Light stress is another culprit. Your plant can get too much light (think leaf bleaching, yellow patches) or too little (stretchy, pale growth). Cannabis is a sun-worshipper, but even it has limits. If your leaves look like they’ve been sunburned at the beach, back the light off a bit. Conversely, if they’re turning yellow and dropping off, they might be begging for more hours of light. (Yes, plants can be divas.)
Temperature swings? Oh boy. Cannabis hates cold feet and hot heads. If temps drop below 60°F (15°C) at night, leaves yellow and curl. If it’s above 85°F (29°C), they scorch. Your plant wants a cozy, stable environment—like a spa, not a sauna.
Pests and Other Invisible Horrors
Let’s not forget the tiny invaders. Spider mites, aphids, and thrips suck the life out of leaves, leaving them speckled and yellow. You’ll know if you see webbing or tiny dots crawling around—it’s like a horror movie in miniature. Organic neem oil is your friend here, or a good rinse with water. (And please, don’t use harsh chemicals unless you want your buds tasting like a lab accident.)
Sometimes, it’s just old age—especially during late flowering. The lower leaves naturally yellow and die off because the plant is focusing all energy on those sticky buds. It’s the circle of life, but if the top leaves join the party, there’s a problem.
How to Diagnose Cannabis Plants with Yellow Leaves | Cafe420
