Growing Basil under 450nm LED
Summary:
Grew basil under a 50W LED at 450nm, at a distance of about 15 cm. Growth was markedly inferior to plants grown on a window ledge in the September BC sun.Problem:
Apparently blue wavelengths are optimal for promoting leafy growth, centered at around 430 nm.Apparatus:
A bit of searching on Aliexpress turned up this 50W LED and matching driver at 450nm.It came without instructions, but it wasn't hard to figure out the polarity of the terminals.
The driver is rated for 30-34V, but only made about 28V. It was still insanely bright, but got hot enough to melt the solder off after about 2 minutes. Obviously it needed a heat sink. That got me thinking about how to safely assemble the whole thing.
A 4.5" device box is just the thing to contain the driver. It's fireproof, and it's already got 1/2" knockouts.
The driver didn't have mounting holes for standoffs, and this was a quick-and-dirty experiment, so I just made some clips out of strapping and screwed it onto a scrap of plywood. I needed a buck power supply to generate 12V for the heat sink fan, but fortunately there was still enough room on the plywood.
Light intensity wasn't very high relative to sunlight, so I put the LED about 10cm above the basil. The basil seemed to be browning a little after a week, possibly from excess IR, so I raised it 5cm.
Experiment:
I ran the LED on a lamp timer for 14 hours per day, for two weeks, on a tray of four recently propagated basil plants, watered with capillary ceramic watering spikes.My control was two more cuttings from the same batch, placed on a south-facing kitchen window ledge, getting most of the day's late-september sun.
Results:
I didn't do any rigorous measurement, and one of the LED plants died.The control basil had almost twice as much growth as the LED basil.
Conclusion:
The basil mostly didn't die, but wasn't very happy under the monochromatic light.
I should try another experiment in deep winter, doing actual growth measurements, and comparing against both the (very poor) BC winter sunlight, and a full-spectrum T5 grow light.
