Since they're doing fine where they are, wait until frosts are over in May. The coleus should go out after nights are into the summertime range, in June.

Awesome, thanks bboy.

Think I need to stake the trees?

Violetta - I don't stake tree seedlings. I have put them out without hardening them off completely though, and set them back by at least 6 months. Unfortunately, they were tiny trees I had planned that year to give my sister on her birthday.

It's too early to put seedlings outside. And it's not just temps you need to get them acclimated to - the linked article explains the hardening off process so thoroughly, I hope you'll read through it.

Here is a link that might be useful: Bracing Up - Hardening Off

morz8, that was great and I thank you. I feel much less like I'm in over my head now!

The article referenced electric lighting vs. sunlight. These seedlings have never been under any electric lighting - they've just been in front of a south-facing sliding glass door. Does that mean anything in terms of the hardening off process?

No! Even your hottest, south facing window doesn't get the same kind of sun that plants receive from outdoor direct sunlight. I didnt read the article but hardening off is more then just light exposure. It's frosty nights on a plant that's been cozy in the house; a tender seedling that's been so warm it decided to put on some new growth way before all of the other tree have even broken buds outside.

That makes sense. Thanks, nwnatural.

Violetta, congratulations! Those baby trees are just the cutest!

Thanks estreya!

I actually noticed today that they were moving slightly whenever there was a breeze outside. Hadn't thought about it before, but I guess my insulation by that sliding door is pretty awful!

I moved them so that they're in front of the part of the door that opens. Since it's so beautiful out right now, they're getting sunlight and a breeze even though it's too early to actually move them outside. :0)

With your green thumb (clearly, you have one), i'm sure they'll adjust to the outdoors just fine when you do decide to move them. Meanwhile, just everything seems to be turning towards the sun. Even my aging cat, who hobbles along now, relished in frequent sun baths today, moving from sun-patch to sun-patch as the light shifted in the rooms.

Good luck with your babies. And do take pictures to share with us often as they grow and grow and grow ...