Why Are My Cannabis Leaves Turning Yellow?

Normal yellowing vs. a real problem

Some yellowing is expected. Lower fan leaves naturally senesce during flowering as the plant redirects energy to buds. A few yellow leaves at the bottom in week 6 of flower is usually fine.

Worry when yellowing spreads rapidly, affects new growth at the top, or appears with spotting, curling, or wilting. The pattern and speed tell you more than the color alone.

Watch how to diagnose yellow leaves

See common yellowing patterns up close — then use the breakdown below to match what you're seeing on your plants.

Nitrogen deficiency

Classic nitrogen deficiency starts on older, lower leaves and moves upward. Leaves turn pale yellow, then brown, and drop. Common in late flower (expected) and during veg if under-fed.

Overwatering

Overwatered plants often show yellowing with drooping, clawed leaves and heavy, soggy soil. Roots need oxygen; waterlogged medium suffocates them and mimics nutrient deficiency.

Fix: let the pot dry out until the top inch is dry, improve drainage, and ensure pots have airflow underneath.

pH lockout

When pH drifts out of range, nutrients sit in the medium but roots can't absorb them. You'll see mixed deficiency symptoms — yellowing, brown spots, purple stems — despite feeding correctly.

Always check runoff pH before adding more nutrients. Adjusting pH often fixes 'mystery' yellowing within days.

Quick diagnosis table

Match the pattern to narrow your search:

• Lower leaves, pale yellow → nitrogen deficiency or natural senescence
• Yellow between veins, green veins → iron or magnesium (check pH first)
• Yellow tips with brown edges → nutrient burn or light stress
• Whole plant yellow, drooping → overwatering or root rot
• Upper new growth yellow → sulfur, calcium, or severe pH issue