Why are my lower cannabis leaves turning yellow during pre-flower?Updated 13 hours ago

Seeing lower leaves turn yellow just as your plants begin to stretch can be concerning — especially when everything else looks healthy. This is a common issue, and there are a few likely causes depending on your setup.

🍂 1. Natural Leaf Shedding

As plants transition into flower, they may begin to shed some older fan leaves — especially the ones lower down and shaded from light. If yellowing is isolated to the bottom few leaves and the rest of the plant looks vigorous, this may be part of a normal metabolic shift.

🧪 2. Nitrogen Deficiency

Cannabis needs less nitrogen in flower, but not none at all. If yellowing is rapid and spreading upward, your plant may be drawing nitrogen from lower leaves to fuel new growth.

What to do:

• Apply a balanced feeding with a mild nitrogen component.

• Many growers shift to a bloom nutrient around this time, but make sure it isn’t completely devoid of nitrogen early on.

🌿 3. Nutrient Lockout or Imbalance

If you’re already feeding and yellowing still appears, nutrients might not be getting absorbed properly due to:

• pH imbalance (target 6.0–7.0 in soil)

• Salt buildup from overfeeding or dry soil cycles

• Overwatering limiting oxygen at the roots

Try this:

• Check runoff pH and EC if possible

• Ensure you're not overwatering or letting pots dry out too completely

• Consider a gentle flush if you suspect buildup

🌱 4. Environmental Stress

Heat, low humidity, or poor airflow can all put stress on lower leaves. During stretch, the plant’s energy is focused upward — older growth can suffer if the microclimate at the base is too harsh or stagnant.

✅ Quick tips:

• Don’t panic if just a few bottom leaves are fading — that’s often normal.

• Focus on the overall plant health and new growth.

• If yellowing is spreading, act quickly with a balanced, flower-ready feeding plan and pH check.

Still unsure? Reach out with your setup details and we’re happy to help you troubleshoot. 🌿