Deficiencies in cannabis plants can show up in a variety of ways but most commonly you’ll start to see symptoms on a cannabis leaf.
The interesting thing about cannabis is that it’ll usually tell you what’s happening by where the leaves start to change. This is incredibly important when it comes to diagnosing what’s going on with your plant.
There are two general types of nutrients, immobile and mobile. Mobile nutrients are the main macronutrients such as nitrogen. This means that the plant will take nutrients from other parts of the plant (generally older leaves) to supplement the newer leaves before any permanent damage happens.
Immobile nutrients like calcium and iron can’t be moved from other parts of the plant so you’ll start to see issues happening in the newer growth.
If the newer growth is starting to turn yellow that is a general indicator that you are having an imbalance with an immobile nutrient such as calcium and iron. This narrows down your search for what’s causing the problem and can help you rectify the issue quickly.
Keep in mind that yellow leaves are technically called chlorosis (meaning can’t perform photosynthesis). Now that you know what causes the new growth to turn yellow on your cannabis plants, let’s take a deeper look into the potential problems you could be facing.
Causes Of Yellow Leaves In New Cannabis Growth
Here is a shortlist of what issues you’ll need to address if you are seeing your fan leaves turn yellow at the top of your cannabis plant.
Calcium is pretty much the building block of your cannabis cell structure. Without calcium, you will have plants that cannot support the weight of the large buds you’ll be producing. This is an easier one to spot because the top growth will become stunted and yellow as there is no calcium to promote healthy growth.
Your leaves will also look distorted and curl a bit at the tips. Eventually, it will migrate and affect the lower leaves, effectively starting to kill the plant.
You will seldom see a sulfur deficiency in your cannabis plants because they don’t require much at all. Sulfur is a semi-mobile nutrient which is why you’ll start seeing chlorosis at the top and in the middle of the plant. Your cannabis plant uses sulfur to build a strong and healthy root system.
If you have a sulfur deficiency don’t immediately go and add a sulfur pot to your room.
This deficiency is usually caused by an issue with your PH which causes nutrient lockout, or the inability to absorb specific nutrients. Sulfur deficiencies are also commonly confused with nitrogen issues in your plant.
Even though iron is considered a trace element in cannabis plants, it plays a vital role in creating the green pigment that absorbs light to be converted through photosynthesis.
This is a trickier deficiency to identify as it can be mistaken for almost any other deficiency affecting the top leaves.
The easiest way to identify this deficiency is to look at the newest growth and the growth right under it. If the leaves are yellow but the veins stay green, it is an indicator of an iron deficiency.
If you’ve identified a nutrient issue and you’ve thrown excess of that nutrient at it and your problem is growing, well, it may not be the nutrient that’s the issue. Incorrectly balanced PH can cause nutrient lockout which basically disables the plant from absorbing any nutrient that is affected by PH.
This is much more common than issues with trace nutrients as cannabis can get those from the ground or the water you feed it.
All that’s required is a flush with PH corrected water and a rebalancing of the nutrients in your feeding regimen. This should help clear up any issues.