Cantripping: True it's a fairly common question and one you can find the answers to in a lot of resources. My experience has seriously led me to believe the color or frequency of the light is much more important than the wattage applied when you're talking about fluorescent lighting. I just finished three beautiful ladies who will keep my sugar bowl full for the next couple of months and they were grown from seed sprouting to harvest under T-5's. I planted the seeds in Rapid Rooter cubes in a sectioned 10" by 20" black plastic starter tray. After 24 hours of damp darkness I started them under four 5,000K blue grow tubes in a 14" wide by 2' long fixture in my little 2' by 4' by 6 1/2' tent. Each of the four T-5 tubes, 2' long, only draw 35 watts so they were under a total of 140 watts of lighting.
I transplanted them into 8" Eco Grow Pots filled with a mixture of Miracle Grow potting soil with an added amendment of 20%, (By volume), Perlite on top of a 2" layer of Vermiculite. I transplanted them when they were about three inches tall. They continued to grow and veg under blue 5,000K T-5 lamps in a fixture 4' long on a progressive lighting schedule that started at 20 hours on and 4 hours off at planting and it reduced the light by one hour each week.
At about 14 hours of light and 10 hours of darkness they started showing signs of pre-flowering and I swapped out the T-5 tubes for 2,700K red flowering lamps and changed the nutes I was using from a high N formula to a lower N formula that was higher in P and K. I kept dropping the light to 10 hours of light and 14 hours of darkness until harvest. The 4' long T-5 tubes only draw 55 watts each so the total draw on those three ladies from the four tubes was only 220 watts per hour. Hardly noticeable on my electric bill.
Lighting is a very complex subject but some people try to make it a lot more complicated than it needs to be. First, you need to understand how they measure the light that you're using for what you want to do with your plants. Im not an electrician and I certainly don't have all the answers but I'll try to simplify it for you.
Wattage is the load rating of a lamp or the amount of current or electricity that the lamp draws or uses. As I recall from a Physics class I took in the mid 70's, but don't hold me to it now because I don't have the book in front of me: Watts is amperage draw times the supplied voltage, and it's usually read in a relatively small number. CFLs typically draw:14, 17, 21, 29 watts. Incandescent light bulbs draw: 40, 60, 100, and MH and HPS draw: 250, 400, 600, up to a 1,000 watts. What that means is that the higher the wattage rating on the lamp the more electricity it uses and the more it costs to operate.
That's what got us all into all those little curly-cue CFL's, (compact fluorescent lamps), and they dropped my electric bill drastically on a level pay plan to a point where I don't even get a bill from the power company for three months of the year. Before my incandescent lights were burning 60 watts each, now theyre using only 14. It makes sense.
The really tricky part of this is that they advertise the wattage of electricity they use and the amount of light they produce and compare it to the equivalent used by an incandescent lamp putting out the same amount of light. The ones I just bought claim they only draw 14 watts but they put out the same amount of light as a sixty watts incandescent light bulb. The one I use on my clone mother draws only 29 watts but claims to put out the equivalent light of a 100 watt incandescent bulb. Now is that clear to you, or are you just as confused as the rest of us? But we're not done yet.
Lumens is a measurement of the amount light, the intensity it projects, the brightness and that's usually measured in hundreds of lumens. I don't know where the top of the scale is but the new brighter, Ecosmart CFL lamps I just changed over to in my home advertise that they generate 850 lumens of light while consuming only 14 watts of electricity. Now you don't have to light a match to find the damned things at night when they're turned on like their earlier predecessors. My wife used to bitch that the old ones being too dim to read under but now she complains that the new ones are too bright. Go figure. Now let's consider the color of the light they're producing.
Color, frequency or temperature of the light it produces is measured when it's run through a prism and seen in the available spectrum of colors. Its measured in Kelvins; K's. These new lamps I bought are rated at 4,800K's, which is pretty close to the 5,000K green T-5 grow lamps I use in my tent for vegging. The lower the K's, the redder and the warmer the light. The higher the K's the cooler the light and the color goes from green to blue. Cool, green to blue light is for vegetative growth and warm red light is for flowering. Got that? If you can keep that straight think about what the sun produces during the year. In the spring and early summer the light is bright and cool, it has a higher K rating number; it's greener toward blue and our plants grow. If you have a copy of Cervantess MARIJUANA HORTICULTURE THE INDOOR/OUTDOOR MEDICAL GROWERS BIBLE, look at page 160. Grow lamps are green to blue and that's the cool light thats suitable for vegging. Come fall we get those beautiful warm red orange sunsets and the light is red and warm and thats the 2,700K red light we use for flowering.
Now lets look at the practical side of this. Im going to fool my plants with the right diet and lighting to go from seed sprouting to harvest in half the time they will normally need in nature. From seed sprouting through vegging I feed my babies a high N diet thats low P and K to go along with the 5,000K grow lights and the longer lights on schedule. Right now I'm using 5,000K T-5 grow lamps for my plants to veg under. I'm told this is a moderately green light they like for growth and photosynthesis. One grower uses 6,000K's lamps and another grower uses 6,500K's. I was warned against the higher K rating by a person I trust at the hydro store. The other lamps cost a little more but my friend at the hydro store claimed he sees less light related problems with the 5,000K's so that's what I bought, and they've worked fine for me. Most people have these on for vegging anywhere from 24 to 20 to 16 hours a day. You choose.
When my plants begin to preflower I change their diet to a lower N and higher P-K nutrient blend and the lamps in their T-5 fixture to warm red flowering lights that are rated at only 2,700K. I also drop the light interval, (the time that they're on). Some folks go directly to a 12/12 schedule but I use a progressive light schedule that starts at 20 hours of light at seed planting with 4 hours of resting darkness and I reduce the light by one hour a week. But that's another issue altogether, and I explained it here already in another post.
After some experimentation I settled on a progression to a bottom figure of 10 hours of light and 14 hours of darkness and stayed with that until harvest. And the strains I'm growing seemed to really like it.
So if you're asking elementary lighting questions I suggest you RTFB. Refer to the following sources: 1. Read: SeeMoreBuds book, MARIJUANA BUDS FOR LESS GROW 8 OZ. OF BUDS FOR LESS THAN $100. 2. Read: Jorge Cervantess book, MARIJUANA HORTICULTURE THE INDOOR/OUTDOOR MEDICAL GROWERS BIBLE. 3. Read: Ed Rosenthals, MARIJUANA GROWERS HANDBOOK. 4. Read: Mc Carthys book, GROWING MARIJUANA. 5. Youll also want to subscribe to, HIGH TIMES, magazine. Each issue is chocked full of useful information. . All these resources are very well written, well illustrated and packed with information that will answer most of your questions before you know to ask them. 6. There's another excellent book I'm reading right now by Greg Green called, THE CANNABIS GROW BIBLE-SECOND EDITION, its every bit as good as the ones I mentioned above but a lot more technical. All of these resources are available at major book stores and at most growing forums. They will save you and your plants a lot of stress. The only problem with these forums is that if you get in a jam and need help right away it may be a while before we can get back to you. I sincerely hope this helps. HSA
