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Does anyone have a suggestion on grow lights up to 20" in length?  I'm new to this and am trying to set up my growing station.  :-)  Where do I obtain?  What should I be looking for?   I was looking on Amazon but don't really know what to get and if there are other better sources.

Thanks

The issue of lights for plant illumination is very complicated.  i bought these from Amazon.  I use them to augment natural light in my greenhouse.  Easy to install.

8FT LED Shop Light 10 Pack, Hanging/Surface Mount 6000K/White High Output T8 LED Ceiling Lighting, Plug & Play 72W 11520LM, Linkable for Garage
Brand: Phiwicsh

Quote from: lreed on May 14, 2025, 01:01:50 PMDoes anyone have a suggestion on grow lights up to 20" in length?  I'm new to this and am trying to set up my growing station.  :-)  Where do I obtain?  What should I be looking for?  I was looking on Amazon but don't really know what to get and if there are other better sources.

Over the past few years I have purchased an assortment of smaller grow lights, ranging from 6x12, 12x12, 12 x 24 inches/15x30,30x30,30x60cm; linear lights 12-48"/30-1.2m. Currently, they are installed in rectangular arrays on two shelves where I have been successful growing near tropical miniature aroids. All are from China via Amazon, labeled as plant lights with favorable reviews.

Before you buy lighting, buy a cheap luxmeter - you should be able to get one for $25 or so. Because we humans have irises, using eye-sight to judge anything is beyond pointless - most people can read a book at around 100 lux whereas very bright sunlight can be 200,000+ lux.

Most LED grow lights aimed at the amateur are actually a con, although extending photo-period is simple enough.

Have a search around the Philips Lighting horticultural web-pages to get an idea of what is science from a company that has been heavily involved in horticultural lighting for approaching 100 years. They cover growing room lighting - where there is no natural light at all, and also lighting to augment daylight, particularly for greenhouse crops such as tomatoes. They also cover ornamental crops too, but there are no massive differences in producing lettuces or orchids (for instance).

I have experimented in augmenting daylight, but found it impossible to achieve without resorting to very expensive professional kit simply because the shadow from the installation cut more natural light than the lamps added.

To give some idea - growing rooms require around 600W of LED lighting per square metre.

If you buy a luxmeter you will also discover that lighting has to be very close to the plants, simply because you want the light from each lamp concentrated in an area, not allow it to cover large areas.

Take a look on EBay at ad's from Chinese growers producing Sarcocaulon - some of the show the lighting set-up, although it takes some figuring out at magnification -
https://www.ebay.co.uk/itm/315765528654?_skw=sarcocaulon&itmmeta=01JV9HEYCY411KSV2V6HXARMV5&hash=item498517984e:g:4fEAAOSwfaFm6sNN&itmprp=enc%3AAQAKAAAA0FkggFvd1GGDu0w3yXCmi1eiylL%2BhCCx0qybaYHPQclvKVX19C4UegVl%2FLHNKbbjYg%2FzEOYO%2FqocyKng3FTgsXXNl2UVTrbHYqUYRB%2FKbgnGLZNjbC9rcnuQ9bQcI81tjhWLX2zISZinyFfT3Ku9nAFVHDlKqg0IK4s0P1KDEoI6qZVCpgzUBMr2KQGp5NEX7zrFtYMT6OqbFQFcLmcx3dyECk57sv7%2Ftzp579HsLigU%2BhNTdM1dJasIrZTrgo6eVv6U3aCKz1LfnISugAtFxAs%3D%7Ctkp%3ABk9SR87mu7HaZQ

Quote from: CG100 on May 15, 2025, 01:07:34 AMBefore you buy lighting, buy a cheap luxmeter - you should be able to get one for $25 or so. Because we humans have irises, using eye-sight to judge anything is beyond pointless - most people can read a book at around 100 lux whereas very bright sunlight can be 200,000+ lux.

Most LED grow lights aimed at the amateur are actually a con, although extending photo-period is simple enough.

Have a search around the Philips Lighting horticultural web-pages to get an idea of what is science from a company that has been heavily involved in horticultural lighting for approaching 100 years. They cover growing room lighting - where there is no natural light at all, and also lighting to augment daylight, particularly for greenhouse crops such as tomatoes. They also cover ornamental crops too, but there are no massive differences in producing lettuces or orchids (for instance).

I have experimented in augmenting daylight, but found it impossible to achieve without resorting to very expensive professional kit simply because the shadow from the installation cut more natural light than the lamps added.

To give some idea - growing rooms require around 600W of LED lighting per square metre.

If you buy a luxmeter you will also discover that lighting has to be very close to the plants, simply because you want the light from each lamp concentrated in an area, not allow it to cover large areas.

It is difficult and expensive to support plants that really want full sun, but it is much easier to support plants that tolerate some shade, since the illumination is much less than half...judging by my back yard, most "light shade" plants do fine with about 10-20% direct sun and no direct sun the rest of the day. My lights are about 150W per square meter, and shade plants are kept about a foot/30cm away, bright loving plants are much closer (there is a Pachypodium that is placed about 2"/5cm from the LED chips).

