Plant lighting for beginners

[Bonsai Nut]

I am going to start this thread with this post, add to it as I have time, and eventually compile it into an article.

There have been a lot of requests for information on artificial lighting for bonsai (particularly at this time of year). I wanted to write a reference piece that was both scientifically correct, but accessible to people who don't want to learn phytobiology

Let's start with a few basic terms. Many people think of lighting in terms of "watts" or "wattage". This is an incorrect artifact from the days when all lighting was incandescent, was more or less the same efficiency, and the more power a bulb would draw, the more light it would generate. Wattage is actually an electrical term that indicates the power draw of a light. Volts x amps = watts. You can have a bright light that burns few watts. You can have a dim light that has a high wattage. What we are interested in is LIGHT which is measured in LUMENS.

Even lumens are a little complicated, because lumens are a measurement of all light generated by a source that is visible to the human eye. But to keep things simple, think of lumens as general "brightness" of a light source. If you have a light source that generates a lot of lumens for few watts, that light is considered more "efficient" in terms of generating more light for less cost (in terms of cost of electricity used). For a historical perspective, incandescent bulbs generate about 10-15 lumens per watt. Compact fluorescent bulbs (CFL's) generate 50-60 lumens per watt. LED's generate 100 lumens per watt (or more). (These are broad generalizations using a 60 watt incandescent bulb as a reference point). Even within one type of technology there will be a range of results - with cheaper LED's yielding lower lumens per watt, and more technically advanced LED's yielding higher lumens per watt.

But wait - there's more! Lumens measure light visible to the human eye. Do plants care? Not really. The human eye has evolved to be very sensitive to daylight yellow light. Plants only care about photosynthesis. It turns out that plants have two different types of chlorophyll (creatively named "chlorophyll A" and "chlorophyll B") that absorb light and use it to generate energy for the plant through the process of photosynthesis. Each type of chlorophyll absorbs a slightly different band of light. So as plant keepers we want our light sources to specifically generate light in the bands that plants use for photosynthesis. This type of light has a fancy measurement as well - it is called PAR which stands for "Photosynthetically Available Radiation". For our artificial lighting needs we want lights that generate the most PAR for the lowest cost - anything else is extraneous. This is why professional grow lights generate light that looks strange to our human eyes - they generate light in the narrow bands of red and blue/violet radiation that plants absorb for photosynthesis. Put differently, plants in sunlight appear green to us, because that is the light that they don't absorb

Ok so next let's talk about light spectra...

 

[GrimLore]

This is why professional grow lights generate light that looks strange to our human eyes - they generate light in the narrow bands of red and blue/violet radiation that plants absorb for photosynthesis.

A quick photo representation of what it looks like in a solid white room -



Grimmy

 

[Bonsai Nut]

44% of the radiation from the sun is in the form of visible light.



Looking more closely at the spectrum of visible light, you can see how most of the light generated is in the light blue/green/yellow/orange spectra. The human eye has adapted to be most receptive to daylight lighting, so our eye can actually see orange and red lighting fairly well. Animals that have adapted to night-time lighting are more receptive to blue lighting (which is why many night time zoo displays are lit with red lighting where you can see the animals but they cannot see you).



Getting back to plants and photosynthesis, we can measure the bands of light that plants absorb for energy. Here they are:



You can see how plants use almost NO green or yellow light for photosynthesis. It is ironic that the human eye is most responsive to light spectra that plants use least... and it is one reason why normal household lighting may be uniquely ill-suited for growing plants - because many household bulbs generate a lot of yellow light.



Every light source (like the sun, or a light bulb) generates its own spectrum. Here is the spectral chart for an incandescent household 60 watt light bulb:



Woah! Not only can you see how little blue light it generates, but you can also see much of its energy is in the infra-red range (which is why incandescent bulbs "give off" so much heat). Clearly trying to use a standard incandescent bulb to grow plants would be inadequate.

 

[Bonsai Nut]

So now let's start looking at bulbs and technology. As we saw above, we are looking for the double "camel hump" of PAR lighting, in the most efficient form possible. In general, we can get there two ways... by having a broad spectrum "continuous" or "full spectrum" light source, where the plants use some of the light, but don't use the rest. Or we can have a a narrowly targeted "discontinuous" spectrum light source, where we try to generate light ONLY in the narrow bands that plants use for photosynthesis. There are pros and cons of each approach, and it is important to note that there is no perfect or best solution.

