Bear in mind that the bulk of the cost of providing artificial light, even using expensive tubes like the GroLux, is the electricity use. So if you wish to use GroLux tubes because you feel they are at least as effective as the best alternative, then knock yourself out and get them cheap. On the other hand if you feel they are less effective than the same power of some other type of fluorescent tube, then even a free GroLux would be a waste of money.

I imagine it is being discontinued because it isn't selling well enough. Very likely the availability of T5 straight tubes and high power compact fluorescents producing the same spectrum has killed the market for the relatively low power (and short-lived and expensive) GroLux T12s. LED technology is also now available to anyone who wants to use blue and red light tailored to the peak photosynthetic absorption wavelengths, and the LED output can be much more accurately tailored than the GroLux spectrum.

I will offer the suggestion that the Grolux "purple" spectrum is not radically better or worse than white spectrums. Most of the marketing claims for it are based on half-truths and exaggerations. Very likely it performs well in some situations, not so well in others. Studies have been done to show both results.

im pretty sure right now i got 2 sylnania one cool white and one warm, they might be growlux though, and im growing cucumbers, there pretty big, just waiting for spring to come so that they are ahead of the game, i got a watermelon also growing, all hydropincally, i have a 8bulb t5ho too but dont see the point of that dont want them to grow to big too soon.

You'd know if you had a GroLux, they don't produce white light by any stretch of the imagination. Bordello pink/purple and not very bright to your eyes.

To the person that said the Sylvania Gro-Lux bulbs do not actually work. HAVE YOU EVEN TRIED THEM? WHERE IS THIS INFORMATION YOU ARE GETTING THAT SAYS THEY DO NOT WORK?

You really should back up your statement if you are going to throw out such a judgemental remark. Do you even know if they work or not or are you just trying to bash Sylvania products? Do you really think a company that is renown in making light bulbs would put out a bulb for growing if it was complete b.s.?? It's these type of people that make me not enjoy being part of forums. Now to answer the originally poster's question. YES, THESE BULBS DO WORK BECAUSE THEY HAVE THE PROPER PEAKS IN THE LIGHT SPECTRUM THAT PRODUCE PHOTOSYNTHESIS AND BETA-CARATENES A AND B. PEOPLE, PLANTS DO NOT USE WHITE LIGHT. THEY USE BLUE AND RED MAINLY WITH A LITTLE GREEN, UV-A,B AND INFRA-RED. GO BACK TO SCHOOL!!!!!!!!!!!

I have an inside 10 plant drip system using expanded clay, I am having a go a growing Bok Choy under 2 x Sylvania Grow Lux 48' tubes. My Hydroponic supplier told me today that I have the incorrect light source and that these are only good for seedlings. This has me a little disapointed as I thought these would be sufficient ,My set up is beside a window , on the other side of this window I have another outside grow system so I am getting both diffused lighting both outside lighting and the two Grolux tubes over my plants inside.I live in Brisbane Queensland Australia where we are sub tropical and have excellant sun light hours both winter and summer. Any one who is growing successfully under these similar circumstances I would love to hear from you.
Bob