Grow Light Question

I've read that seedlings need 20 hours or so per day under a grow light. When it's warm enough that I can set plants outside for 8 hours of natural sunlight, do the seedlings really need to go back under the lights for 12 more hours after that?

Once I can get them outside that is all they get.

Landarch, it'd be NICE if they got that much... But keep in mind we're dealing with plants - something that's been around a lot longer than us! They know what to do...

My seeds are set in an east-facing window. What light they get is what they get. I don't have room to put grow lights in there. And they're doing fine.

So if you are using grow lights, how many hours would you use them a day? 12, 16, 20?

Say, spring in Texas gets 12 hours/day and summer gets 16 hours/day which would be recommended?

Right now I have mine going 20 hours/day, just two CFLs about a foot above seedlings.

RY

My thinking is the time is irrelevant, plants use the length of the day to determine the seasons.
The thing we are interested in is the lumens produced by the bulbs. Since most don't understand lumens we can try and use the watts consumed by the bulbs. One of my CFL fixtures has two 85 watt bulbs. I use it for a couple of weeks than a re pot for the leggy tomatoes and outside during the day. Hope this helps.

When mine are under lights, they are on all the time. Once out, no more light other than sun.

Scorpio Rising wrote:When mine are under lights, they are on all the time.  Once out, no more light other than sun.  

I think that is a good strategy. I'm probably going to start going 24hrs with lights.

I did read somewhere that plants need a period of darkness.  Can't remember where, though.

Same as we humans needs darkness to sleep?

Maybe it was with the instructions with my AeroGarden?

But then, worms don't sleep, they are on the go all the time, slaving away for us in their worm bins and underground.

Useful information http://www.ext.colostate.edu/mg/Gardennotes/142.html

With just 4 foot flourescent shop lights on, at about 2 or 3 inches above the seedlings, mine stay on for 15 hours then shut off. The closer they get to hardening off outside, the time under lights will decrease to more closely match daylight hours outside.  If the light source is too far away, that's when plants get "leggy."

Boz wrote:Useful information http://www.ext.colostate.edu/mg/Gardennotes/142.html

And one sentence from that website tells it all ...


"When starting transplants indoors, give plants 12 to 14 hours of light per day. Plants are generally intolerant of continuous light for 24 hours."

Interesting. I agree, from the full spectrum sunlight, a plant needs a break (don't we all?). Undecided about my set-up, which is (2) 4ft. Flourescent doubles. Generally about 2 inches above plants. It is not sunlight quality by any means!

I don't have enough light to grow most vegetable. My plants are currently under a two foot four bulb florescent fixture. That is not enough light but hopefully  I can start putting them outside by the first of April and they will be alright. The Toms are the most demanding and we can always plant them deep. The lights are on for 12 hours.

Personally, if you are just getting them started, I would go all in. 24/7

http://forums.gardenweb.com/discussions/2006260/what-are-the-consequences-of-leaving-lights-on-24-7

Most research is done on yields of plants raised cradle to grave under lights. I don't have the right lights for that, nor the inclination to do so. I am raising starts in a warm and light environment. And then obviously moving to my SFG.

It is all an experiment! Tell us what happens for you!

This year the days have been relatively warm and sunny so all my plants are getting full day sun (after hardening off for 2-3 days in dappled shade).  Nights have been mild enough to leave out all night...I do bring in peppers and eggplants if it gets to chilly.

I posted the original question because I've been reading different things about grow lights...some think 24 hours a day is ok...some talk about the plant's Krebs Cycle and how plants need 4 hours of darkness per day.  

I've tried so many different ways and truthfully can't tell the difference once the garden is in full swing.  Last year I was really tired of plants getting full sun all day, then carrying everything to the basement for additional light to get to 20 hours...all to be carried outside again the next morning.  One rule I created for myself is that when any part of gardening becomes a burden I shut it down...it should be fun at every step.  

Before asking the original question I was hoping to find a really easy answer while surfing the net...something like 1 hour of real sunlight is equal to 4 hours under a specific grow light...didn't really find anything out there that simple.

landarch wrote:
Before asking the original question I was hoping to find a really easy answer while surfing the net...something like 1 hour of real sunlight is equal to 4 hours under a specific grow light...didn't really find anything out there that simple.

That is exactly what I have been asking myself as I read this thread.  Also, is filtered sunlight (cloudy conditions) better for the plant growth or would it be better to bring the plant indoors and put under T-8 lights on cloudy days.

The Colorado Univ link above indicates heavy clouds or bright bright plant lights are about the same, 500-1000 lux or foot-candles. A cloudy day may be a good way to introduce the leaves to their future bright light. ??

landarch wrote:This year the days have been relatively warm and sunny so all my plants are getting full day sun (after hardening off for 2-3 days in dappled shade).  Nights have been mild enough to leave out all night...I do bring in peppers and eggplants if it gets to chilly.

I posted the original question because I've been reading different things about grow lights...some think 24 hours a day is ok...some talk about the plant's Krebs Cycle and how plants need 4 hours of darkness per day.  

I've tried so many different ways and truthfully can't tell the difference once the garden is in full swing.  Last year I was really tired of plants getting full sun all day, then carrying everything to the basement for additional light to get to 20 hours...all to be carried outside again the next morning.  One rule I created for myself is that when any part of gardening becomes a burden I shut it down...it should be fun at every step.  

