Mixed spectrum Lighting

slimakJune 28, 2013

Is mixing T5HO bulbs with different spectrum beneficial to plant growth? I read on another forum that some are using aquatic type bulbs in different combinations to veg and flower. I don't remember the exact bulb names but one of them was the Red Sun(which puts out 633nm) for example. Has anyone tried that for vegetable growing?
Second question is are UV lamps beneficial in any way to a vegetable plant?

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Most good quality fluorescent is of the tri-phosphour type meaning it has 3 different phosphour types that have complementary emission sprectrum - blue, yellow/green, and red. The color temperature tells you the balance of the spectrum - for example a 5000 K lamp has more blue than red, and a 3000 K lamp has more red than blue. Visit the Ushio website and they show the spectral output of the different lamps. So there is completely no need at all to mix lamps, because the lamp already is a mix. I personally like 5000K although 4100K also is fine. Blue light is required for synthesis of chlorophyll, but even a 3000K has blue in it, just not that much. UV lamp is no good - it will give you cataracts, just to start, so stay away!!! A visit to the Ushio website will answer all the rest of you questions.

    Bookmark   July 1, 2013 at 7:27PM
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Do you recommend any particular bulb brands and models that go into far red spectrum? I do understand that the spectrum output is different for different brands with same kelvin value.
I'm mainly looking for the best T5HO bulb for flowering

    Bookmark   July 2, 2013 at 1:28PM
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the lamp brand does not matter - phosphour is a basic commodity that comes from a mining operation, and the brand of the lamp does not matter. I buy according to price, lumens, lamp life, and color temperature. For example a 5000 K lamp will have a very similar spectrum no matter who makes it. If you are looking for more reds, then use a 3000 K lamp, but my initial enthusiasm for reds was not matched by the real life experience, so I just use either 4100 K or 5000 K. For best "flowering", and I have also grown roses for flowers, peppers for flowers, and even cannabis for flowers, and despite what some people or websites claim as "flowering spectrum", my experience is that there is really no such thing, and the plant is very well adapted to using any kind of photon it can get for its energy - some plants are photoperiodic meaning they need a certain length of night time darkness to trigger flowering, and some can be triggered by far red (730 nm) wavelength light, that is not really available from any commercial means that I am aware of, but do not worry, the plant will flower no matter what color of temperature, and will do equally well with 4100K as compared to anything else. This has already been studied for many years, and I have not seen any valid literature to the contrary. So just buy a 4100K lamp according to price/lumens/longevity, on the triphorphour type, and there will be no problem. The main problem that I see is INSUFFICIENT light, not light of the wrong "spectrum".

    Bookmark   July 2, 2013 at 4:08PM
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I see what you're saying. I'm trying to understand the theory now and since I'm new to this that's why I'm asking for someone who actually experienced different spectrum bulbs. I'm aware that plants will grow either way but I just want to see what is the most productive way to grow plants under T5 HO lights from start to finish.
The information in the link below confused the heck out of me :) because from what I understand is that spectral irradiance and spectrum wavelength emitted is most important when talking about what plants care about and not Lumens since they are units related to human visual needs. So when you say INSUFFICIENT light which unit of measure are you talking about?

If you mean lumens, how many lumens do you believe will be satisfactory per square foot to grow fruit plants using T5HOs?

Thank you again


    Bookmark   July 2, 2013 at 5:07PM
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obviously plants use PAR - the problem is manufacturer of lamps is doing it for human use, and so they display the lumens. I have found, in my own experience, that high lumens, with a tri phosphour lamp give the highest PAR. An expensive "full spectrum" is good for artists and grocery stores etc., but this "full spectrum" lamp supplies far less PAR, so don't waste your money (I already did that for you). So as far as what you need to know in terms of buying, is lumens. Of course we want to have more knowledge, because we are naturally curious, and always look for the best way, etc., and that is fine. I have bought the full spectrum pulse start Metal Halide by Venture such as the 575W, and in this case (only this case) the full spectrum actually does supply more PAR. Also the pulse start technology is very high tech and latest. However, fluorescent lamps are old technology, and basically what I said at the start is still true.

The link you gave does not work.

Roughly around 30 watts of lighting per square foot is a good rule of thumb. You can also buy a cheap light meter for around $20 which will measure your light to give you a rough idea. Having a meter is a good idea, even if it does not read in PAR, so you can easily compare your new lamps to what you were using before, and for an objective measure. The compare with how your plants are growing etc.

Like I said, this is all interesting discussion, but from practical point of view, I pack in as many lamps as I can per square foot, and use a ballast that gives the highest current per lamp that I can find. This means that I use cheap shop lights, throw out the ballast, and replace it with a better ballast that is easy to find used on ebay. I also use the technique of "overdriving" fluorescent lamp. The T5 lamp you are using is "overdriven" by design - however you can run a T8 lamp with higher current ("overdrive" it) and it will put out similar light to a T5 or even more, with less initial outlay of money for similar results. Personally I don't get why T5 is even used, except for possibly the government is looking for less drain on the electric grid - however for home growing T8 is perfect - (meaning cheaper and just as good).

So I have been investigating this topic for many years, and it all boils down to the same - get the cheapest lamp that gives highest lumens, and make sure it is triphosphour.

As for the question about lumens per square foot, don't worry about that, just go by watts/ square foot. It used to be with T12 (which are horrible) 40 watts per square foot was needed. With better technology T8 and T5, 30 watts per square foot is good, and that's all there is to it - very simply put.
I sometimes use more that 30 w / square foot, up to 40 w per square foot, but that depends on what i'm growing - e.g. if the plant is getting quite tall, versus shorter plants etc. With taller plants, like 2 foot tomato seedlings growing in 2 gallon grow bags, higher lighting works better. In that case I would use HID lighting because fluorescent it just too weak for very tall plants. Anything over about 12" and you need to think about HID. So it depends what you're growing. For cannabis I would also prefer to go higher, but only if you are certain there is no problem with LEO.

    Bookmark   July 3, 2013 at 3:10PM
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Sorry about the link, it should be


Ok so I should be ok for now, I got about 54w per square foot. I'll have to make it work somehow with the T5's because I'm concerned about potential fire with HIDs, can't deal with the fan noise that I would have to keep those systems cool. Also don't have too much space to implement different photoperiod zones by having separate tents with HIDs. I plan to grow different vegetable plants at the same time so that simply won't work.

I'm trying to maximize the effectiveness of those T5s by using reflectors and the orca film( I'm not sure if you heard of it) but besides that is there anything else that I could do to make it work with fluorescents ?

I came across an interesting lecture about photoperiodism and plant hormones. Are you trying to control plants by pruning to change the hormone ratios to make the plants flower sooner?


Once again thank you for your help

    Bookmark   July 3, 2013 at 5:59PM
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the forum messes up the link, just delete the space between h and tm at the end

    Bookmark   July 3, 2013 at 6:07PM
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