I usually give my tomatoes 12 - 14 hours of light...I transplant up as soon as they have a set of true leaves and then put them in my little greenhouse where they get good sun and cold temps at night...this makes them stockier...

How close do you have the light source to your tomatoes? It should only be about 2" to 3" above the tops of the plants...if the light source is too high the plants will stretch...

I run my lights 15 to 16 hours per day and keep the plants within an inch of the lights. The closer the better. Occasionally the plants touch the lights, but that has not caused me any problems.

16 hours a day. Light an inch or two above top leaves.

John

16 hours a day. I used to be a reef aquarium hobbyist so I'm using my lighting from that set-up: high intensity compact floresents 24" 65w bulbs x2. They run hot so it's about 4" from the top of the trays.

16 hours here, lights quite close to the leaves. I didn't see a mention of potting up. If you do that your plants will be stockier because you bury them to the leaves each time you pot up. I pot up twice, and my seedlings are fine. Nonetheless, when I plant out, they go deep into the soil.

I'm a using a 125 W grow light with a Ballast. I turn it on when I wake up and turn it off when I go to sleep.
I find the plants grow during the night too.

I give my plants between 11-14 hours a day, depending upon how sunny it is that day (since they are in a windowsill currently). Basically, if it's a nasty day, I give them a few hours of artificial light.

Every light in the house is on, the backyard's bright as the crack of dawn, the front walk looks like runway lights...

I have my light on a timer and run it 18 hours per day(we natrually get about 16-17 hours of daylight in the summer in my neck of the woods). I keep my light no more that 2 inches above the plants and the room is natrually cooler because of an insulation issue in that room. My pants are stocky and growing like crazy.

Larrick

I run mine 15-16 hours - b/c that's what my begonias need - works fine for tomatoes too! :)

Before I had lights I started them in a sunny window - they did get leggy, but it only lasts until you plunk them outside and they get over it quick.

"Every light in the house is on, the backyard's bright as the crack of dawn, the front walk looks like runway lights..."

haha...that's the second thing on Tomato forum that made me laugh this morning.

tn veggie,

I even have that link for you..

Here is a link that might be useful: Lights on...

I agree with all, however no one said anything about using a small osculating fan to move the air around? it really helps make the plants more stocky, I aim the air flow just above the plants so the leaves ruffle a bit when the fan blows the air there way.

mudflapper I have a small fan going as well. Not everyday but when I do I use it in 1-2 hour intervals. This season my seedlings are more stocky than before.

Has anyone run an experiment to see how many hours of darkness is ideal? I have one setup that only gets like 14 hours of light (because the lights would keep me awake), and one that gets 20 hours of light, but the fixtures and bulbs are different, so it's not a very good experiment.

I start my tomatoes in an unheated garage after solstice in Oregon. After the seedlings come up, I take them off the heat mat and use just the lights close and have a fan running to imitate wind. They are very stocky that way. I also bring the tray out on sunny days a few minutes and work up to more. When I pot up the the first leaves they go into an unheated green house and I open up the green house for a part of the day. They are very stalky that way.

It is not just the number of hours but also the intensity of light. If the light source is too high up, they will get much less. Having said that I also keep the lights on 12 to 16 hours.

Sey

Mine are in the kitchen. I flip the lights on in the morning as soon as I get up, flip them off on the way to bed so 15ish hours. I live in San Diego, so once they have true leaves, I put them outside during the day and bring them in at night.