Before asking the original question I was hoping to find a really easy answer while surfing the net...something like 1 hour of real sunlight is equal to 4 hours under a specific grow light...didn't really find anything out there that simple.

  Some times we get tied in knots  about this natural cycle of day light and artificial light thing .

 Plants need ultraviolet light and infra red light waves to produce chlorophyll plus other light waves found in the natural light spectrum .
 As well as varying levels of infra red  penetrating the soil they  help germinate the the seeds  ( think this is as much to do with heating effect as it is to do with weak infra red penetration stimulating the seed germ. 

  CFL. & standard tube lights have a fairly low levels of UV & infrared light as well as producing a bit of heat .

 There are specialist  GROW LUX tubes for vivariums , fish tanks and also for horticultural use that emit  greater levels of IR & UV ...... developed specifically for growing plants along with some sodium & some mercury vapor lights

 The later two  having to be a considerable distance above the crops to stop the large amounts of generated radiated heat  destroying the plants.

The GROW LUX tubes are usually suggested to be set about a foot above the crop & not be left on 24/7.
I think this is to give a longer level of guaranteed  working light as much as anything else .. It allows the makers to say 1,000 hours use when used 12 hrs a day rather than  500 hrs  if kept on 24/7

 Lots of seeds germinate and grow into fairly health plants under these lights. providing the moisture level & temperature is reasonably correct .  How ever don't be led to think you can grow the pants from seed to the plate under these lights , at some stage you must get them out into sunshine .

 Now we have LED lights that are almost cold wrt heat but designed for optimum levels of growth coming into the market place there is still the need for a bit of heat in the soil as well

 Standard 50 watt incandescent light bulbs under a shelf of seed trays  is often enough to give this heat as are some of the older type rope lights  when set inside a shallow frame . putting a variable thermostat ( $ 10 USA) into the power line can see you with a very cheap effective heated bed that can be set to the optimum soil temps for germination .

 Years ago before rope lights arrived on th every day scene I wired three 10 watt screw in pygmy bulbs in holders in parallel and screwed them on to a length of wood inside a 20 x 24 x 12 deep plastic packing crate .
At each corner of the crate I put a half brick and over these half bricks  put the cooling grid off a tall fridg, e cut down to fit box  ( acts as an even heat dissipater ) .  On top of the grid I could sit three seed trays at a time. I then  covered the top of the box in a thin sheet of perspex .

 This hot box was kept on  a bench  down a flight of step in a cellar that was always in total darkness  save for the few minutes I was down there.

The box lights were on 24/7 , as soon as a tray of seeds germinated ( checked first thing in the morning & at night ) , the tray was taken out the cellar into the conservatory ,which was shaded from too much sunlight.
  Due to the conservatory being on a north side of the home  it never got screaming hot during the day .
  The seedlings thrived here till planting out either in the polytunnel , in the main gardens till being potted up ..

 Once I left the germinated seeds in the hot box too long ( four days )  . They grew long and lanky very quickly , on getting them into the conservatory thus into day light they grew at the same rate as other plants of the same type but were still far too leggy for my liking . They never outperformed the other better grown plants .

 This year I have been experimenting again ( daily )  with the LED lit hot bed that is situated in an office that has little natural light getting into it. I've purposely  left some germinated seeds to grow on for another 14 days under the LED lights still with hot bed on at 19 oC to see what the result becomes .

The plants are not as leggy and lankas I'd expected then to be  but they are still  much longer & thinner than  germinated seeds that got placed  in the greenhouse at th earlier time .    So obviously something is helping them to grow on the LED hotbed (   heat , correct  moisture  & nutrients )  .   Whilst there is a fair green colour to the pea leaves  they are not as green as the peas that were putout into the greenhouse the day I discovered the seeds had germinated .

landarch wrote: One rule I created for myself is that when any part of gardening becomes a burden I shut it down...it should be fun at every step.  .

I am adopting your rule, Landarch.

It does seem the information regarding lights is overly complicated and contradictory. My plants are up, green, and some are actually in the SFG.

Scorpio Rising wrote:

landarch wrote: One rule I created for myself is that when any part of gardening becomes a burden I shut it down...it should be fun at every step.  .

Agreed. At one time I was into model railroading and I remember a good article in one of the magazines. The title was something like "Moderation, a Good Thing in Model Railroading".

Mel designed SFG to be easy and fun and to require less time, less energy, less space, less weeding, less everything that was difficult with row gardening. I would like to keep it that way for myself. I need to examine what I am doing and make sure I stick with the moderation theme.

Trolley...funny you should mention model railroading.  A guest pastor at church this past Sunday talked about addictions...and how a he got a call from good friend's wife...seems as if her husband would come home from work, eat dinner, then spend hours and hours in the basement full of railroad models.

My wife nudged me, smiled, and mumbled something about my garden. 

My excuse is that work needs to be done in the spring...I can rest once everything is up and in.

Besides, Landarch, it's "exercise." (Shhhhh - don't tell anyone but your wife....)

There are numerous threads about grow lights and the quality of light from various bulbs. Use the search feature to dig for more threads.