Grow Lights

Plantersville · December 29, 2011

Just wondering what some of you do with grow lights. Do you leave them on 24 hrs a day or just like leave the on for about 20 hours or 12 hours per day?
Thanks for any input!

Gobig_or_Gohome_toms · December 29, 2011

I set them on a timer for about 16 hours a day. Give them them night time to do what is typically natural to them.

Craig

Worth1 · December 29, 2011

16 hours a day
Worth

Fusion_power · December 29, 2011

You can leave plants under grow lights 24/7 but it actually suppresses growth. Plants need a photo period to accumulate sugars and a dark period to expend them in growing.

My light stand holds 36 fluorescent 4 ft bulbs and can accomodate up to 30 standard trays 11" X 22" at a time. I usually turn the lights on and leave them on for about a month when I start tomato seedlings. I have up to 60 trays of plants and every 12 hours I swap the 30 trays that are under the lights with the 30 trays that are sitting on top of the lights. There is a big reason for handling each tray this many times. It allows me to look at every cell and seedling to see what is going on with the plants and from holding the tray I can tell if water is needed. I can handle the plants this way and totally avoid over watering or under watering either of which can kill thousands of seedlings in a matter of hours.

Once the seedlings are about 4 inches tall, I move them to the greenhouse and transplant into individual trays of cells. This is a fairly efficent way to produce about 50,000 seedlings in a year.

DarJones

Plantersville · December 29, 2011

thanks folks for that helpful info..........

DarJones, good idea about putting trays above the lights........Im gonna try that!

OtterJon · December 30, 2011

I have mine (Ceramic Metal Halide 400w) on for 16hrs on/8hrs off seems to be about right.

Jon

Hastings · December 30, 2011

Can you use a full spectrum tube light? Or what works best to grow seedlings for artificial lighting, keeping cost in mind.

bcday · December 30, 2011

You can use a full spectrum tube if that's what you have. If you're buying new tubes and only using them for a few weeks to grow transplants, the cheaper cool white/warm white tubes work just as well. No need to buy pricey full spectrum tubes.

tgplp · December 30, 2011

This isn't scientifical or fancy but... I turn them on when I wake up and off when I go to sleep.

plants do fine like that for me.

Taryn

erlyberd · January 7, 2012

I typically leave my cheapo, twin bulb, shop lights, with two cool white bulbs on for 8-10 hours a day and produce nice healthy seedlings. This is in a room that gets some natural light if it makes a difference. Also, I keep the bulbs 2-4" off the top of the plants. I normally grow my seedlings inside under these lights for 3-4 weeks and start moving them outdoors to gradually harden off.

Skaggydog · January 11, 2012

16 on 8 off to vegetate, 12 on 12 off to flower

bobberman · January 11, 2012

I got the best timer at Lowes that has 48 1/2 timers in it with 4 plugs. They were originally $12 and reduced to $9. I bought one and got it for $5. I liked it so much I went back and bought 2 more. I then decided to get two more and when I went backthey were reduced to $2.50 so I now have 8 total! Ican set a half hour for midnight and again 1 am and 2 am ect and its simple! Its mechinical just lift a tab. I set my fan in the greenhouse for noon 2 pm and 4 pm half hour each time! I can hook 4 plug or 4 fans! I even have a 200 watt mini heater set on one of the timers to heat for a half hour 4 times after midnight on cold nights!

SEAMSFASTER · January 12, 2012

I start my seedlings on a 2-tray Seedling Heat Mat with humidomes and blankets for extra insulation. As soon as the first seedling emerges, I transfer the tray to a custom-designed frame with two 40W T12 cool white bulbs set <2" above the top of the tray. I leave them there with lights on 24 hrs. per day until I estimate that at least 90% of the seedlings that will germinate have germinated.

During the very early phases, I've found it beneficial to have continuous light so that seedlings will have good light whatever time of day they decide to break the surface. This has really helped me to avoid growing pale, leggy seedlings.

Once I've completed the germination phase, I move the seedlings under 400W metal halide lights, which I have set on timers (of the type bobberman describes) for a 16/8 pattern. I use a fan to help strengthen stems. [The metal halide lights were rescued from the trash - too pricey for me to buy new.]

