growing outdoors in a hot climate, make sure your marijuana plants’ leaves are protected from the sun.
You can mitigate cold stress by using more powerful lights when growing indoors. Better insulation can also help keep your grow space’s temperature at a suitable level, around 28°C with the lights on.
Those growing outside in cold temperatures should consider using cold-resistant strains.
Windburn<
Windburn is most likely to cause cannabis leaves curling up for outdoor growers in an unsheltered space. This is easily remedied by providing shelter for your plants, such as a windbreaker or grow tent. Any physical barrier that reduces the exposure of your plants to the wind is fine.
Indoor windburn is caused by fans being too close to your plants; simply move the fan or the plants further away.
Other reasons for weed leaf color changes
Most of the time, changes in the color of your weed leaves are normal and maybe even beneficial. Most green, purple, red, pink, and yellow shades can all be natural, healthy colors for your cannabis leaves, so there’s usually no need to worry.
Two cases where there may be an issue are if your marijuana leaves have turned very dark green or if they are turning white.
Very dark green weed leaves indicate a kind of nutrient burn where the underlying issue is too much nitrogen during the flowering stage. Remember that different stages of the growing cycle require different mixes of nutrients.
White weed leaves are either very good or very bad. If the leaves are crystally because they’re loaded with trichomes, you have hit the jackpot. If the white substance is more powdery, then it could be another fungus. As with the fungi discussed above, you should remove the infected plants and the soil.
What can you use cannabis leaves for?
As they are too harsh to smoke, many growers have found alternative uses for their weed leaves. Sugar leaves are great for making cannabutter or hash as they carry many cannabinoids that would be a shame to waste.
Fan leaves carry fewer cannabinoids, but you can put them in a compost pile to help your next grow. Some people recommend making tea or other products from these marijuana leaves, but the amount of THC they contain is so small that this perhaps takes more time than it’s worth.
Cannabis leaves FAQ
Can you eat cannabis leaves, and are they healthy?
Yes, and yes. Marijuana leaves are edible for humans, and they contain nutrients. Human nutrition is still quite poorly understood, but scientists increasingly believe that eating a diverse range of plants is vital for a healthy stomach, which is vital for a healthy brain.
Scientists advise eating 30 different plant-based foods every week.
Why do cannabis leaves droop at night?
Drooping marijuana leaves at night is completely normal. The cannabis plants are just reacting to the amount of light around them. They’re essentially sleeping, and the leaves droop as the plant relaxes.
Are cannabis leaves safe for cats and dogs?
Pet-owning weed smokers may say yes, but scientists tend to say no. Since marijuana leaves don’t contain huge amounts of THC, they wouldn’t have a huge effect, but we recommend staying on the safe side.
