Yellow leaves on the lower part of a cannabis plant most often mean a mobile nutrient deficiency, especially nitrogen, or pH drift that locks nutrients out of reach. Mobile nutrients move from old growth to new growth, so bottom leaves fade first while the top stays green. Test pH and runoff before adding anything.
cannabis yellow leaves lower plant
Why do lower cannabis leaves turn yellow first?
Nitrogen, magnesium, potassium, and phosphorus are mobile nutrients. When supply runs short, the plant pulls them from older fan leaves and sends them to fresh buds and shoots. That is why lower leaves yellow, curl, or drop while the canopy above looks healthy.
cannabis yellowing leaves causes
What deficiency causes yellow lower leaves?
Nitrogen deficiency
Uniform pale yellow that starts at the bottom and moves up is the classic nitrogen sign. Leaves may feel soft and stems can turn reddish. A nitrogen-rich feed at the right pH usually stops the spread within days.
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Magnesium deficiency
Magnesium yellowing shows as interveinal chlorosis, where veins stay green and the tissue between them fades. It also begins low on the plant. Epsom salt or a calmag supplement often corrects it.
Potassium deficiency
Potassium shortage yellows and browns leaf edges, again starting lower. It is common in late flower when plants demand more K. Check your bloom nutrient ratio.
Could pH or overwatering be the cause?
Nutrients can be present but unavailable if root-zone pH sits outside 6.0 to 7.0 in soil or 5.5 to 6.5 in coco and hydro. Overwatering and poor drainage damage roots, which then cannot absorb food. Soggy soil plus yellow lower leaves usually means root stress, not hunger.
How do you fix yellowing lower leaves?
- Measure pH of your feed and runoff.
- Check watering frequency and pot drainage.
- Feed a balanced or nitrogen-forward nutrient at the correct strength.
- Remove fully dead leaves so they do not invite mold.
- Wait three to five days and watch new growth.
When should you worry about yellow lower leaves?
Some yellowing is normal late in flower as the plant finishes and fades. It is a problem when yellowing climbs fast, hits middle or upper leaves, or comes with spots, curling, and stalled growth. Fix the root cause early, because damaged leaves do not turn green again.