Ideal hours for lights on

tam91 · March 7, 2011

So I've seen references to lights being on anywhere from 12 hours to 24 hours each day. I think it's pretty well decided that 24 is not a good idea, they need some dark time.

But how many hours of lights is ideal? I just picked a number, and have my timer set to 15 hours for now. What do you all do, and why?

ContainerTed · March 7, 2011

Well, if you have an Aero-Garden, the one we have is preset to 17/7 and is not changeable. Maybe we have the cheap model, but the fresh herbs are great during the "snow time".

I have plants under lights right now and I am set up for about 17/7. I've used this now for at least 3 years and have no plans to adjust it.

I use that setting for ALL seedlings I start and that includes tomatoes, peppers, herbs, cukes, beans, flowers and anything else that trips my trigger.

Them babies need some rest (nap?) time every day or they become real cranky. (Now where have I heard that before??)

Ted

HoosierDaddy · March 7, 2011

I have mine set to operate for 16 hours.

**nctomatoman** · March 7, 2011

I turn them on when I wake up and feed the dogs - 7 AM - and turn them off when I go to bed - typically near midnight.

dustdevil · March 7, 2011

The light setup, the distance, wattage, etc. all affects how long the light(s) are on. There is no magic number, but the color and growth of the seedling will let you know which way to dial it.

HoosierDaddy · March 7, 2011

DDevil makes a good point.

tam91 · March 7, 2011

Hmm. Ok, so no one answer.
I have 4 T12 bulbs per shelf, very close to the seedlings - maybe I'll go with 16 hours then as a first guess.

333.okh · March 12, 2011

I use CFLs in a Rubbermaid box. I have 2x6500K 26W, 2x3500K 23W, and 2x2700K 23W bulbs. I keep them on 24 hours until the sprout emerge, then I back it off to 18 hours a day until they leave the cube.

amideutch · March 12, 2011

The tomato is a facultative short day plant which flowers and fruits earliest if the day is not extended beyond 12 hours by artificial light. Young tomato plants do not need the light intensities of full sunlight. Where there is no overlapping of leaves, light saturation is reached at intensities from 2000 to 3000 foot candles, or about one-fifth to one-third the intensity of direct sunlight at high noon. If artificial lights are used, an intensity of at least 500 foot candles should be provided at the leaf surface. Tests with fluorescent fixtures reveal that Wide Spectrum Gro Lux is slightly superior to cool white. Ami

jpop · March 12, 2011

Ami,
Are the wide spectrums (T-8) superior to T-5 high outputs (HO) as far as light spectrum for growth (both being 6500k). Looking into purchasing an assembly solely for seedlings and am curious as to what would fit my needs.

ddsack · March 12, 2011

Quote:

But how many hours of lights is ideal? I just picked a number, and have my timer set to 15 hours for now. What do you all do, and why?

I like to mimic close to a natural mid-summer daylight schedule, so my lights go on at 5:30AM and off at 10PM. 16.5 hours. I found a nice heavy duty timer for outdoor Christmas lights (on sale) to keep from having to trudge down to the basement every morning.

amideutch · March 12, 2011

jpop, really can't say. Here is the unit I built for my seedlings. I use 3 40 watt 48" Power Twist full Spectrum bulbs rated ar 5500K with a color rendering index of 91. And 6 26 watt full spectrum CFL's rated at 6700K with a rendering index of 98. It's sole purpose in life is to grow tomato seedlings which it does nicely. If I wanted to grow plants to term I have a 1KW halogen in the basement. Ami

tomakers · March 13, 2011

Just to answer the question.
I have used 16 hours for the last 20 years and it has always been fine. Initially I just went with a long summer day as the standard and it has always seemed plenty.
JMO,
Tom

amideutch · March 13, 2011

I think the answer is whatever works best for you. I go with 12-14 hours a day with my set up. Ami

lemurian · March 15, 2011

Like you I've read and read and never reached a solid conclusion about what is best. I do know from my limited experience so far that 12/12 gives much better results than 24 hours 7 days a week of solid light. I think the closer you can get to mimicking nature, the better off you'll be. Maybe having seeds under lights 24/7 until they germinate is fine, but to grow them I'd definitely give them a good 8 hours of dark at least.