I recall reading somewhere that tomato seedlings can do fine with up to 20 hrs. of light per day, but really need that dark phase, as mentioned. In contrast, pepper seedlings do just as well without a dark phase.

As soon as outdoor temperatures get into the 50's I start hardening off, but I try (not always successfully) to not expose tomatoes and other heat-loving types to temperatures under 50°.

I agree that the cheapest tubular fluorescent lights can perform adequately if kept very near the surface of the tallest plants in a tray. Just today I purchased several more cheap-o fixtures for about $12 each, including the two bulbs!

A cost-benefit analysis just did not justify spending the extra $ for the more energy-efficient T5 bulbs. T5 bulbs cost >$8 each around here and the fixtures are about triple what I paid for the cheap-o T12 fixtures. It would take a decade or so to make up the difference in energy savings.

Metal Halide setup:

amideutch · January 12, 2012

This was taken out of the book "Greenhouse Tomatoes, Lettuce & Cucumbers" by S.H. Wittwer & S. Honma.

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.
Hope this helps. Ami

basilboy · January 12, 2012

Hi All,

I am growing some micro varieties of both tomato and peppers. I am also growing basil, oregano, and stevia. I am using High Output fluorescent fixtures on metro chrome shelving. I have my timers on 18 hours off 6. Is this too much? I want to add more to my operation but am also trying to balance my electric cost. If you have brighter lights can the number of hours be reduced? Thanks !

---
I am here: http://maps.google.com/maps?ll=44.970840,-123.013936

December 29, 2011	#1
Plantersville Tomatovillian™ Join Date: Feb 2006 Location: Plantersville, Texas Zone 8 Posts: 138	Grow Lights Just wondering what some of you do with grow lights. Do you leave them on 24 hrs a day or just like leave the on for about 20 hours or 12 hours per day? Thanks for any input! __________________ Chuck I love to eat, sleep and fish........not necessarily in that order!

December 29, 2011	#5
Plantersville Tomatovillian™ Join Date: Feb 2006 Location: Plantersville, Texas Zone 8 Posts: 138	thanks folks for that helpful info.......... DarJones, good idea about putting trays above the lights........Im gonna try that! __________________ Chuck I love to eat, sleep and fish........not necessarily in that order!

January 11, 2012	#12
bobberman Tomatovillian™ Join Date: Dec 2011 Location: Latrobe Pa. Posts: 142	I got the best timer at Lowes that has 48 1/2 timers in it with 4 plugs. They were originally $12 and reduced to $9. I bought one and got it for $5. I liked it so much I went back and bought 2 more. I then decided to get two more and when I went backthey were reduced to $2.50 so I now have 8 total! Ican set a half hour for midnight and again 1 am and 2 am ect and its simple! Its mechinical just lift a tab. I set my fan in the greenhouse for noon 2 pm and 4 pm half hour each time! I can hook 4 plug or 4 fans! I even have a 200 watt mini heater set on one of the timers to heat for a half hour 4 times after midnight on cold nights! __________________ Frank the Bobberman & Carpet Installer Inventor of the Bobber With A Brain,. Gadening, Greenhouse, Fishing, Softball, Scrabble. Single looking for a woman with a 100 acre farm!

January 12, 2012	#14
amideutch Tomatovillian™ Join Date: Feb 2006 Location: Germany 49°26"N 07°36"E Posts: 5,041	This was taken out of the book "Greenhouse Tomatoes, Lettuce & Cucumbers" by S.H. Wittwer & S. Honma. 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. Hope this helps. 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!'

December 29, 2011	#2
Gobig_or_Gohome_toms Tomatovillian™ Join Date: Jan 2008 Location: Zone 4 Lake Minnetonka, MN Posts: 967	I set them on a timer for about 16 hours a day. Give them them night time to do what is typically natural to them. Craig

December 29, 2011	#3
Worth1 Tomatovillian™ Join Date: Feb 2006 Location: Den of Drunken Fools Posts: 38,539	16 hours a day Worth

