Posted on November 04, 2010
LED Grow Lights - Lumens vs PAR Test (Ongoing)
Before we begin, please answer the following question:
Which light do you would think is the best for growing plants that fruit or flower?
1. A full spectrum light (warm white) with very high Lumen output.
2. A light with low Lumen output but high PAR output(when compared to light #1).
Although this is a loaded question that is hard to answer, most people would choose 1. For the past twenty years HID(HPS and Metal Halide) lights have been the main workhorse for so many indoor growers and the high Lumen output has been the benchmark for measuring a lights potential. If you are growing plants that fruit or flower you really need high light intensity but not high Lumens, just high PAR. I know this may seem shocking but our latest tests have proven this.
We tested two lights against each other, the first light was our control light using our 180w Extreme Flower LED grow light, the second was the same as the 180w except the entire light was built from extremely high output white LEDs from Bridgelux. This test light used all 3w LEDs and was tested for both Lumens and PAR against the control light. The tests showed that the test light had 500% more Lumen output(comparable to HIDs) than the control light but the control showed a surprising 130% higher PAR output than the high Lumen test light.
Although light meter tests can be helpful they are nothing compared to a true grow test. In our grow test we used the same wattage, same growing medium, same plant strain, same temperature etc. We started the plants in two different grow tents side-by-side and kept all the conditions the same including light time. During the first few days of the seeds sprouting the high Lumen lights seem to win out over the Extreme Flower LEDs as the sprouts grew taller and began to set leaves slightly faster. Again for the first leaf sets it looked as though the high lumen light might actually beat the control light due to slightly faster vegetative growth and taller plants. At week two the high lumen light was taller than the control light but the number of leaf sets was the same and the internodal spacing was beginning to stretch. At week three it became obvious that the control light plants, although shorter, were much more dense and had a higher growth rate than the high lumen light. The internodal spacing on the control light was tight and the leaf sets were seperating extremely fast with lush vegetation. The high lumen light showed signs of stretching and less branching, with an overall growth rate that seems to be less than the control light so far.
This test is still ongoing with but the Extreme Flower LED Grow Light(control light) is showing fast dense growth. So far the test is showing that higher Lumen output is not a good indicator of plant growth potential. It would seem to indicate that proper color output(high PAR output) mixed with high light intensity leads to the dense plant growth many indoor growers are looking for.
We will update this grow test with flowering data and yields as they become available.