March 7, 2011	#1
tam91 Tomatovillian™ Join Date: Aug 2010 Location: Crystal Lake IL Posts: 2,484	Ideal hours for lights on So I've seen references to lights being on anywhere from 12 hours to 24 hours each day. I think it's pretty well decided that 24 is not a good idea, they need some dark time. But how many hours of lights is ideal? I just picked a number, and have my timer set to 15 hours for now. What do you all do, and why?

March 7, 2011	#2
ContainerTed Tomatovillian™ Join Date: Jul 2008 Location: 6a - NE Tennessee Posts: 4,538	Well, if you have an Aero-Garden, the one we have is preset to 17/7 and is not changeable. Maybe we have the cheap model, but the fresh herbs are great during the "snow time". I have plants under lights right now and I am set up for about 17/7. I've used this now for at least 3 years and have no plans to adjust it. I use that setting for ALL seedlings I start and that includes tomatoes, peppers, herbs, cukes, beans, flowers and anything else that trips my trigger. Them babies need some rest (nap?) time every day or they become real cranky. (Now where have I heard that before??) Ted __________________ Ted ________________________ Owner & Sole Operator Of The Muddy Bucket Farm and Tomato Ranch

March 7, 2011	#4
nctomatoman Tomatoville® Moderator Join Date: Jan 2006 Location: Hendersonville, NC zone 7 Posts: 10,385	I turn them on when I wake up and feed the dogs - 7 AM - and turn them off when I go to bed - typically near midnight. __________________ Craig

March 7, 2011	#6
HoosierDaddy Tomatovillian™ Join Date: Jul 2010 Location: Zone 5 SE Michigan Posts: 50	DDevil makes a good point. Last edited by HoosierDaddy; March 8, 2011 at 06:26 AM.

March 12, 2011	#9
amideutch Tomatovillian™ Join Date: Feb 2006 Location: Germany 49°26"N 07°36"E Posts: 5,041	The tomato is a facultative short day plant which flowers and fruits earliest if the day is not extended beyond 12 hours by artificial light. Young tomato plants do not need the light intensities of full sunlight. Where there is no overlapping of leaves, light saturation is reached at intensities from 2000 to 3000 foot candles, or about one-fifth to one-third the intensity of direct sunlight at high noon. If artificial lights are used, an intensity of at least 500 foot candles should be provided at the leaf surface. Tests with fluorescent fixtures reveal that Wide Spectrum Gro Lux is slightly superior to cool white. Ami __________________ Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting ‘...Holy Crap .....What a ride!'

March 7, 2011	#5
dustdevil Tomatovillian™ Join Date: Jan 2010 Location: WI, USA Zone4 Posts: 1,887	The light setup, the distance, wattage, etc. all affects how long the light(s) are on. There is no magic number, but the color and growth of the seedling will let you know which way to dial it.

March 12, 2011	#8
333.okh Tomatovillian™ Join Date: May 2010 Location: NorCal Posts: 110	I use CFLs in a Rubbermaid box. I have 2x6500K 26W, 2x3500K 23W, and 2x2700K 23W bulbs. I keep them on 24 hours until the sprout emerge, then I back it off to 18 hours a day until they leave the cube.

March 12, 2011	#10
jpop Tomatovillian™ Join Date: Feb 2011 Location: SE Florida Zone 10 Posts: 319	Ami, Are the wide spectrums (T-8) superior to T-5 high outputs (HO) as far as light spectrum for growth (both being 6500k). Looking into purchasing an assembly solely for seedlings and am curious as to what would fit my needs. Last edited by jpop; March 12, 2011 at 10:20 AM.

March 13, 2011	#13
tomakers Tomatovillian™ Join Date: May 2006 Location: Cranberry Country, SE MA - zone 6? Posts: 353	Just to answer the question. I have used 16 hours for the last 20 years and it has always been fine. Initially I just went with a long summer day as the standard and it has always seemed plenty. JMO, Tom __________________ I never met a fish I didn't like.

March 15, 2011	#15
lemurian Tomatovillian™ Join Date: Dec 2010 Location: Ida Grove, IA Posts: 55	Like you I've read and read and never reached a solid conclusion about what is best. I do know from my limited experience so far that 12/12 gives much better results than 24 hours 7 days a week of solid light. I think the closer you can get to mimicking nature, the better off you'll be. Maybe having seeds under lights 24/7 until they germinate is fine, but to grow them I'd definitely give them a good 8 hours of dark at least.