Training & Plant Architecture
Defoliation Objectives & Tradeoffs
Removing leaves changes photosynthetic area, airflow, light penetration, and source-sink relationships at the same time. Defoliation should therefore have a defined objective and measured response rather than being treated as a universal schedule.
Key concepts
- Leaves are photosynthetic source tissues
- Removing selected leaves can change local light and airflow
- Heavy removal can reduce available photosynthetic area
- The response depends on plant vigor, developmental stage, and how much tissue is removed
What to measure or observe
- Record which leaves and how much tissue are removed
- Map light before and after
- Observe recovery and new leaf expansion
- Compare flower-zone humidity or airflow where that is the objective
Common mistakes
- Removing leaves only because a calendar says to
- Calling every large fan leaf unproductive
- Changing defoliation intensity between experimental groups
- Attributing later crop differences to defoliation without controlling other variables
Visuals this lesson still needs
- Leaf source-area diagram
- Selective-versus-heavy defoliation comparison
- Before-after PPFD map
- Recovery observation timeline