Research: Will Natural Light Do the Job?

digitS'

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Of course.

I was reading in a fairly recent fact sheet from Purdue (click) that only 10% to 20% of the commercial greenhouses in the northern US have supplemental lighting. Don't have a greenhouse? What about a house window? The answer would have to be, "Perhaps."

The Purdue pdf file has little information on veggies but one can imagine that they would fall in with the Marigolds and such bedding plants (they do say something about Capsicum peppers) rather than ferns or even Impatiens. The light requirements for proper growth are high.

Purdue is talking about whether a greenhouse should install "supplemental" lighting. Several decades ago, I worked at a commercial greenhouse which added supplemental lighting while I was there. The primary crop was cut flowers and the flower holidays, if you think about them, are nearly all during the months when there is limited sunlight. The extra light made quite a difference for Christmas and Valentine production, as you might imagine.

Okay, back to that south window . . . You can look at the maps for the natural light during various months. This is March . . . ;). Here are some maps that make it a little easier to see what is going on now and what has been going on during the time gardeners are sowing seed for plant starts:

http://www.gpnmag.com/sites/default/files/supplementallighting.pdf

As you can see, the author is essentially saying that throughout nearly all of the US during March, natural light should provide everything that is necessary for proper growth. Unfortunately, I live in 1 of those 2 red blotches :/ where supplemental lighting would provide a (not small, but) moderate help.

Cloudy weather at this time of year is a source of annual frustration . . . I will be dragging an 8' light fixture into the greenhouse if what is going on currently continues much longer. But, until the plants are actually in the greenhouse :rolleyes:, seedlings are showing up in a south window here indoors. Fortunately, it is large. The tree nearby is a deciduous and will not leaf-out until late April. There is also NO roof eave close to this window.

Do you need to grow under a light? Probably not if you live where you are "in the clear" on those maps! And, if you have a window like mine. BTW, I've taken the screen off of it and cleaned the glass, inside and out, a few days ago :cool:.

Don't push the plants with too much heat. That may be difficult in a south window but if you can isolate the room from room temperature in the rest of the house, that may help. Those commercial greenhouses are generally growing plants in temperatures as much as 10 cooler than the 70F most of us like to keep our homes.

Steve
 

Greenthumb18

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Great research Steve!
I always use my windowsill to keep my seedlings on there for light. I don't use supplemental lighting and they do fine. Plus it saves money from having to use lights. I do build a greenhouse and still use the sun as the natural light source. Maybe theirs something about natural sunlight that supplemental lighting can't be compared to.
 

The Mama Chicken

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I don't have a single south facing window in my whole house, it's really weird. All of the other windows that might work are either shaded by the giant live oak tree next to the house (it's actually much bigger than the house) or in the kids rooms. I will just stick with my lights until I get the greenhouse built.
 

catjac1975

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A west facing window provides excellent light for growing. I have a south facing greenhouse that I used with out supplemental light. I have added a 3 tiered light stand and the plants grow bigger and straighter. The natural light plants were just as good just tend to lean towards the window and took a bit longer to grow. The best influence in seed starting has been bottom heat.
 

digitS'

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Mike, it may be that lots of people sink a lot of money into grow lights when it might not be at all important for them to do so. We have plenty of gardeners starting plants in their basements and other dark corners and they don't have a choice but most homes (other that The Mama Chicken's ;)) have south windows. Sometimes, they are well-suited for plants.

No doubt, it is fun and useful to have the light set-ups. In the hands of a knowledgeable indoor gardener, their worth can be proven season after season. Greenhouses are great if you can be attentive to that changeable spring sunlight & weather conditions. Or, have a much more automated system than I've got :rolleyes:.

Many folks are really going into gardening because they are trying to save money on food costs. So, the first thing they do is spend a hundred bucks on hardware?!? It may make a lot more sense for beginning gardeners to sink $100 into hand tools and fertilizer. Then, they can scrunch up at their computer desk a little closer so as to allow the seedlings to get the best light -- I have :p.

Steve
 

NwMtGardener

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Thanks for the link to that article Steve! Of course i'm in a red splotch zone... :/ never considered keeping my plants COOLER than the rest of the house either!
 

digitS'

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Heather, the commercial outfits do these trade-offs between energy costs, time and quality. They also use things called "growth regulators" to control stretching. Yeah, they spray the plants with chemicals and not just to kill diseases & bugs :rolleyes:. One of the growth regulators is called "Downsize." Do most gardeners think about "downsizing" their plants??

Okay, to try to control stretching during low-light growing conditions - the University of Delaware (click) recommends allowing the early morning temperatures to drop all the way to 50 to 55F for vegetable starts. I suspect that not too many Americans are willing to have their homes go below 55, overnight! Still, their daytime recommendation of 60 to 70, might be a little easier to hit.

Gee, our barometric pressure is below 27" this morning! Evidently, the air pressure isn't from a nice, sunny high pressure area . . . must be from the 50mph wind gusts
shocked.gif
!! So . . . how might barometric pressure effect plant growth?

Steve

where rain will turn into snow, soon . . .
 

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