Why we have veg and flower lights

Discussion in 'Lighting' started by Swami, Jul 21, 2011.

  1. #1 Swami, Jul 21, 2011
    Last edited by a moderator: Jul 23, 2011
    'Blue for veg; red for flower'

    There appears to be widespread misunderstanding on this issue, so let's see if we can clear this up.

    First off let us remember there is only ONE SUN. We do not have two suns. Does the solar spectrum change from spring to fall? Of course the sun itself does not change according to earth's seasons, but what of atmospheric filtering? The changes are so small as to be ignored.

    So the obvious answer is that with at least one light source, two different spectra are not necessary for plants to germinate, grow and fruit.

    Well then, how and why did the two light system come about? HPS spectra is less than optimal, but it has the highest photon flux density of any man-made light source (plasma may have recently surpassed HPS).

    1. Seedlings and young plants do not need the blast of light that HPS provides, so why waste power when a lower wattage light (CFL, T5, MH) is more than adequate?

    2. Cannabis needs adequate blue light to prevent stretching and for optimal leaf growth. HPS is generally very weak in blue, thus an alternate source is chosen for the vegetation stage. MH and fluoro both have sufficient blue to meet a young plant's needs.

    Does more blue equal more vegetative growth and more red equal better flowering? No, if the minumum is met more is not better. For example if 20% blue keeps the internodes short during veg, twice as much blue will not make even shorter nodes. In the same way increasing the amount of red required for flowering will not necessarily equal bigger flowers. The proper ratio is fine for the entire cycle.

    For example, the whole cool (bluish - not blue) CFL/T5 for veg; warm (redish - not red) for flower is total myth. Warm fluoros contain plenty of blue to meet all of the plants vegetative needs and can keep them short as is evidenced by this beauty vegged under a single warm 2700K 23w CFL:


    So the answer is: If a man-made light is properly designed then only one lamp is necessary.
  2. Good call on the CFL/T5. Seems like it makes more sense to stick with just the redder bulbs for higher PAR/Watt. I wonder though -- what additional beneficial spectra are made available from mixing a 2700k fluoro and 6400k fluoro?

    A successful grower I spoke with swears by vegging under HPS and flowering under CMH. He reasons that HPS emits a simple spectrum that doesn't confuse the seedlings. The CMH has all the wavelengths that big plants crave. It doesn't fit with tradition but I don't argue because his results are stellar nonetheless.

    As far as photosynthesis goes, at the quantum level, one photon of red does as much work as one photon of any other color such as blue (assuming that the photon is of a correct wavelength to be absorbed at all). Therefore, if all other "trigger spectra" are at adequate levels, just increase the red for more photosynthesis because the red photon costs less electricity to produce than any other usable photon.

    I'd like to see a setup with HPS as the main light with horizontal T5 side lighting to add a blue containing spectrum right near the plants as they mature to optimize inter-nodal lengths and branching, then during flower to provide light to the lower bud-sites.
  3. I thought is was just cause during the planting season, the sun looks whiter, and during the harvest season, the sun looks more red/orange.

    That's some technical stuff up there ^ buddy.
  4. Note that all 2700K and 6400K are not alike, but as far as my knowledge extends, there is nothing to be gained. It is just a fallacious extension of the MH/HPS paradigm.

    If you checked out my photo, that plant is twice as wide as it is tall, done soley with 2700K. You can see that there is virtually no stretch whatsoever and the leaves are healthy, thus the plant is clearly getting sufficient blue. Do a search and check out some fluoro spectral graphs.

    On a tangent, I was able to get such good results using such a tiny 23w light is because it is focused and reflected near perfectly.
  5. Indeed! I have contacted the manufacturer of my 23W bulbs asking for a spectral graph of their product.
    I would be interested to see a picture of your reflector. Having just finished a section on conic sections as reflectors, the idea of designing one to optimum seems so doable. It would be a bit different as a CFL is not a point source as in the examples I went through. Through perhaps it is close enough. Should be fairly easy to model a reflector in blender and do simulated ray casting tests too. Just 23W on that plant? Good stuff!
  6. Bucket lamp1.jpg

    Bucket lamp2.jpg

    These are two versions of my 5 gallon Lowes bucket lamp. The first one uses Reflectix (way better than mylar and avaiable at most major hardware stores). The second one uses an inverted 1 or 2 quart plastic flower pot and white paint. If you use paint be sure to allow several weeks to cure or the fumes will harm your plant.

    The second one runs cooler because of better venting, but the light and growth is about the same for either. If one were to hang the lamp, the second one would be prefereable because it has a more focused beam.

    23-26w is about the limit with the venting I used. One could obviously make bigger holes or incorporate a PC fan, but the plant outgrows the bubble lamp with just a 23 watter.

    Basically I just flip it upside down over my 5 gallon bubble bucket and place on 1/2" by 1/2" wood sticks for an air gap. A 13w is fine for the first week or so.

