How long do you keep your lights on?

I'm curious to find out how long most folks keep their lights on during seed starting. I had always heard 12-18 hrs/day but then recently read that 24 hrs/days was OK, too, so I've been experimenting with that this spring. The only seedlings I have of any size right now are morning glories and they look a little stunted to me. Is this because of too much light? I use 40w cool bulbs. I also have some tiny tomatoes that have just sprouted and they look fine at this point. Do you think I need to go back to less light?
Thanks!
Deb

24 hours a day is great if you are growing pot. Otherwise, 16 hours is good. Plants need time in the dark to put on a different kind of growth than they do in the light. I have tried leaving them on 24/7, and the growth is too lanky.

For most things eg petunias and tomatoes---they get 12 hours on and 12 hours off.
When I try to grow tuberous begonias from seed ---it is 6 hours on and 6 hours off.
12 hours of fluorescent light is about equivalent to 5 hours of sunlight.

16 hours.

I typically leave mine on for 16 hrs.

Thanks, all-I'll be setting up my timers today!

I also germinate my seeds at 14-16 hours a day. Now, the sun is warmer in my neck of the woods, literally, I'm germinating using DST (daylights saving time.)
Why burn the electricity when the sun will do the job as well or better.

I do alot using sunlight in the greenhouse after March 1st here (11 hours). Things can be a little slow to germinate if its cloudy but it still works great.

I keep my timer at 16 hours.

On a side note, my flats are in our cellar where it is cooler. My seedlings are growing albeit slowly and look good, but are still tiny. Is it because the cellar is cooler? I do not have enough heat mats for eight flats and certainly can't afford to buy seven more! Does anyone have any ideas besides moving my one heat mat around? I did the same thing last year and all of my started plants did well once they went outside. Any help?

I do my seed starting in my basement, as well. I have wondered the same thing about the cool temps. I find that when the lights are on, they generate enough heat to keep the shelves at 65-70 degrees, but I have a feeling that it drops down when the lights go off. I bought a plastic greenhouse enclosure for my shelf beause I thought it would keep the heat in, but to be honest, I haven't even taken it out of the box yet. There is a thread somewhere here on DG about making inexpensive heat "mats" using rope lights from Walmart. I'll see if I can find the thread for you-I'm thinking about trying to make a couple next year. On the other hand, I've read that you only want the bottom heat for germination, not for growth, because too much heat can make your seedlings spindley, so maybe in a cooler loation it's just best to allow a little extra time.
Deb

Here's that link-the part about the rope lights is towards the end (it's a very long thread):

( http://davesgarden.com/community/forums/t/683246/ )

This message was edited Apr 11, 2008 8:43 AM

Thanks for the link. I will look at it. Last year was my first year starting seeds. Have you had more experience in your basement to draw conclusions on?

This is a "new" basement for me and I have had a few problems getting things just right. It's very similar to my "old" basement (both 100 yr old houses with stone basement walls and very cool temps) and I had great success there. We built a little room out of wood for my plants at the old house because I had cats who liked to play in the dirt. In this house, I have no cats, but a stone "root cellar" type room that is not quite as closed in as the old one, I'm thinking the temeratures must be just a little lower here. Anyway, I'm working on it. Last year was a failure, this year I have some pretty nice looking tomato seedlings that are about 2" tall. I like starting in the basement because it's out of the way and I can spill dirt and water all over (at least in my basement!) and no one cares. It's almost as good as a greenhouse (but not quite . . .).

Your basement sounds similar to mine. My house is over 100 years old. I would call it more of a cellar than a basement. Let me know how yours turns out.