If we are talking South Africa, a great deal of the country gets some of the highest insolation levels on earth.
Insolation is complicated by day length as that can be quite high here in the UK during summer simply because we have long days, whereas day length varies only by around 4.5 hours in Cape Town, shortest to longest day, and as you move north in S African, the difference decreases. An avergae UK longest day is around 30% longer than it would be in S Africa.

S Africa receives 2-4 times the amount of solar radiation in any single year than does most of the UK.

150W of what? If it was simple incandescent lamps, that would be 1500 lumens, but over what area? Depending on the CCT and power of LEDs, 150W can produce in excess of ten times that number of lumens, but, again, over what area do they fall?

Colour also matter - simple growth is boosted the most by yellow-orange-red, some blue is needed to control internodal distance (legginess).

Without a luxmeter it really is totally impossible to say much at all about light levels. 
I set up some low CCT (2700K - rich in red, low in blue) LEDs around 8-10 inches above some pots and the plants were far "better" lit - much brighter. Actually, no, the lamps were in small reflector shades and measuring the light level on the plants showed that there was lesss light reaching them because the shade cast a shadow from the sun.
The plants looked "better" lit because of the high red content of the LED light - human eyes are more sensitive at the short wavelength end of the spectrum - the red end.

An extremely clean greenhouse will cut something like 30% of any external light (usually sunlight). A dirty one will cut 50% or more, but it is not possible to see that stepping into a greenhouse - it simply isn't obvious at all. I went through the exercise last year - I cleaned all the glass, inside and out and got 30% loss clean, 50% loss before I cleaned the glass, and although there was an obvious film on the glass no-one would ever guess the effect, unprompted.

Quote from: CG100 on May 15, 2025, 08:28:42 AM150W of what? If it was simple incandescent lamps, that would be 1500 lumens, but over what area? Depending on the CCT and power of LEDs, 150W can produce in excess of ten times that number of lumens, but, again, over what area do they fall?

Without a luxmeter it really is totally impossible to say much at all about light levels.

150W of consumer plant light LEDs that are reasonably well focused towards the plants without reflectors. Par meter says 300-400 at 6"/15cm, which is way less than what is recommended for sun plants, but is too much for some of the shade growing aroids (they are nearly a foot/25-30cm from the lights).

You have a PAR meter?
The only one that I could find that anyone thought was accurate was a Hortipower PG200N, something like $4000. To pay significantly less should shout that whatever it is isn't actually useful/accurate.

So-called PAR meters that you have to dial in the source - sun, LED etc.- are hopelessly inaccurate - they are just measuring lux and using a simple calculation to come up with a PAR figure, which asumes that the source you have selected has a certain spectrum.

That said, cost and (accurate) PAR are massively important commercially - people have to make a profit, unlike hobbyists.

That said again, growing room levels are aimed at around 400 - 1100 micro-mols/second/square metre, depending upon distance from the source.

20230124-gridlighting-photosynthetic-flux-density.pdf

Typically, LEDs used for supplemental lighting in commercial set-ups are very narrow strips (low shadow/shading) and also very directional.

Case browser | Philips lighting

What are you trying to achieve with extra lighting? Philips have masses upon masses of information available online.
Also useful -

Solar (Sun) Intensity By Location and Time - Engaging Data

Solar Insolation Map for the World | AltE Store

Quote from: CG100 on May 16, 2025, 12:14:05 AMYou have a PAR meter?
The only one that I could find that anyone thought was accurate was a Hortipower PG200N, something like $4000. To pay significantly less should shout that whatever it is isn't actually useful/accurate.

That said again, growing room levels are aimed at around 400 - 1100 micro-mols/second/square metre, depending upon distance from the source.

20230124-gridlighting-photosynthetic-flux-density.pdf

Typically, LEDs used for supplemental lighting in commercial set-ups are very narrow strips (low shadow/shading) and also very directional.

Case browser | Philips lighting

What are you trying to achieve with extra lighting? 

Hydrofarm Photobio. Is it accurate? Who knows, and I don't care a great deal. Mostly it is used to check relative lighting levels for plant placement or light height adjustment. I've learned what particular plants want, particularly how little light certain ones want. Could I use an app or gotten a cheaper meter, Sure, but this meter is a convenient package, within my price zone...the small cord attached sensor is nice.

Given that I have poor natural light inside, my only option is to use artificial lighting for plants that won't survive outside. The ones I grow are tolerant of cool tropical temperatures as I am unwilling to run supplemental heat, beyond the heat from the lighting fixtures. Also some seedling starts, the lighting chamber also serves as part of the warm summer storage area.

Miniature geophyte aroids. Some Typhonium, Amorphophallus ongsakulii, myosuroides, and X Majda. A. ongsakulii pays for the setup...I'm looking forward to the extent of the miniature forest this year...late, because the move has delayed planting.