What 'Full Spectrum' Actually Means on an LED Grow Light
By The Budometry TeamPublished Updated
Every light on the market says full spectrum. The phrase is not regulated, so it tells you almost nothing on its own. Two numbers matter more: intensity and efficacy.
Part of our pillar guide: Cannabis Grow Lights: Sizing, Height and Schedules
Color temperature in practice
3000K boards run warmer and are slightly flower-leaning. 4000K is more balanced and often used for veg. Mixed 3000K/4000K boards with a few deep-red diodes cover the whole grow well enough that most home growers never need to change fixtures.
Far red and UV
Far red can accelerate the transition to darkness and marginally stretch plants. UV-A/UV-B supplementation is popular for terpene and trichome response, with mixed evidence. Neither is required for a good harvest, and both add cost and risk.
What actually matters
Total PPF delivered to your canopy, even coverage across the footprint, efficacy in µmol/J, and a reliable dimmable driver. Get those right and spectrum arguments become a rounding error.
Frequently asked questions
- Do I need separate veg and flower lights?
- No. A single dimmable full-spectrum fixture run at lower power in veg and full power in flower is the standard home-grow setup.
The full guide on this topic
Cannabis Grow Lights: Sizing, Height and Schedules
How to size an LED to your tent, set hanging height by stage, run 18/6 and 12/12 on a timer, and hit the PPFD and DLI numbers that actually grow flower.