 

[Bonsai Nut]

By the way if people want to ask questions or make comments, feel free. I can edit my posts at will or move them around if necessary...

 

[ABCarve]

So now let's start looking at bulbs and technology. As we saw above, we are looking for the double "camel hump" of PAR lighting, in the most efficient form possible. In general, we can get there two ways... by having a broad spectrum "continuous" or "full spectrum" light source, where the plants use some of the light, but don't use the rest. Or we can have a a narrowly targeted "discontinuous" spectrum light source, where we try to generate light ONLY in the narrow bands that plants use for photosynthesis. There are pros and cons of each approach, and it is important to note that there is no perfect or best solution.

How about a list of different type bulbs along with their pros, cons and more appropriate uses? I know this could be a book but I'll take whatever you want to offer.

 

[Cypress187]

I'm getting my Phd here

 

[thumblessprimate1]

Great info. This would be useful if I start growing ficus one day. I think I would be interested in using an LED like this. I like to do my own cooling, wiring and soldering. What do you think?
http://www.rapidled.com/aurora-puck/

 

[GrimLore]

This would be useful if I start growing ficus one day.

- my thoughts on present LED technology

How about a list of different type bulbs along with their pros, cons and more appropriate uses? I know this could be a book but I'll take whatever you want to offer.

- It could be a separate book as this thread is but here is briefly what I know on the subject so far.

I am not playing with LED as they never seem to give you a lumen rating or useful life ratings.

For now I am sticking with Full Spectrum CFL and the Low watt Full Spectrum fluorescent. Like the fluorescent fixtures I showed the pictures of. Obvious to the camera full spectrum, each bulb is rated at 1093 lumens AND the "useful life" of the bulb is 10,000 hours(they will last 2 years burning 16 hours a day for 6 months). As bulbs age the coatings wear off so one must keep track of usage to gain any benefit, these toss white and glow greenish when expired but I toss them before that. Those are all house plants and do not require higher Lumen ratings to grow ok in the Winter. They produce no noticeable heat and use 17 watts each. Knowing all that I can stack them front to back on shelves to increase Lumens if I ever have a need to.

CFL lights work at low wattage full spectrum and are very useful in terrariums or light fixtures. The useful life and Lumen rating is almost always available as well. If I ever need a lot of Lumens as I do for the tortoise or in the future for plants I will probably use them -
http://www.fullspectrumsolutions.com/compact_fluorescent_32_ctg.htm?gclid=CNDGp6XUv8gCFUiQHwodJ_UMqw

No mystery or experimentation needed in my house, life itself has enough

Grimmy

 

[Redwood Ryan]

I used to think LED's weren't the way to go, but I've since changed that. LED's are great, IF you get the right LED. The typical Chinese made LEDs are of no use to bonsai growers. They focus more on marijuana growers and feature more red/pink light than blue, great for flowering but bad for vegetative growth.

The Grow Onyx by RapidLED is definitely the way to go. It gives off light in the blue spectrum and is great for growing bonsai. Here's the spectral output, taken from RapidLED's site:


Here's the rest of the specs if anyone is interested:
http://www.onyxgrow.com/veg.html

 

[GrimLore]

IF you get the right LED.

I realize that as well - I would toss out 450.00 USD and more on a proper one if I had some really special plants with needs. Right now and if I don't get back into it I find what I have works and works fine for me. What I mentioned of coarse can be improved by Lumens etc... but it still costs far far less.

Grimmy

 

[thumblessprimate1]

I used to think LED's weren't the way to go, but I've since changed that. LED's are great, IF you get the right LED. The typical Chinese made LEDs are of no use to bonsai growers. They focus more on marijuana growers and feature more red/pink light than blue, great for flowering but bad for vegetative growth.

The Grow Onyx by RapidLED is definitely the way to go. It gives off light in the blue spectrum and is great for growing bonsai. Here's the spectral output, taken from RapidLED's site:
View attachment 87034

Here's the rest of the specs if anyone is interested:
http://www.onyxgrow.com/veg.html

Oooh. That looks like a lot of fun to play with. *Thumbs up*!

