Should work fine, the big question isn't how cold it gets outside the garage, it's how cold it gets inside. If it's an attached garage you probably get a few degrees warmer regardless. Add in a little heat from the lights and you oughta be able to stave off actual freezing temps.

A space heater is a simple way to make sure on that, though. You don't have to turn it up enough to make it actually warm, just not freezing cold.

Folks have been doing this exactly like you are for a long time. On nice days you can open up the garage doors and bring the seedlings out for some sunlight. That's a good way to harden them off too.

Hey, if you want more light *and* heat, there are ample ways to kill two birds with one stone here ;) Pack the area full of lights and your seedlings will be thrilled. Just don't go overboard and fry them! :)

I have a garage setup, and I reverse the day/night cycle to provide extra heat at night and allow cooling during the day year round. Works well for me - I started tomatoes yesterday, but grow hundreds of other things continuously.

That does work, running the lights at night, but if you've got any windows or anything that lets light out your neighbors might get the wrong idea and think you're growing "something else".

Not everyone knows a tomato plant when they see it.

You're right - I get that question a lot. I'm kind of a boring guy, so I enjoy the notoriety. I'm tempted to grow a few cleomes, castor beans, or Hibiscus coccineus seedlings in there just to pique their curiosity, but I grow those outside, instead!

I hadn't thought of that, I might try that out myself. Unfortunately people would probably call the cops around here.

Castor beans are fun, I love those things. Definitely not an indoor plant, that one. Though I have given it as one... to someone I did not like at all.