It occurs to me that I have even more questions to add to my first post. The light fixtures I have can handle a max of 60 W incandescent bulbs. So I suppose I am not limited to buying 60 W equivalent CFLs am I? As long as the higher wattage CFL's will fit in the reflectors, I could go to 100W (equiv) bulbs. Does anyone have a guideline for the amount of lumens/plant to make supplemental lighting worthwhile, or is such a thing possible?

The blue end of the spectrum (cool whites) favors development of foliage, usually the most important consideration in maintaining tree health over winter. The red end favors development of flowers and fruit (warm white). You can decide which is more important, but you will definitely be able to retain better o/a vitality by choosing cool white.

Temperature and accompanying danger of fire is what limits wattage ratings for light fixtures. Since temperature is of little consideration with fluorescent lighting, you can feel comfortable exceeding wattage limitations for incandescent bulbs (note that you're only exceeding an imaginary number as wattage ratings are only a tool for comparison. Actual wattage usage is much lower than the comparative incandescent rating)

I don't know if the guideline you asked about exists, as "worthwhile" is a pretty subjective term. Any supplemental indoor lighting is going to be helpful to varying degrees. Incandescent is prolly least helpful as it would need to be very close to plants for them to benefit - impossible because of the heat associated with their use. The effectiveness of the fluorescents, of course, varies with light source proximity to plant photosynthesizing surfaces.

Al

Al, thank you for your very helpful response. I am having trouble finding bulbs labelled "cool white". I can find "day light", "bright white", "warm white", and "soft white". Can you give me the appropriate light ranges in k (kelvin?) for "cool" and "warm" white? Some of the packages include this data. I think I will try 2 "cool" and 1 "warm" in each fixture.

Thanks again!

Annie

The Kelvin scale is a scale like Celsius & Fahrenheit that is used to assign a value to temperature. A change of one degree Kelvin is approximately the equivalent of 1* change on the Celsius scale. However, the Kelvin scale starts at absolute zero, which is around -275* C, or -460* F.. Nothing you'll prolly ever need to concern yourself with btw, and I haven't used it in days. ;o) lolol

See some data @ the link I provided if you choose. I buy the bulbs in 10-packs @ Home Depot. They're "Cool White Plus" and offer 3200 initial lumens. (Can also be purchased individually.)

Here is a link that might be useful: ... and he said,

It was difficult to find cool white CFL's! I had to settle for some labelled "daylight", and 90 equivalent-watts was the most I could find. The "K" data I was referring too isn't kelvin, as in temperature, but a measurement of the color of the light emitted. The daylight bulbs I purchased are labelled 5500-6000k. So now each of my fixtures have one warm white and two cool white. I hope my plants appreciate all the running around I did to find lamps and bulbs for them ; -) Thank you for your help.

In case anyone else is curious about supplementing light for indoor citrus with CFL's, I thought I would report back after my first winter doing so. It was a great success. My three citrus: persian lime, meyer lemon, and minneola tangelo thrived through the winter. Despite the cool room temps (55 degrees on average), the plants put out new growth, leaves, flowers and fruit during the coldest, darkest months. My plants will be in great shape when they go outdoors in May. This is a marked contrast to last year, when my meyer defoliated in protest after being moved indoors in the fall and stayed that way until late spring and the other plants basically did nothing for months. The lighting was inexpensive by virtue of being CFL bulbs mounted in tree-style fixtures that were $18 at Home Depot. The only challenge continues to be finding "cool" white CFL's. It is easy to find cool white shop tubes, but cool is not a light color popular for indoor lighting so finding it in CFL's has been a challenge for me. If anyone knows of a source, I'd love to hear about it so I can stock up for next winter.