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[Shpongle Lover]

OK...so I hope this is the right section to ask or build a thread for this topic.  If not, mods please move.

I'd like to start a discussion on how many hours a day of light, what frequency of light, and what sources of lights people use for various plants.  What are YOU using, and why?  What have been your results?  I'm VERY confused as to what to set up for continued plant propagation in my two indoor greenhouses for this winter.  A visit to my local pet supply store showed the dizzying array of "Flora Sun", "Ultra Sun", etc (see pix) which tout "max plant growth" and others "super daylight".  Then there are the CFL's.

If I'm looking to propagate Perskiopsis, Loph seedlings,  P.viridis, and (hopefully if the seeds arrive) T. Iboga in my greenhouses, what would you recommend, and why?

Thanks!

S.L.

1 Like dEEcor likes this.

[Sunshine]

I give all my plants around 9-14 hours of light a day. I use 432 watt T5 4 foot 8 light 6500k blue spectrum fluorescent light setup. The light works excellent. It only cost me around 135$. In fact, I think it may be too strong for some of my smaller cacti as some of them have turned red and gotten 'sunburn' because the light is too strong.

Viridis doesn't need much light. The loph and pere need strong light. I'm not sure about T. Iboga.

Here is a link to the light I use- http://www.ebay.com/itm/290840163098

The ad says 1,144$ but I only paid 135$. I'm not sure why he relisted it so high.

I highly recommend you get something like this- http://www.ebay.com/itm/121047706431

[New Wisdom]

I use the same lighting as Sunshine.  Same fixture and stuff. Although I give my cacti 18 hours of light when they're indoors.  I try to keep them outdoors as long as I can, but winter always inevitably comes.

[Sunshine]

I almost forgot to add;

If you use a combination of 2 different spectrum lights together the overall lumens will be higher than if you only used 1 spectrum type of lighting. So if New Wisdom and I changed out every other 6500k light for 3200k or 2200k spectrum T5's then the overall lumens will be higher.

[Shpongle Lover]

I give all my plants around 9-14 hours of light a day. I use 432 watt T5 4 foot 8 light 6500k blue spectrum fluorescent light setup. The light works excellent. It only cost me around 135$. In fact, I think it may be too strong for some of my smaller cacti as some of them have turned red and gotten 'sunburn' because the light is too strong.

Viridis doesn't need much light. The loph and pere need strong light. I'm not sure about T. Iboga.

Here is a link to the light I use- http://www.ebay.com/itm/290840163098

The ad says 1,144$ but I only paid 135$. I'm not sure why he relisted it so high.

I highly recommend you get something like this- http://www.ebay.com/itm/121047706431

>$1,000.00?? That isn't happening!  Must be a typo.

The second listing was MUCH more to my liking.  I just bought TWO of them for under $250.00 with free shipping.  Two lesser light arrays will give me far greater flexibility anyway.  I'm thinking I'll mount them vertically along the sides of the greenhouses, giving even light on all four shelves.

I am seriously ignorant when it comes to understanding the meaning of the degrees kelvin of the light output.  Does that refer to a particular frequency/spectrum of the light?  Do the 6500k lights basically mimic daylight?  Cooler light temperatures (ex: 3200)...those are biased more towards the red, right?

S.L.

[Sunshine]

The kelvin measurements refers to the color, or spectrum of light. In the evening light moves towards the red spectrum and during the morning it is more towards the blue spectrum.

During the fall time it is more towards the red and in the spring it is more towards the blue because the tilt in the earths axis.
Blue spectrum is better for vegetative growth and red is better for flowering.

Low kelvin lights in the red spectrum can be used for flowering and high kelvin lights in the blue spectrum can be used for vegging. I have heard mixed results on the efficiency of both. Some people are adamant that red is best for flowering and blue is best for veg. Others think that it doesn't matter which is used.

In any case, a combination of both would be best so that the plant would have the broadest spectrum of light.

