Why Your Leaves are Turning Yellow: Part 4

Today, we return to our series regarding the various reasons why the leaves on your cannabis plants might be turning yellow. We’ve already looked at causes such as over and under watering, bud rot, and nitrogen deficiencies. You could also have an infestation, or your pH might be off. What if it’s none of those? There are still other reasons why your plant’s leaves might be turning yellow.

Heat Stress or Cold Shock

Heat stress and/ or cold shock are both pretty common problems, especially among newer growers. Cannabis plants are pretty sturdy and can withstand, but they still need the proper growing environment. Your plants do the best if they’re between 70-75℉ and 50-60℉ in the light and dark respectively.

You’ll know that you have heat stress or cold shock if your lights are turning yellow and brown, as well as curling up at the edges like little taco shells. They’ll look like they are burnt on the edges a bit, which is a definite sign that they have been singed by your grow lights.

Your plants are more susceptible to cold shock if you have a sudden cold snap during the flowering phase, but you can avoid this as long as you keep the floors toasty! Heat stress happens when your plants are too hot, and is often the result of not watering enough and poor lighting practices, which you can fix by watering a little more and moving the lights slightly further away from the plants. Misters do a great job of cooling down your plants considerably.

iron deficiency leaves
This is a severe iron deficiency. Image Source: Reddit

Iron Deficiency

Iron deficiencies are not all that common, but you should still be aware of what they are. Cannabis plants require very little iron and most water sources contain plenty of iron. This problem is most common among growers using purified or reverse osmosis water, which does not contain iron of course.

This issue is very easy to spot because the effects are so unusual. Leaves come in completely yellow, and then start to turn green from the outside in. Newer and middle growth will come in yellow, but older leaves are not affected. The newer leaves tend to turn green as they grow older.

You can fix this by adjusting your pH, which you learned how to do in part 3. It is advised that you use a cal-mag supplement if using purified water, which compensates for the lack of natural nutrients.  

Now you should be very well informed on the reasons your leaves might be turning yellow.

For more in depth reading you can go here to download our Grow Bible for free!

Grow Bible

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  • Avoid common grow mistakes

    You can read parts 1,2 and 3 here.

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    Writer, Customer Support Angel at I Love Growing Marijuana

    Sarah is a D&D fanatic and loves singing silly songs to her cat. No matter what she does though, Sarah can always be found with a bong in hand. If there is one strain that she could call her favorite, that would be Zkittlez because it matches her colorful personality and hair!... [Read full bio]


    marijuana grow bible
    • Grow With My Quick Start Guide
    • Discover Secrets To Big Yields
    • Avoid Common Grow Mistakes