Gardening Ideas forum: Dynamic lighting to achieve houseplant goals

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Name: Ian
Brooklyn, NY, 11231 (Zone 6b)
Araceae über alles!
Houseplants Container Gardener Foliage Fan Aroids Region: New York
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Hagbard
Sep 18, 2017 5:49 PM CST
There are several ways in which one can use light to manipulate their houseplants - and as a professional photographer (of architecture, and not of plants), I know an awful lot about light. So I thought I might share a few things.

One thing that ought to be taken into account is color temperature. For those unfamiliar with judging warmth versus coolness in light, take a look at the Wikipedia article on color temperature, or consult your local photographer. In general, a tungsten light bulb is about 2,700K - the K is Kelvins, a measure of CT. Daylight is typically much cooler - around 5,500K. Why is this important? CT has an effect on which parts of the visible spectrum are available for absorption by the plant. Think of the way a day passes - the blues of civil twilight, an orange sunrise, a cool, blue-skied day, an orange sunset, and back to twilight blue. The plant absorbs an awful lot over that time!

It's important to note that color temperature does not mean consistency across the spectrum. Fluorescent lighting is the worst - worse than daylight-balanced tungsten, which is second to LED lighting. But all LED lighting is not created equal - you need to understand the strength of various bulbs - that is the watts:lumens ratio, and the various sorts available.

Here is one of the grow areas I've managed to jerry rig in our little Brooklyn apartment:

Thumb of 2017-09-18/Hagbard/7c10dd

I have a pushbutton key fob that uses RF signals to turn on or off any of three light sources here - first, the little generic 2,700K 40W equivalent 400 lumen fridge-sized bulb in the lamp in the top right. This is mainly here as a night light, as my wife can't see in the dark terribly well. It's also a little additional light for small plants to phototrope upwards towards. Four feet away facing this station, I have a Husky LED contractor's worklight on a stand; it's a bright white, 4,000K, 3,500 lumen beast that hits all of these plants, as well as a second section that I can't fit into the photo, but which does not get hit by the third array - which is a powerstrip with two segregated 5,000K 100 watt equivalent 1,700 lumen Cree daylight balanced bare bulbs.

Why all this effort? I have three zones, each hit by three different varieties of lighting (not counting the nightlight). The warmer light - the 3,500 lumen Husky beast - is run from sunrise to sunset. The plants that are only seeing this light are getting the amount of light that they would naturally get at this time of the year at this latitude. This helps to reset their "biological clocks", and with auxiliary methods such as keeping it cool in winter and warm in summer - what certain spouses might refer to as "we suffer so your plants are happy" - and with careful humidity control, you can trick plants into flowering that don't normally flower indoors; into creating seeds, as I do with some of my palms, etc.

The zone that gets hit by both lighting arrays (which is pictured, with the top shelves getting maximal light and the bottom shelves still getting a lot), gets a bit of this effect from having the light *decrease* at sunset, but I leave the cool lights on until I go to bed. For fast plant growth, more light is almost always optimal, and because these don't toss out UVA or UVB like the sun, you can't scorch plants by overlighting with LEDs.

The zone that only gets the cool (5,000K) lights (behind the spread of the Husky) is ideal for plants that one wants to keep growing at the same speed year-round, in order to staunch flowering and to keep annuals living long past the grim reaper should come for them.

It's important to note that, as in most things, LED lighting should be evaluated based on the reputation of the manufacturer. There are good LED lights, and there are crap ones. You buy crap ones, and you're likely getting an incomplete spectrum. And plants like the full spectrum! So if you're planning on setting up a grow station, why not make it all in one? The total cost of lighting this setup - including extension cords and a three-button remote control to allow total control over the lighting at all times, was under $100, and it costs less for any given hour to run the entire thing on full blast than it does to run a single 40W incandescent fridge bulb. Try it out - you'll be surprised at the results!
Name: Joanna
North Central Massachusetts (N (Zone 5b)
Life & gardens: make them beautiful
Million Pollinator Garden Challenge Vermiculture
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joannakat
Sep 18, 2017 6:07 PM CST
I'm going to have to print this one and keep it handy for reference. I have one full-spectrum light bulb in a lamp that's on a timer and I thought I was being smart! The results are amazing, but I've been wanting to know for a long time how I can maximize the use of lights.

I tried a warming light, the type used in chicken breeding, to help with sprouting seeds. It was great, and then it wasn't (burned all my seedlings!)

Thanks for posting this! I can see you put a lot of thought into it. Thumbs up

Thumb of 2017-09-19/joannakat/7673db

AKA Joey.
Name: Ian
Brooklyn, NY, 11231 (Zone 6b)
Araceae über alles!
Houseplants Container Gardener Foliage Fan Aroids Region: New York
Image
Hagbard
Sep 18, 2017 6:36 PM CST
Thanks Joanna! I suppose that growing up with a father who was an engineer working on optics at the Eastman Kodak Company for over 35 years gives me a leg up on lighting-related things - I was playing with (cheap) early LEDs back in the 80s...

Anyhow, one thing I forgot to mention in the article is not to cluster bulbs - my two Cree 100W equivalents are a few feet apart, for maximum coverage. Smiling
Name: Joanna
North Central Massachusetts (N (Zone 5b)
Life & gardens: make them beautiful
Million Pollinator Garden Challenge Vermiculture
Image
joannakat
Sep 18, 2017 6:45 PM CST
Hagbard said:
Anyhow, one thing I forgot to mention in the article is not to cluster bulbs - my two Cree 100W equivalents are a few feet apart, for maximum coverage. Smiling


Does clustering them multiply the wattage?
AKA Joey.
Name: Ian
Brooklyn, NY, 11231 (Zone 6b)
Araceae über alles!
Houseplants Container Gardener Foliage Fan Aroids Region: New York
Image
Hagbard
Sep 18, 2017 7:26 PM CST
joannakat said:

Does clustering them multiply the wattage?


No, it just ensures that all the light is going to the same place. If you spread them out, you're bound to hit more parts of more plants.
Name: Joanna
North Central Massachusetts (N (Zone 5b)
Life & gardens: make them beautiful
Million Pollinator Garden Challenge Vermiculture
Image
joannakat
Sep 18, 2017 7:38 PM CST
Thank You!
AKA Joey.

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