To recap, in a nutshell; Both the tilt in the earths axis and the rotation of the earth cause the light light we receive to either be elongated or compressed, which causes the light to look a different color, depending on the time of day as well as the time of year.

To answer your questions more directly;

Do the 6500k lights basically mimic daylight?

Yes, daylight in the morning and during springtime.

Cooler light temperatures (ex: 3200)...those are biased more towards the red, right?

Correct. But I think it would be easier to understand if you thought of the measurement in kelvin as a wavelength measurement and not as a temperature measurement.

1 Like dEEcor likes this.

[Shpongle Lover]

Remember when I asked you about your avatar?  I was, for the longest time, an avid amateur astronomer.  My only clue as to lights, wavelength/temperature I inferred from what I knew about stellar spectral classifications.

Stars are classified by their surface temperatures via observable absorption lines that can be seen only at a set temperature at which atomic energy levels for certain constituent stellar elements become apparent.

Example:
   
O   30,000 - 60,000 K    Blue stars
B    10,000 - 30,000 K    Blue-white stars
A    7,500 - 10,000 K    White stars
F    6,000 - 7,500 K    Yellow-white stars
G    5,000 - 6,000 K    Yellow stars (Our Sun)
K    3,500 - 5,000K    Yellow-orange stars
M    < 3,500 K    Red stars

It all kinda makes sense...or at least it is starting to.  I'll figure it out eventually.  In the meanwhile, I'm happy to follow your recommendation.  I'll report back on the receipt of the light banks when they get delivered.

S.L.

[Sunshine]

When you first plug them in and turn them on to test them, wear sunglasses. Lol

[Mandrake]

As Sunshine and New Wisdom suggested, T5 work good with a nice wide spectrum, are cheap and efficient. But if you can find T4, go for them. The smaller surface of the tubes improves efficiency, so you will get more lumens/sq. foot per watt of potency. But T5 are fine enough.

And I think a few corrections are needed, following thread order:

I almost forgot to add;

If you use a combination of 2 different spectrum lights together the overall lumens will be higher than if you only used 1 spectrum type of lighting. So if New Wisdom and I changed out every other 6500k light for 3200k or 2200k spectrum T5's then the overall lumens will be higher.

I'm afraid that's not true. Lumens and color temperature cannot be related like this. Color temperature is a measure of the quality of visible light, and lumens are a measure of luminous flux. Lumens depend on wattage and how efficient the lamp is - the less energy lost in heat dissipation, the more efficient. If you have two lamps with the same efficacy (lumens/watt) they will give the same amount of lumens, regardless of the color temperature they deliver.

It's true that combining lamps with different CTs, specially when compared to lamps with high CTs only, can deliver better results when growing indoors - but that has to do with the width of the light spectrum the plants are receiving, not with the amount of lumens.

The kelvin measurements refers to the color, or spectrum of light. In the evening light moves towards the red spectrum and during the morning it is more towards the blue spectrum. It is in this sense that light is very similar to sound. When moving away the wavelengths are elongated just as sound is when the object is moving away. In the later parts of the day the sun is moving away from us so the wavelengths stretch and appear as a more reddish color.

During the fall time it is more towards the red and in the spring it is more towards the blue because the tilt in the earths axis. (...)

To recap, in a nutshell; Both the tilt in the earths axis and the rotation of the earth cause the sun to vary in distance which causes the light we receive to either be elongated or compressed, which causes the light to look a different color, depending on the time of day as well as the time of year.

I know this is a side comment, but please let's not make bad science here... The color shift in dawn and dusk has nothing to do with the Doppler effect. In the later parts of the day the sun is definitely not moving away from us quick enough to make light color shift visibly. In order to get a shift in wavelength large enough to alter the sunlight color, the relative speed change would need to be huge. Besides the fact that "apparent" relative movements can prove to be quite different once you take into consideration not just rotation of earth, but translation around the sun.

The reason for the color shifts is in the atmosphere. Blue light (shorter wavelength) is more easily "filtered" or scattered by the gas and dust particles in the atmosphere, and when the sun rays have to cross a longer section of it (that is, at dawn and dusk) the higher part of the spectrum reaches less the surface, so we perceive more the lower-middle part of the spectrum. Those lower wavelengths colors look usually brighter at dusk due to the reflection of dust, debris and pollution more present in the atmosphere in the end of the day.

So the more perpendicular you receive the sunrays, the bluer you will see them (also due to our bigger eye sensitivity to blue, and not violet for instance) and also the dirtier or "thicker" the atmosphere, the "warmer" you will see the light.

Blue spectrum is better for vegetative growth and red is better for flowering.

Yes, this is the general opinion. So...

Low kelvin lights in the red spectrum can be used for vegetative growth and high kelvin lights in the blue spectrum can be used for flowering. I have heard mixed results on the efficiency of both. Some people are adamant that red is best for flowering and blue is best for veg. Others think that it doesn't matter which is used.

In any case, a combination of both would be best so that the plant would have the broadest spectrum of light.

As you implied in the previous quote, it's the other way around - low CT ("red") is often better for flowering, and high CT ("blue") is generally preferred for vegetation.

The best spectrum of light is mostly continuous (i.e. with not a lot of missing, relevant wavelengths, particularly in the red and blue ends) and closely related to the type of lamp you're using. In the case of fluorescents, it depends on the gas and the coating of the tube, but it's generally good enough. If you're using a lamp that has a limited spectrum, particularly if important ranges are missing, combining will be a good idea. But using cool white fluorescents (usually around 4000K) I've found that other types of lamps are hardly necessary.

And just to leave the technical definition for color temperature of a light source, it's the temperature an ideal "black body" (i.e. an incandescent lamp) would have when radiating light with a hue comparable to the light source.

Kind regards,

Mandrake

[Sunshine]

Low kelvin lights in the red spectrum can be used for vegetative growth and high kelvin lights in the blue spectrum can be used for flowering. I have heard mixed results on the efficiency of both. Some people are adamant that red is best for flowering and blue is best for veg. Others think that it doesn't matter which is used.

I misspoke. I meant that red spectrum is better for flowering and blue better for veging.

I'm afraid that's not true. Lumens and color temperature cannot be related like this.

I think they are actually.

On another note, regarding redshift. Thanks for correcting me. I was mistaken. In any case, the light will be redder at dusk and during the fall. My reasoning was just off. *shrugs*
I edited out the misinformation as to not confuse anyone.

And just to leave the technical definition for color temperature of a light source, it's the temperature an ideal "black body" (i.e. an incandescent lamp) would have when radiating light with a hue comparable to the light source.

Can you elaborate on this?

[Mandrake]

I'm afraid that's not true. Lumens and color temperature cannot be related like this.

I think they are actually.

The fact these T5 lamps show in their specs a higher efficacy in the 2900K lamp (93,5 lumen/watt) than in the 6500K lamp (88 lumen/watt) does not mean that lumens and color temperature always show a mathematical relation. This simply means that, in these Quantum T5 bulbs, the performance in 2900K lamps is better due to the components of the lamp, either the materials, the digital ballast, or both. But again,

If you use a combination of 2 different spectrum lights together the overall lumens will be higher than if you only used 1 spectrum type of lighting. 

This is not true as a rule. CT and lumens are completely different values, one of them is qualitative, the other is quantitative. If you measure the light output at the same distance, some lamps with the same wattage and different CTs may show different lumen output, or the same, but that is due to the efficiency of the lamp/ballast fixture, not to the color temperature.

To quote the video you shared (3:08) "of course there's going to be more lumens in the middle than right in the end. That's where the lights are converging". The measure of lumens depends on wattage, efficiency and distance, not CT. The particular features of the T5 lamps you use are exactly that - particular features. According to your T5 lamp specs, if you used only eight 2900K lamps, and no 6500K lamps at all, you would get more lumens than if you combined four of each.

