Which Type for Indoor Gardening
I went out to purchase some new fluorescent lights and found a bewildering array of types to choose from.
Grow lights, daylight types etc. all at a bewildering array of prices. I’ve usually used regular cool whites, which are by far the cheapest and will do a good job of germinating seeds and growing the seedlings.
I took some cuttings from my Geraniums,(Pelargonium cvs) in late summer and was planning to overwinter them. I planned to take some more cuttings from them midwinter to increase my crop. In order to do this well, I decided to try some of the other types of fluorescent lights and started to read the fine print. I admit to being easily confused but choosing fluorescent tubes to grow plants under ??? Of course they market “plant and aquarium” types but they were $5 - $8 per tube. (All of the types and prices etc here are for standard 48" T12 tubes.) Cool white, the common standard was typically $2.
The small print on the back of the sleeves usually gave some basic information. Lumens 1600 - 3300, being the actual quantity of light emitted. Colour temperature ranged from 3100K to 6500K and is a measure of the yellowness or blue/whiteness of the light. The higher the number the bluer the light. These are the two items that varied and seem to really matter. When growing plants we are using light as an energy source. It would seem that the more light a tube produced, lumens, the more the plant would receive.
All of the specified “plant lights” had the lowest number of lumens, about 1800. The typical cool white tube puts out about 3200 lumens. This struck me as a bit counter-intuitive! Both the plant light and the cool whites were rated at colour temperature of 4100K. The marketing on the front of the fluorescent lights packages indicated that the "plant lights" put out a different spectrum with more infrared light that was supposed to make the plants look and grow better. It would have to be a lot better for 2 - 3 times the price. I passed on all the plant lights.
There were daylight tubes that produced around 3100 lumens, almost as much as the cool white but had a bluer colour temperature at 6500K. They were $3 -$4. I bought some of them and they make the plants look good and certainly my Geraniums have been thriving, even flowering well, under them. I will try to do a comparison between the daylight types and the cool white types but it will have to be quite subjective as I certainly don’t have the equipment to do any realistic measure of the amount of growth achieved.
Natural light at $9 - 2200 lumen and soft white at $6 - 3300 lumen and sunshine at $7 - 2250 lumen, only served to confuse me further. When confused I stop looking. My plants seem to be happy and so is my budget.
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