December 29, 2011	#4
Fusion_power Tomatovillian™ Join Date: Feb 2006 Location: Alabama Posts: 2,250	You can leave plants under grow lights 24/7 but it actually suppresses growth. Plants need a photo period to accumulate sugars and a dark period to expend them in growing. My light stand holds 36 fluorescent 4 ft bulbs and can accomodate up to 30 standard trays 11" X 22" at a time. I usually turn the lights on and leave them on for about a month when I start tomato seedlings. I have up to 60 trays of plants and every 12 hours I swap the 30 trays that are under the lights with the 30 trays that are sitting on top of the lights. There is a big reason for handling each tray this many times. It allows me to look at every cell and seedling to see what is going on with the plants and from holding the tray I can tell if water is needed. I can handle the plants this way and totally avoid over watering or under watering either of which can kill thousands of seedlings in a matter of hours. Once the seedlings are about 4 inches tall, I move them to the greenhouse and transplant into individual trays of cells. This is a fairly efficent way to produce about 50,000 seedlings in a year. DarJones

December 30, 2011	#6
OtterJon Tomatovillian™ Join Date: Aug 2011 Location: Michigan Posts: 218	I have mine (Ceramic Metal Halide 400w) on for 16hrs on/8hrs off seems to be about right. Jon

December 30, 2011	#7
Hastings Tomatovillian™ Join Date: Aug 2011 Location: Nebraska Posts: 81	Can you use a full spectrum tube light? Or what works best to grow seedlings for artificial lighting, keeping cost in mind.

December 30, 2011	#8
bcday Tomatovillian™ Join Date: Jan 2006 Location: NY z5 Posts: 1,205	You can use a full spectrum tube if that's what you have. If you're buying new tubes and only using them for a few weeks to grow transplants, the cheaper cool white/warm white tubes work just as well. No need to buy pricey full spectrum tubes.

December 30, 2011	#9
tgplp Tomatovillian™ Join Date: Jan 2011 Location: Pacific North West, zone 8a Posts: 510	This isn't scientifical or fancy but... I turn them on when I wake up and off when I go to sleep. plants do fine like that for me. Taryn

January 7, 2012	#10
erlyberd Tomatovillian™ Join Date: Jan 2011 Location: CT Zone 5 Posts: 186	I typically leave my cheapo, twin bulb, shop lights, with two cool white bulbs on for 8-10 hours a day and produce nice healthy seedlings. This is in a room that gets some natural light if it makes a difference. Also, I keep the bulbs 2-4" off the top of the plants. I normally grow my seedlings inside under these lights for 3-4 weeks and start moving them outdoors to gradually harden off.

January 11, 2012	#11
Skaggydog Tomatovillian™ Join Date: Jul 2011 Location: Southern California Posts: 131	16 on 8 off to vegetate, 12 on 12 off to flower

January 12, 2012	#13
SEAMSFASTER Tomatovillian™ Join Date: Jun 2010 Location: American Fork, Utah Posts: 160	I start my seedlings on a 2-tray Seedling Heat Mat with humidomes and blankets for extra insulation. As soon as the first seedling emerges, I transfer the tray to a custom-designed frame with two 40W T12 cool white bulbs set <2" above the top of the tray. I leave them there with lights on 24 hrs. per day until I estimate that at least 90% of the seedlings that will germinate have germinated. During the very early phases, I've found it beneficial to have continuous light so that seedlings will have good light whatever time of day they decide to break the surface. This has really helped me to avoid growing pale, leggy seedlings. Once I've completed the germination phase, I move the seedlings under 400W metal halide lights, which I have set on timers (of the type bobberman describes) for a 16/8 pattern. I use a fan to help strengthen stems. [The metal halide lights were rescued from the trash - too pricey for me to buy new.] I recall reading somewhere that tomato seedlings can do fine with up to 20 hrs. of light per day, but really need that dark phase, as mentioned. In contrast, pepper seedlings do just as well without a dark phase. As soon as outdoor temperatures get into the 50's I start hardening off, but I try (not always successfully) to not expose tomatoes and other heat-loving types to temperatures under 50°. I agree that the cheapest tubular fluorescent lights can perform adequately if kept very near the surface of the tallest plants in a tray. Just today I purchased several more cheap-o fixtures for about $12 each, including the two bulbs! A cost-benefit analysis just did not justify spending the extra $ for the more energy-efficient T5 bulbs. T5 bulbs cost >$8 each around here and the fixtures are about triple what I paid for the cheap-o T12 fixtures. It would take a decade or so to make up the difference in energy savings. Metal Halide setup: