Cactus under lights!?

[BBGONE]

What colour temperature is best for vegetative growth (of any plant, not just cacti)?

Edit: Also, is there an approximate conversion of the output of the light (in lumens) to the amount of surface area it can cover effectively?

 

Maybe those articles could be helpfull for selecting the lights

http://www.greenmanspage.com/guides/lightguide.html

Some info from another website (search engine finds a lot of them)

# Metal Halide Lamps Metal Halide (MH) bulbs emit a light spectrum which appears blue-white to the human eye. This color spectrum is more conducive for vegetative growth, or starting seeds and cuttings. High Pressure Sodium Lamps High Pressure Sodium (HPS) bulbs emit a spectrum which is more concentrated in red/orange light. This color is ideal for the fruiting and flowering stage of a plant's development. It is a good multi-purpose light as well. Conversion Lamps There are two(2) types of conversion lamps: HPS Lamps which run on MH ballasts.

# MH Lamps which run on HPS ballasts.

This type of lamp allows you to tailor the light source to the growth stage of the plant (again, using metal halide light for growth and high pressure sodium light for flowering/budding) merely by changing lamps. Flourescent Lamps Traditional T12 and T8 fluorescent lighting is simply not powerful enough to light an area more than 8-10 inches below the bulb. With the recent introduction of the highly efficient T5 technology, T5 linear fluorescent fixtures can now put out a respectable 92.6 lumens per watt. T12 lamps typically put out about 30 lumens per watt. Our T5 fluorescent lamps are excellent for starting seeds and cuttings, but are also able to produce enough light for full term growth. Because of their minimal heat output, they can be placed very close to the plant canopy to maximize the light output. Note: Halide and High Pressure Sodium are referred to as "High Intensity Discharge" (HID) Lamps.

[Gunter]

instead of reading old literature about colors to the visible eye, i'd check your specific lamps spectra against a PAR chart

HPS and MH lights come in a ton of color variations... btw, the newer CMH, made for HPS ballasts are perhaps the best lights around in terms of spectra

http://en.wikipedia.org/wiki/Photosynthetically_active_radiation

the myth of what color favors what type of growth is age old, but not actually true

http://en.wikipedia.org/wiki/Chlorophyll

Edited April 13, 2011 by Archaea

[BBGONE]

the myth of what color favors what type of growth is age old, but not actually true

http://en.wikipedia.org/wiki/Chlorophyll

 

Archaea, i'm fully aware that this is a myth, especially that green color is not utilized by plants.

I'v read a lot of articles in which was shown that under green lights the plant was grown very well.

The best light for plants is that is close to sunlight spectrum, which contains 27% of blue light (by its total energy).

HPS lights, the best i saw,- Sylvania GroLux, contains only 30% more blue spectrum than ordinary HPS lamps.

Edited April 14, 2011 by BBGONE

[Gunter]

I am not sure that the best light for plants is solar spectra,

as for green, some lights that look green to us are blue and yellow spectra rich, those would look green to the eye but contain spectra ideal for plant growth, however pure green spectra lights should give a different response, one cannot use the eye to judge spectra.

The suns spectra shifts during the day, season and depending on latitude. CRI and degrees K are ok as baseline ways to relate to solar spectra, but are not perfect.

I want to see side by side comparisons of MH and HPS 400W lights on cactus seeds and seedlings of identical source and see after a year what the difference is.

[BBGONE]

I want to see side by side comparisons of MH and HPS 400W lights on cactus seeds and seedlings of identical source and see after a year what the difference is.

 

I saw one, but i dont remember the source,

HPS and Fluorescent (cool white 6500K) lights were compared with cactus seeds germination.

Under Fluorescent lights there was muuuch better germination rate.

I also would like to see full study, maybe i will find something, but until now i have only what was written in many articles.

Spectrum and uses of HPS and MH lamps:

HPS

http://en.wikipedia.org/wiki/Sodium_vapor_light

MH

http://en.wikipedia.org/wiki/Metal_halide_light

This exerpt from the first article

High pressure sodium lights yield yellow lighting (2200 K) and have a very poor color rendering index of 22. They are used for the second (or reproductive) phase of the growth. If high pressure sodium lights are used for the vegetative phase, plants will usually grow slightly more quickly. The major drawback to growing under high pressure sodium alone is that the plants tend to be taller and leggier with a longer internodal length than plants grown under metal halide bulbs. High pressure sodium lights enhance the fruiting and flowering process in plants. Plants use the orange/red spectrum HPS in their reproductive processes, which produces larger harvests of higher quality herbs, vegetables, fruits or flowers. Sometimes the plants grown under these lights do not appear healthy due to the poor color rendering of high pressure sodium, which makes the plants look pale, washed out or nitrogen starved. High pressure sodium lighting have a long usable bulb life and six times more light output per watt of energy consumed than a standard incandescent grow light. Due to their high efficiency and the fact that plants grown in greenhouses get all the blue light they need naturally, these lights are the preferred supplemental greenhouse lights. But, in the higher latitudes, there are periods of the year where sunlight is scarce, and additional sources of light are indicated for proper growth. HPS lights may cause distinctive infrared and optical signatures, which can attract insects or other species of pests; these may in turn threaten the plants being grown. High pressure sodium lights emit a lot of heat which can cause leggier growth, although this can be controlled by using special air cooled bulb reflector/enclosures.

What was written about LED grow lights in the article http://www.littlegreenhouse.com/guide3.shtml

There is also charts and comparisons.

Just interesting about LEDs-

LED grow lights are the newest lighting option for plants. They are advertised to be the most efficient and coolest running grow lights available. We have tested several different types of LED grow lights and have found none that outperform much cheaper fluorescent grow lights of similar wattage. LED plant grow lights are also not recommended for use with plants that you want to be viewed, because they give plants an unnatural appearance when the light is on.

the reference on the study of fluorecent lights

http://www.planetnatural.com/site/xdpy/kb/fluorescent-lights.html

In summary, fluorescent lights are efficient sources of light for growing plants in specific locations or situations. Blue-red fluorescent tubes may elicit an adequate response from some crops, but cool white light is as, or more efficient for most crops. For several crops requiring especially high light intensities, the high energy discharge multi-vapor lamps should be investigated as well as high output and very high output fluorescent tubes.

At the end more scientific article on different lights for growing plants (very useful)

http://www.controlledenvironments.org/Light1994Conf/1_3_Tikhomirov/Tikhomirov%20text.htm

1) The time for maximum affectivity of photosynthesis of plant canopies appears earlier with red (600-700 nm) and later may shift to shorter wave length regions of PAR. This shift depends on specific plant reaction to spectrum of PAR;

2) The relative effectiveness of blue rays increases and green and red rays decreases with higher levels of irradiation (Fig. 2 and 3);

3) Maximum photosynthesis of canopies is possible only under combinations of blue, green and red radiation. Any kind of combinations of two of these wavebands or with only one spectral region, always reduces productivity.

More articles (NASA research)

http://www.controlledenvironments.org/Light1994Conf/Contents.htm

Edited April 13, 2011 by BBGONE

[C_T]

germination doesn't need anywhere near the light of an adult cactus. Especially trich!

[BBGONE]

germination doesn't need anywhere near the light of an adult cactus. Especially trich!

 

This could be due too high light intensity, that caused overheating, and not due to light spectrum.

But that was just a fact of life.

Edited April 14, 2011 by BBGONE

[BBGONE]

More deep info on cacti under lights: http://cactiguide.com/article/?article=article17.php

The Light Spectrum

As for picking the "right" wavelength of light to grow plants "best", that's a bit like trying to pick the right vitamin for people to live off. You can't do it, they're all important for different things. Specific wavelengths, or more importantly specific pigments activated by light at particular wavelengths, have been shown to control the orientation of plant's leaves and flowers relative to the sun, the orientation of chloroplasts within leaves, the quantity of chlorophyll generated within leaves, the size of the leaves, the opening and closing of stomata, the opening and closing of flowers, and the induction of flowering and fruiting. Mostly these wavelengths are towards the blue and green end of the spectrum, at the red end it is mostly just chlorophyll making sugar.

Plant light sellers make a big deal out of the chlorophyll absorption spectrum and how green light is useless. There are many pigments in plants, not just chlorophyll, and plants can make use of light of any colour. Deep red light is the most efficient in terms of simple photosynthesis, but not to the huge extent usually claimed, and plants grown only in red light get leggy and overly lush. The first step is to add a little blue light, then the plants do better. Some people would claim that plants cannot be healthy without light that closely mimics full spectrum sunlight, others that monochromatic red light blows everything else out of the water. I don't see huge differences between them and going to extremes in either direction has big drawbacks.

UV "stresses" plants and not much else. There is certainly no biological need for it and plants can grow without it. In the case of cacti, stressing the plant can be desirable, it produces heavy and dense spination, skin colouration, and "stunts" plants so that they are flatter. Shorter light wavelengths in general produce plants with shorter internodes, smaller leaves, and more branching. Its not quite that simple though, because the primary controller of internode length is the relative levels of red and far red (and near infra-red) light. This is one of the reasons that incandescent lights and HPS lights can produce severe etiolation. This particular combination of light wavelengths is generally ignored in the whole blue/red debate, partly because it is difficult to see the relevant wavelengths and partly because it is even more difficult to control them.

Anecdotally, some cacti will not flower without high levels of UV. The high altitude Andean dwarf Opuntioids are one group, but potentially other mountain species like Pediocactus won't do well without UV. This is particularly relevant for plants which spend pretty much their entire lives behind a piece of glass or plastic which blocks virtually all the UV. It is obviously difficult to separate the effects of UV from full sun at high altitude from just having extremely high light intensity. As you'll see from reading the lizard pages, its hard to get anything like outdoor UV levels from a light. I don't worry too much since my plants get sun in the summer.

-HID (High-Intensity Discharge) Lighting

HID lamps are just not worth messing with at low powers, inefficient, poor life, hot, and generally not worth the trouble. Normally I would suggest you only use HID lights from about 250W upwards, ideally 400W, for their high efficiency and ability to provide high light intensity over a good sized area. Smaller lights produce less light, lose output fast, have shorter lives, and don't cover a large enough area. They could be used for high intensity lighting on a small number of plants, for example 150W would be good up to perhaps five square feet. That said, I would normally recommend something like a 4 x 54W T5 fluorescent system for someone looking at 150W HID bulbs.

-Metal Halide Lighting

Metal halides have long been the standard choice for growing high light plants, but that choice should no longer be automatic. High performance fluorescents such as T5HO and the newest VHO tubes offer competitive performance and some advantages. Few people will offer an unbiased comparison because they are trying to sell one product or the other. Metal halides offer a small extremely intense light source with high efficiency, but lumen maintenance, lifetime, and cost cannot compete with the best fluorescents. A good 125W pulse start metal halide will offer similar efficiencies to high intensity fluorescent lighting in a much smaller package, but will lose 30% of output in the first 5,000 hours, so there would have to be a pressing need for small size or extreme light intensity to make this worthwhile. Mostly you should stick to the efficient and widely available 400W metal halides which are more convenient than fluorescents for lighting large areas and for providing high light intensities.

Watch out for those metal halide bulbs, they will be putting out a lot less light after you've used them for six months. Historically, plant growers have replaced metal halide bulbs every 6-12 months, although they will run for several years. For a variety of reasons, plant light sellers are often still wedded to an obsolete technology known as probe-start. Modern halide lighting is pulse start, they last longer, they don't lose light as they age, they start quicker, and they are less likely to explode, but they need a different ballast. Pulse start ballasts and bulbs are generally more expensive, but plant lighting is often sold at a huge markup anyway and you should be able to find a pulse start ballast and bulb for less than $170. You'll mostly find them sold as business and warehouse lighting. Another worthwhile efficiency improvement is to get an electronic ballast (often called a digital ballast by plant light sellers although strictly that isn't quite the same thing), they will save about 10% on your electricity bill.

Another very confusing issued much abused by those trying to sell you something is heat. You will get the same amount of heat from 400W of fluorescent tubes as you do from a 400W metal halide. You might get it in different places, but don't be fooled by the fact that one is a tiny raging hot bulb and the other is many metres of moderately warm glass. Still, metal halides inside a home have several disadvantages including fire hazard and fading nearby fabrics. And of course if you don't need 400W of light then there's no point wasting all that electricity and getting way more heat than necessary. Metal halide lamps radiate more heat as infra-red (and UV also) than fluorescents which can be good on an adult cactus but may be too harsh for seedlings.

-HPS (High Pressure Sodium) Lighting

HPS lamps alone would not be a good choice for growing most succulents. They'd tend to etiolate and not grow dense spines or develop good colour. Use metal halides or a mix unless you are just supplementing natural light.

HPS is waaaayyyy better in efficiency than flourescents or metal halide in terms of lumen output but it is in a restricted spectrum that isn't always suitable on its own, certainly not for most cacti although I'd bet that Pereskiopsis would just love it. Metal halide retailers like to compare their products in PAR watts where they can exceed HPS lamps, although this is slightly misleading. When properly measured as a photon flux the HPS are still better.

HPS technology has not advanced as much as metal halide in recent years and the gap is narrower than it once was. Digital ballasts are available, but the basic lamp technology has not really moved on. HPS bulbs have always offered better lifetimes and better lumen maintenance than metal halide but they haven't improved as much so the difference is now much less. HPS lamps don't quite reach peak performance until the 600W-1000W range although 400W bulbs are pretty good. There are an increasing number of crossover HOD lights offering spectrums that are a combination of HPS and MH, or with swappable HPS and MH bulbs in the same fitting, but you always pay a price for the flexibility.

-LED (Light Emitting Diode) Lighting

Many many experiments have been documented using LED grow lights. Performance in terms of plant mass and size is comparable to other light sources at the same light intensity, although it can be very difficult to determine the true intensity of a non-white light source. The typical "red plus a little blue" LED light usually produces different growth patterns, primarily less compact and less branched plants. Note that this is in stark contrast to the claims made by LED plant light sellers who would have you believe that three LEDs running off an AA battery are equivalent to a 1000W metal halide lamp.

I look at LEDs every year or two, but so far I haven't tried them on plants. Until recently they simply haven't been powerful enough or efficient enough at producing light (compared to the best conventional solutions) to make them more than a toy. Now they are available at performance levels which are potentially useful but initial costs are still high, extremely high for commercial LED plant lights. I should probably try a small DIY LED setup but its not going to happen this winter. By next year of course they'll be another 50% better!

The specific wavelengths of LEDs are often given as an huge advantage and used to justify how a massively under-powered light can perform like its bigger brothers. This is 90% marketing hype; LEDs happen to provide light at just a single wavelength so make it into a selling point. In practice, fluorescent tubes have been available for decades providing virtually the same spectrum. The earliest were called Gro-Lux and they were not massively better than simple white light sources, and with significant drawbacks in terms of efficiency and operating life. Today you can still find similar lights being sold, google for "PURple". Gro-Lux fluorescents are still available but they now have a wider spread of light, still mainly blue and red but with other wavelengths also. Experiments have shown variable results from just using monochromatic blue and red light vs white light, sometimes a bit better, sometimes a bit worse, but don't expect the spectrum to change the laws of physics for you. The monochromatic light output, and particularly in far red and blue wavelengths, are very difficult to compare with white light sources. They will look relatively dim because our eyes don't see those wavelengths, and for the same reason the output in lumens is not directly comparable (although it can be converted if you know the wavelength), but few manufacturers will quote accurate photon outputs for their lights. They often won't give you the total light output in any units. Buyer beware!

LEDs produce such strongly directional light, without any need for additional reflectors, that penetration is actually quite good. You would have to check your particular LEDs since some produce a much wider spread of light than others. Many LEDs produce almost their their light within a 10 degree cone, much better than you will achieve with even a very good conventional reflector. An LED with a 45 degree light cone would not be so good and you would have to put it quite close or use additional reflectors. The large arrays that must be used with LEDs naturally produce quite good directional light with good penetration. Even if the LEDs at the edge of the array are sending a little light away from the plants, the vast majority in the middle of the arrays are hitting plants even with their off-centre light. This feature is often used to provide misleading comparisons, where a very powerful conventional light produces similar growth to a small LED light simply because 90% of the conventional light never hits the plants.

There are some other interesting points about LEDs. The long lifetime is often quoted as an advantage. Typically a life of 50,000 - 100,000 hours will be quoted although some of the newer high power LEDs have shorter lives. What isn't highlighted is that the light output of an LED decreases more or less steadily from day one until it is too dim to see. You need to look carefully and see what the actual lumen depreciation is because it may become unusable as a plant light after 10,000 - 20,000 hours. Of course that is still several years and by then LEDs will cost less than a dollar and be brighter than the sun. The best fluorescent tubes lose 5% of output over a 20,000-30,000 hour lifetime, modern HID lamps 10%-20%. LEDs don't really outperform in this respect.

High power LED arrays must be very carefully designed. Cool operation is often given as an advantage, but LEDs actually produce a similar quantity of heat to other plant lights. The difference is where that heat goes. In a metal halide lamp a very high proportion is radiated away, which can be bad for plants that get too close but at least stops the bulb melting! LEDs radiate away relatively little heat, they just dump it into the semiconductor and will rapidly deteriorate without careful heatsink design. Its hard to tell by looking, but cheap LED lights will likely fail long before that 50,000 hours.

I haven't yet seen LEDs for sale which have the same lumen (or photon) output per watt as modern metal halides or fluorescents. Maybe they exist or maybe not, the only ones I've seen are in laboratories or for special order at a special price. Again, the people selling the LEDs like to claim they are more efficient than other light sources, but they also like to use what is essentially obsolete technology for their comparisons. They also like to run "tests" with poor quality conventional lighting where the majority of the light never even lands on the plants. Under those conditions, LEDs blow away conventional lighting at the same power levels, but they don't when you compare best practice setups for both types of light.

The top end LEDs available in the UK far exceed incandescents (although they still can't match the total output from a small area like a normal light bulb), are slightly better than compact fluorescents, are approaching mainstream triphosphor T8s on electronic ballasts, are still some way short of the best T5 and T8 tubes and similar up-to-date (pulse start, ceramic, digital ballast, etc.) metal halide lighting, and way short of HPS lights (which have their own drawbacks). I see reliable data from white light LEDs at around 70 lumens/W, with monochromatic LEDs a little better although you can't measure them in lumens/W. I expect around 90-100 lumens/W from my plant lights and I expect LEDs will reach that level very soon (written in 2009).

Edited April 30, 2011 by BBGONE

[Gunter]

h++p://www.growlightexpress.com/pages/ceramic-metal-halide-pv-c0-2.html

CMH are very sun like in spectra and are made for coil ballasts for HPS

these are said to be very choice lights, but i have not had a chance to try them

[BBGONE]

h++p://www.growlightexpress.com/pages/ceramic-metal-halide-pv-c0-2.html

CMH are very sun like in spectra and are made for coil ballasts for HPS

these are said to be very choice lights, but i have not had a chance to try them

 

One more choice Very High Output (VHO) fluorecent tubes (Spectralux)

http://www.sunlightsupply.com/p-12128-spectralux-t5-vho-fluorescent-grow-lamps.aspx

These T5 VHO (Very High Output) lamps are a brand new technology. T5 HO (High Output) lamps have an initial rating of 5,000 lumens. The new VHO lamps are 7,200 lumens. They have to be paired with a VHO fixture such as the Solar Wind or Solar Flare.

and Solar Flare T5 (VHO) Fluorescent Fixtures http://www.sunlightsupply.com/p-13024-solar-flare-t5-vho-fluorescent-fixtures.aspx

* 95% reflective European aluminum reflectors.

* Major brand solid state electronic ballasts.

* Dedicated 120v or 240v input power

* Heavy duty white steel housing.

* Louvered and slotted for efficient cooling capability.

* Comes complete with 2 chrome wire hangers for mounting/hanging.

* Grounded power cord.

* VHO Lamps offer 7200 lumens - 95 watts each.

* Daisy chain feature allows multiple fixtures to be plugged together.

* Do not use HO lamps with VHO fixtures.

Edited April 30, 2011 by BBGONE

[neomad]

After searching far and wide through the interwebz a few weeks ago I finally decided to buy what are known as tneon lights with a reflector for my smaller cacti. It seems that a lot of sources recommend t5 lights. For some reason t5 fixtures are really expensive here and I had a look at what a few grow shops have on offer. The tneon set was really cheap and allegedly the lights are comparable with t5s. I have one 6500k and one 9000k bulb. Here is the rather makeshift setup next to my desk:

This unfortunate fellow was gifted to me with some other cacti. He was full of rot and I cut off the roots and tip and a chunk on his side. I tried to root him before the end of summer but he only put out a couple of tiny ones. When I got these lights a few weeks ago I decided he was candidate number one. Just today I noticed that he is much fatter, looks a healthy colour and he has roots popping out of the bottom of his pot! His larger brothers also seem to be doing fine. I am quite impressed. I'll be interested to see how they are doing by the time spring gets here.

[DarkSpark]

i don't see trich doing very good under lights... the cost/benefit ratio would be quite negative.

 

i would agree, also i kind of think plants need their rest periods from vigorous growth.

I've read that HPS is better for inducing flowering and MH better for vegetative growth. Is that correct?

 

this is kind of correct with mary jane i am not 100% sure for cacti and others i cant see why not though. The HPS isn't so much better for inducing flowering but offers the plant more usable light during the flower period, or so i think anyway. the MH is a more blue light while hps is more orangey red.

So, if one was to use HPS lights to overwinter plants and keep them growing, how much surface area does one 400w light cover?

 

1M of surface area with a good shade without losing too much of the light, for the cacti you could have it higher and do a larger area though. Someone said above cacti take their light from the sides, to help with this wrap the growing area in mylar or panda wrap to maximise reflectivity of the sides !

Edited January 4, 2012 by DarkSpark

[theuserformallyknownasd00d]

Hey guys, to save another thread I shall ask here...

How detrimental to cacti seedlings would it be to keep veging them over winter in a greenhouse under lights? The seedlings will age from 2-5mths old. I dont want to ruin any chances they'll have for a healthy life, but have the space to keep them growing optimally over winter.

Dood