Blue and red light is most readily absorbed by plants, blue in particular for leaves. The cooler bulb here will have more blue and the warmer one more red. It probably doesn't make too much difference where the colour temperatures are so close together.
Perhaps your best bet is to have a blue bulb (and possibly also a red bulb) instead?
The difference between these bulbs is much smaller than most people think. Both have more red than blue light, but the 6500K bulb will have more light in the blue range than the 4000k bulb. Go with the 6500K for vegging. It's the ideal wavelength.
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Blue and red light is most readily absorbed by plants, blue in particular for leaves. The cooler bulb here will have more blue and the warmer one more red. It probably doesn't make too much difference where the colour temperatures are so close together.
Perhaps your best bet is to have a blue bulb (and possibly also a red bulb) instead?
Blue is more for growing, red for flowering, but of course it's the hours of light per day that will make the most difference
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.
The difference between these bulbs is much smaller than most people think. Both have more red than blue light, but the 6500K bulb will have more light in the blue range than the 4000k bulb. Go with the 6500K for vegging. It's the ideal wavelength.