If you want to read further about lumens and CT, this is a good introductory forum post.

And just to leave the technical definition for color temperature of a light source, it's the temperature an ideal "black body" (i.e. an incandescent lamp) would have when radiating light with a hue comparable to the light source.

Can you elaborate on this?

Sure. Color temperature is used to indicate the hue of a light source. The reason why "temperature" is used, instead of some other parameter, has to do with experiments carried out by Lord Kelvin in the XIX century. He heated a block of carbon (which behaves in physics as an ideal "black body", virtually the same as for instance an incandescent lamp filament for subjective purposes) and observed that, at different temperatures, the carbon would emit different hues of light. At first it would be a dim red, becoming yellow, and eventually producing a bright blue/white at the highest temperatures. So we use Kelvin degrees to describe color temperatures in his memory. They are qualitative (subjective, relative) measurements that describe the color hue of a light source. For instance, a light sold as "5000K" emits a quality of light equivalent to the light that a piece of carbon would produce when heated at 5000 Kelvin degrees.

Kind regards,

Mandrake

[Shpongle Lover]

If you want to read further about lumens and CT, this is a good introductory forum post.

Wow...I got a LOT out of that "introductory(!)" article.  Thanks, Mandrake.  That answered a lot of my questions.  +1 for you, sir!

So...now it comes down to variables such as artificial "length of day" lighting.  What works "best" for general growth, and (drum roll for my million dollar question) what lighting conditions do I need to provide to induce flowering in Lophs and other cacti???  I've owned SO MANY cacti for so many years, and not once have they produced a flower based on natural light from our window sills.   

What the heck do I need to do to get them to flower???  Maybe its the light period, maybe something else I'm not doing??  Opinions?

S.L.

[Mandrake]

So...now it comes down to variables such as artificial "length of day" lighting.  What works "best" for general growth, and (drum roll for my million dollar question) what lighting conditions do I need to provide to induce flowering in Lophs and other cacti???  I've owned SO MANY cacti for so many years, and not once have they produced a flower based on natural light from our window sills.   

The requirements for blooming depend on the type of plant, and of course that applies to cacti as well. You have long day plants (flowering when the hours of light exceed a certain "critical photoperiod" number), short day plants (flowering when the hours of light go below that critical photoperiod) and day neutral plants, that will flower regardless of the hours of light received.

Other factors like age, nutrients and environmental conditions are often important. I've had many cacti too, and some will flower yearly, starting in may-june -which makes them long day plants- others will flower in fall -short day plants- and others won't flower at all, simply because they are not old enough, or they are not receiving what they need. So the only way to know is to find out about the particular profile of every type of cactus. Luckily, there's plenty of members here who have experience and can give you good tips. That would make an interesting thread.

As for general growth (vegetative growth) some gardeners go as far as to leave their indoor cacti, generally trichocereus, in a constant 24-hour light period. That appears to work for some plants that are meant to stay in permanent vegetative growth, but as far as I've read and according to my experience, that is not optimal in the long run. I personally would not leave plants permanently under a light period longer than 20 hours. There's metabolic processes that generally require some time in darkness. But again, the particular requirements of every species have the last word.

Cheers,

Mandrake

[Sunshine]

Thanks for the link mandrake. I learned a lot from that +1

A friend of mine thinks that barometric pressure changes during the seasons may play a role in loph flowering. He changed light hours during winter yet still could not get them to flower. I don't remember the exact details of his experiment. But he seemed pretty adamant that barometric pressure played a role.

[Mandrake]

That's certainly possible. Barometric pressure is definitely involved in the set of environmental conditions that trigger blooming in some species, and lophs come from an area where atmospheric pressure is generally high, and probably the changes during the year are big as well. Too bad we cannot control that parameter easily in order to find out...

Thank you,

Mandrake