 

[Bonsai Nut]

I used to think LED's weren't the way to go, but I've since changed that. LED's are great, IF you get the right LED.

A great light, but I want to comment on one thing. That is not an LED... it is an LED FIXTURE with a custom LED array. In this case, the entire fixture uses CREE 10W 6500K Cool White XM-L2 LED's. Many (if not in fact MOST) LED fixtures use a blend of different LED's to create a custom light profile that works best for their needs. In some cases, the different LED's will be located on separate color channels, so you can increase or decrease lighting, or even program them to change spectral intensity over the course of the day (starting out very blue to mimic "dawn", becoming yellow at "noon" and then fading into blue light again for "dusk").

Toss in WiFi controls and cell phone apps, and some of the new LED lights offer a mind-boggling level of customization.

 

[coh]

It'll be nice to have all this info in one place. Looking forward to additional posts!

I've been using metal halide, compact fluorescent, and regular fluorescent bulbs for the past few years for my tropicals during the winter. I have to keep them in an area with very little natural light, and it's been tricky to figure out the right combination of lighting, fertilizing, temperature. Haven't made the move to LED yet, still too expensive for what you get (in my opinion).

Metal Halide is tricky because the bulbs put out so much heat. It helps keep my office nice and warm, but have to be careful not to burn the plants...and they dry out very fast.

Anyway...thanks for doing this!

 

[GrimLore]

I have to keep them in an area with very little natural light, and it's been tricky to figure out the right combination of lighting, fertilizing, temperature.

Worst part of the whole circus is indeed balancing! I did some adjustments to the camera so it tones down the almost purple full spectrum a bit and look more like we see it.

First picture you will notice a few things - Northern exposure window Which provides just enough light for the taller office plants, bamboo, aloe, and spider plant. The Cacti and Succulents are under a 1093 Lumen Full Spectrum in the corner as they need light but handle cooler temperatures well. To the right is the Dog Grooming area and to the left the Tortoise table. The Cheap 42 inch ceiling fan runs 24 hours a day in reverse on low but it keeps the air in here moving great and quietly -

Opposite wall has a 8 foot wide, 8 foot tall and 2 foot deep closet area. I simply removed the Powder coat doors and stored them in the attic leaving rails in place. Similar storage units on each end. Over 5k Lumens of Full spectrum. The terrarium has 3k Lumen CFL -

The Tortoise table has a light array all CFL on separate timers. One is Full Spectrum Daylight, another is Full spectrum Daylight heat, and the third is a night(black) CFL that tosses a ton of heat -

A humidifier that keeps the room at between 55 and 60 percent and feeds humidity to the cold air return keeping the rest of the place non-static when the heat is running -


They all do well and although it is a white cube it works - Going to add 10k of lighting and shelves during the Summer when it is empty and it won't look so stark. for now there is over 50 plants but they are happy...

Grimmy

 

[Mike MoMo]

I finally got my grow light set up together. One day down figuring that it will take a week to see any positive or negative effects. I am running two 24" lights of america grow lights 16 hours a day. Yeah they are cheap lights but I'm Bonsai Balling on a Budget. Will post pics tomorrow.

 

[GrimLore]

Yeah they are cheap lights but I'm Bonsai Balling on a Budget.

They are not cheap - just inexpensive. All of the lights you see in my pictures are that same light. They toss a little over 1K Lumen of Full Spectrum light and we have been using them for years. They produce so little heat the plants can and do grow right into them if you allow it. I am adding shelves to the blank walls and adding ten more this Summer when the plants and Tortoise are outside so I can move his table for access...

Grimmy

 

[Mike MoMo]

Thanks Grimmy! I'm thinking of getting more for the lower shelf and get my vegetable seeds started next month to better use the short Michigan growing season.

 

[GrimLore]

I'm thinking of getting more for the lower shelf and get my vegetable seeds started next month to better use the short Michigan growing season.

Good idea - make use of all the space and the wattage use on them is really inexpensive. I don't like going to WalMart but when I do I pick them up a couple there for 10.97 each - stockpiling them as I expand.

Grimmy

 

[MattE]

Thanks for all the info guys this is very helpful for me as a new person to the group.

Grimmy great set up and love the tortoise