Sounds like old wiring to me. Sometimes sockets get loosened over time and when you put in the bulbs it twists on the wires.

Hi Ellenr,

It looks like your original light was an incandescent bulb and you replaced it with a compact fluorescent(CFL) which is a good idea regardless of your issues. CooperDR makes a good point, you could test the old bulb in another lamp. Finding one rated for 75w probably wouldn't be to hard for a short term test. Also keep in mind, incandescent lights are fragile and don't last very long, you could have a bad bulb.

While I don't always believe the "equivalent" ratings, the CFl is likely much more suited to growing than any incandescent light(including grow lights). There are a couple reasons the light meter might show a lesser value:

1. The meter picks up a specific wave length(s) of light. That spectrum could make up a lesser % of the light output from the CFL as the incandescent, so it seems weaker to the meter.

2. Fluorescent lights emit more diffuse light. The intensity goes down quickly as you move away from the light. The incandescent has a reflective coating so it concentrates the light in to a smaller area which is were you put the meter. I.E. all the light is coming out of the front of the bulb, where the CFL is emitting light in all directions.

I don't know what your growing setup is like, but you should use the CFL differently. Since they are much cooler you can put them very close to the plant, ie 1-3 inches. You can't do that with an incandescent since they throw off a lot of heat. I think your plant(s) will be much happier under the CFL. Just put it as close as possible to the plant.

Just a few minor points, most of which I'm sure you know. But some may not, so...

All light diminishes by the square of the distance regardless of type of bulb. Directed/reflected light can be more intense light as there is more going in the direction. Lighting fixtures suggest a certain maximum watt bulb, but those are geared to incandescents. It is the wiring but also the socket that determines that. So you can "over watt equivalent" most lighting fixtures with fluorescents or LEDS. I have no experience with halogens.

Reflected light is not all it is hyped up to be. The light frequency is slowed down toward the red or even infrared (like sunlight reflected off polar ice). You can use that, but you need a bluer source light for balance when using reflected light.

Personally, I use full spectrum 4' fluorescent bulbs and daylight bulbs mixed in the same fixtures. Odd as it may sound, I let my mesclun lettuces grow right up into the lights. It doesn't seem to harm them in the least.

But I AM watching this forum to learn more.

I have a low wattage full-spectrum bulb that I'm trying. Also a 60 watt plant bulb that I don't use because it gets too hot. I was told the 14 watt full-spectrum bulb wouldn't get plants to flower but it would work for microgreens.

to follow-up - I am still using the CFL, and my plants are happy.
They might be happier with a fluorescent set-up, BUT, they are doing well, and I am satisfied.

Things are growing and even Sage, which at first looked like it was gonna die, is thriving. Rosemary likewise.