Plan lighting for seedlings and herbs
Seedling and herb grow-light planner
Build a grow-light schedule aimed at seedlings or culinary herbs.
Get a light-height and runtime starting point
Choose seedling or herb stage, then see a cautious starting height and daily schedule.
How to use this estimate
Choose growth stage and tray setup for a cautious height and runtime starting point. Watch for stretching risk and uneven edge coverage — not a plant-health diagnosis.
Common mistakes
- Keeping lights too far and encouraging stretch
- Leaving edge cells chronically under-lit
- Skipping a dark rest period overnight
- Using general houseplant categories for seedlings
Assumptions at a glance
Last reviewed with the calculator formula set on 2026-07-23. Estimates stay range-based on purpose.
Key sources and methodology details
- Daily Light Integral from PPFD and photoperiod — University of New Hampshire Extension. Reviewed 2026-07-26. https://extension.unh.edu/resource/supplemental-lighting-run-time-worksheet
- Indoor plant light category DLI planning ranges — University of New Hampshire Extension (synthesized planning bands). Reviewed 2026-07-26. https://extension.unh.edu/blog/2021/02/optimizing-plant-growth-indoor-lighting-qa
- Transplant / seedling DLI example guidance — University of New Hampshire Extension. Reviewed 2026-07-26. https://extension.unh.edu/resource/growing-seedlings-under-lights-fact-sheet
Full portfolio methodology: Methodology
