Cool white vs red-blue grow lights for seedlings
Oklahoma State says to use cool white light for seedlings, and that red and blue lights are meant for mature fruiting plants.
What the sources say
- Oklahoma State: use "cool white" light for seedlings. Red and blue lights are meant for mature fruiting plants.
- Iowa State: a full-spectrum bulb gives enough red and blue light for seedling growth at a lower cost than a purple-looking grow light.
- University of Illinois: use both cool (blue) and warm (red) tubes for a broader spectrum, or buy plant-specific grow lights, which cost more.
What this means when you shop
- A white light listed as 5000K or similar daylight white fits the cool white and full-spectrum descriptions above. See the gear shortlist for published examples.
- Pink or purple fixtures cost more according to Iowa State and Illinois, and the sources do not say they are needed for seedlings.
- Brightness and distance matter more than colour. See shop lights for seedlings and hanging height.
The sources reviewed do not compare 5000K with 6500K directly, so we do not recommend one over the other.
Sources
- Oklahoma State University Extension: Tips for starting seeds at home (2025)
- Iowa State University Extension: What type of lights should I use to start seedlings indoors?
- University of Illinois Extension: Starting the garden, supplemental lighting for indoor seed starting (2020)