Lights recommended by Moonshadows (Jim):
https://happyleafled.com/produ...
Lights recommended by Dave:
https://www.amazon.com/dp/B08VJ4X2QL/
Lights that I am using (starting in early 2023):
https://www.amazon.com/dp/B0BPN7LXG5/
These lights performed very well for me in 2023, growing nice stocky seedlings and later (late fall/early winter) I grew half a dozen "Red Robin" tomato plants under them and the plants flowered and set fruit enthusiastically. I'm planning to grow more indoor plants in the winter of 2024 and will probably purchase more lights since I need the original 6 fixtures for starting seeds from February-June.
from PSA:
I start ~10,000 plants every spring under highbay fixtures with mirror reflectors and six T-8 daylight bulbs each across an 18" x 4' fixture. The larger number of bulbs reduces the drop off in light over distance, so I don't have to move them as the seedlings grow.
When I buy bulbs I look up the spectral curves for contractor boxes of T-8 bulbs and match them to the PAR charts to get an adjusted light output rating. I used to do the mixed color bulb thing, but I found that the drop off in PAR (which is the amount of light that's available for the plants to use) dropped off too rapidly with most bulbs to make a difference. Mostly I just buy the bulbs with the color temperature spectrum that I need for vegetative growth, which is on the blue side.
When I do need to induce blooming or something, I add red supplementation. I think the T-8 bulbs are the best bang for the buck right now, and the ballasts that are available today are far more efficient, even in the lowliest shoplights. Whatever you do, make sure you have daylights in the mix.
from drdawg:
There has been a lot of research that identifies which plants need what sort of light (wavelengths) and intensity to germinate, grow, and flower. Generally speaking, plants utilize two sorts of light and for discussion I will call them "red" and "blue." The wavelengths between the red and blue peaks of the spectrum are more what our eyes see. This "visible" wavelength is something like 430-660 nanometers. At the extremes are UV and infrared, and neither of these is beneficial to plants. An overabundance can cause plant mutation and even death. UV is less than 400 nm and infrared greater than 700 nm. Excess UV mutates cells. Excess infrared burns plants. (For orchid growers and many other tropical plant growers, this infrared is what "sunburns" our plant's leaves.)
The so-called "visible" light, the range that our eyes can actually see, is not really beneficial to plant growth/bloom. That means that the vast majority of incandescent lighting won't help you much.
Most plants need a good measure of both red and blue spectrums. The useful blue is 400-450 nm and the useful red is 650-700 nm. These numbers become important IF you want to use some sort of Gro-Light.
For spring and summer bloomers, during the fall our light will move gradually from the red spectrum to the blue spectrum. I'm talking about the Northern Hemisphere. As the sun gets lower in our southern sky, the blue spectrum increases. The blue triggers the plants to "change gears" from growing (vegetative) to blooming (budding). For fall/winter bloomers, just the opposite occurs. During the spring/summer, as the sun moves more overhead, there is more of the red spectrum and this triggers the plants to bloom in the fall/winter.
From RickCorey: https://www.amazon.com/dp/B0BPN7LXG5/