    I created this because of grow room space limitations.
  7. I am also a scientist and an engineer so I appreciate your desire to optimize. However, because this is an enclosed rather than an open-air design, most all of the light, minus reflective and leakage losses, hits the plant. I am guessing roughly 85%.
  8. Yes, I see. Still, the reflective losses could be minimized. Probably wouldn't matter enough to fabricate something when a bucket suffices just fine -- gotta keep it KISS!
    Why do you prefer reflectix over mylar?
  9. Sturdier and easier to clean. Doesn't seem to get cloudy or tear easily like mylar does. More expensive though.

    With the Reflectix in the bucket, I just formed it in a cylinder and taped it. I can take it right out. Trying doing that with mylar.
  10. I am so glad I found this thread, the bucket light is genius, the fact you used a single cfl and have photos is great. I have so many ways to use this info in a great design.
    thanks alot!
  11. Not genius, but thanks! I think it is least two times as efficient as using a clip on reflector and perhaps three times as efficient as an open air CFL.

    I have two bubble buckets waiting for the flower room and have actually switched back to a 13 watter to slow the growth down as the plants are getting quite full. Its either that or rig a contraption to hold the bucket light up higher.

    For those not into DWC, I also find the bucket light perfect for starting seedlings.
  12. T o those who have no need of the bucket light in your grow room, the white plastic flower pot makes the best ghetto concentrator I have seen for CFLs. Forget soda can reflectors, there is no comparison.
  13. Swami, really appreciate your input on design and light spectrum. I am totally sucked into the MH/HPS thing right now. I started up a 250W MH Conversion bulb recently and could not believe the heat issues. I am flowering under a 110W HO FL light from HTG Supply. It is 24". I get some d3ecent results from it, but thought I would do better vegging with more intensity. After 4 weeks I use the 250W HPS I have. The plants usually really jump with the intensity and haven't done too bad, but not great either.

    If I stuck with this 250W set up, would you suggest one bulb to use? I have heard a 3000K is optimal for start to harvest. If I continue to have heat problems in my tent with the MH Conversion I will stick with the 110W fixture.

    Also, a question on your 5 gallon bubbler bucket. Is the plant down inside it or at the surface of these buckets? I am unfamiliar with them. Thanks.

  14. Bottom bucket with plant is right side up. Bucket lamp is upside down on top. You could drill vent holes around the rim, but I raise it 1/2" by putting two sticks crosswise for support on top of the bottom bucket. Don't want to get heat build-up in there.
  15. I have actually already copied the design, and my thought was to use it for the seedling stage. I have a wing-design of 6 cfl's for the next (veg) stage.

    By genius, I see genius in many things, it is better for me this way.
  16. My very first lamp design was 6 CFLS in row in a curved stainless steel (sideways 'C') ducting on a wood frame. Good idea; lousy results. First, the steel needed white paint as plain steel is a very poor reflector. Secondly, the light scattered all over the place as I had them pointed down instead of horizontal.

    In your wing design, use specular aluminum if you can afford it. Second best would be to use a roll of thin aluminum sheeting (used for flashing?)from your hardware and glue or screw it to your base . It comes in 6", 10" and 20" rolls. Third best is to use flat white paint.
  17. Would aluminum flashing really be more reflective than flat white paint?
    That bucket design really is genius. It's such a simple thing that anyone can do to veg a plant efficiently.
    I looked for reflectix at the hardware store. Found a big roll of reflictix insulation for 12usd. It's like mylar coated bubble wrap. Way cheaper than the 2mm mylar I was looking at buying. Good call.
  18. I cannot say for sure without testing. My second LED lamp I used white painted plywood as a reflector. As the LEDS are directional, reflecting is not as important as with other lights. I am certain the flashing would be better than paint if I were to use a rough wood substrate as I did, but a smooth metal or plastic surface is probably altogether different and may very well be superior.

    Does anyone here have a light meter to test with?

    Tonight I am going to start my first group of clones using a bubble bucket and bucket lamp. As I only have one air pump, I will borrow it for 30 minutes from my DWC bucket twice a day to keep the clones oxygenated. As the clones need humidity more than fresh air to start, I will not space the buckets. The clones will be pushed through the center of one of those 4 foot long pool floaty things cut into 1" lengths and floating on the suraface of a gallon or two of water. bulb will be the smallest I have, either a 9W CFL or a 15W incandescent.

  19. I agree.

    I agree with everything except the part about HPS not having enough blue. Imo modern horticultural HPS bulbs that are "blue enhanced" contain sufficient blue spectra to meet the needs of cannabis in all stages of plant growth.


    Another myth you could add would be that HPS is better because it induces flowering. I'm not sure where that came from, but I believe it's false. Cannabis flowering is triggered by the photoperiod, not light quality (spectrum).
  20. so I'm still slightly confused on 1 issue
    I have a dual 600 setup
    and 2 MH and 2 HPS bulbs which will be the most effective for my plants while I
    1- veg them
    2- flower them
    or should i keep 1 of each of the bulbs on the plants all the time so they get a mix of both light spectrum during veg. and flower????
    this has always been confusing and everyone I know has a different opinion on what is best

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