I'd sure like to know since they are cheap and specialty lights for growing are not.

HPS is HPS, so you can use the ones sold as yard lights on your plants. Some plants will stretch if they are grown only under HPS, otherwise it is the most efficient plant light for large areas. Unfortunately low power versions are not so efficient. A 50W HPS puts out no more light than a good fluorescent of the same power, so you would generally choose the fluorescent for its more even spectrum.

As for herbal plants, I'm not really qualified to comment. And apparently the people who are qualified are too out of it to reply to your question ;)

I have a greenhouse and our winters in Oregon are grey and misty like those in the UK. I wish to keep my tropicals alive and blooming if possible.

The local greenhouse/hydroponic supply store wants over $400 for a 400 watt HPS system. I just can't afford that. The security lights are about $50 and I figured DH could rig a reflector of some sort.

No herbals in my greenhouse. Did grow them in the greenhouse in high school in 1980. Boy was the horticulture teacher mad....

You'll need about ten security lights to equal the 400W light, cost $500 ;) HPS are ideal for supplementing natural light but one security light isn't going to do squat in a greenhouse. Realistically, even the 400W light would only be sufficient for a small greenhouse, say up to about 6'x8'. Blooming might need twice as much light. Plus you'll notice it on your utility bill when you start using lights twelve hours a day, every day.

You can buy 400W floodlights online for about $200. They require a little wiring which an electrician can cheaply do.

But the electricity is the greater expense. At 16 hours per day, they cost about $30/month to run.

HPS is good for all stages of herbal growth. However, morphogenesis of earlier stages benefits with some blue spectrum in it. HTG Garden supply has good deals on
HPS systems, $119 including the ballast, lamp and reflector.
Much, much better than a puny 50W lamp which will do almost nothing in a greenhouse. Please note that I do not grow herbs, but am primarily interested in roses, which however is
also a high light requiring plant, and it has the bonus of being non-photoperiodic, and benefits from lights being on 24/7.

Here is a link that might be useful: HTG Supply

My greenhouse is a puny 6 x 8.

My plants are tropical waterlilies, jasmine, gardenias, mandevilla, hibiscus, taro, papyrus and a few assorted tropical "house" plants.

I will check out HTG Supply. Thanks

Wow, that is a great price. Is that company and the brand of light reputable?

Is 400 watts enough for a 6 x 8 greenhouse?

I make a purchase from HTG 2 years ago. They sent the wrong lamp, but when I pointed it out they sent the correct one with no problems. I guess if they are still in business, they are probably reputable. I would suggest asking them to upgrade the lamp from the utility one to a reflectorized lamp (Gavita
style), and delete the reflector supplied with their package deal, and what price they would be willing to sell for. That
would be my plan, actually that might even be my plan. I have an indoor garden and I need strong illumination for my roses.

Here is a link that might be useful: Gavita style 400w reflectorized lamp.

Oh, and whether 400W is enough for a 6 x 8 greenhouse, I would consider going for a 600w hps. There is also a 600w reflector
Gavita style lamp available that just pours out the lumens, more lumens per watt using that strategy. I'm thinking of doing that as well myself.
However, I really don't know if 400w hps is sufficient as supplemental light for a greenhouse, as I really do not have experience there, only with growing exclusively with HID.

Here is a link that might be useful: 600w hps ballast

I am new to growing so I am going to start with herbs. I am purchasing a 125 CFL with a reflector ballast for some of my herbs. I am going to purchase a 400W HPS system from HTG later. THanks.

I got my 400w hps light from htg they seem to be a great company it was around $119 and shipping was fast 3 or 4 days if your in a hurry but i still have warm weather hear so it's killin me to just put it on a shelf and wait i'm using it in a smaller area 3x5 to keep my garden alive this winter