Hi Bunyip- Welcome! :)
Sorry your post disappeared, don't know why it would! Where are you located? I live in Mooresville NC. 7b and successfully overwinter all of my brugs in-ground. My lowest temps last winter were 11*, and all of my brugs came back. I cut them down to 10 inches, covered a wide area over the stem with a deep mulch of leaves, and covered that with boxes stuffed with more leaves. This year, I will cover the stalks with wood chips. I think once they get to a good girth- over 1 inch, they will be strong enough to withstand subsequent winters. They come back stronger and bigger each year for me.I'm guessing since you can overwinter them in an unheated garage, (which is probably the same temps as the outdoors) that you can leave them in ground. I would plant them now, don't wait. When is your approx. first killing frost? I am still planting potted brugs in the ground and will cut them back and mulch them for winter. Of course, if you can plant them in a sheltered position, say, near a wall, that would give them a much better chance. Hope this helps!

Hi,Kasha! Thanks for the welcome and the information. I am very encouraged by it, and am definitely going to try. I think I will put the two biggest and oldest in the ground and keep the smaller ones inside this year, along with the white ginger and the mandevilla. Maybe I'll wrap the stalks with burlap stuffed with leaves and cover the lot with wood chips.

The ginger is flowering now and filling the garden with its intense honeysuckle scent and since it too is getting bigger I would love to put it in the ground, but I think it's too tender so it will have to put up with the garage again.

Not sure where you are located. If you are in 7a I'd take them in and allow them to go dormant. I've tried a number of times over the years to winter them over outside and they've never survived. I'm in MD, just outside of WDC, zone 7a. Hardy bananas do just fine here with a good mulching, there's quite a few in the neighborhood, not brugs. If you are in 7b/8a you should be able to keep them inground over the winter. If I was just a half a zone warmer. Oh well, in the garage they go.

I just re-read this and didn't realize that they were still in pots. You most likely want to bring them since they aren't already in the ground. I doubt there's enough time left in the growing season for them to develop a good root system. If you want to test their winter hardiness plant them in the yard next spring and leave them. I winter mine over in an unheated garage but raise the pots off the concrete floor.

Karyn and Kasha, thank you both so much for all the good advice! Given everything, I think I will keep the brugs in the garage again this winter -- it's partly underground so doesn't freeze in there, but stays around 45 degrees (provided people don't open the door and go away and leave it open!). Next year I will begin by planting a couple of the bigger ones in the ground for the summer, and maybe give one of them a try in the ground for the winter. Thank you both so much.

Your other thread didn't disappear; I just posted a pretty long answer there.

Rather than planting a big one in the ground next year, why not start a new cutting, so you don't risk losing one of your big ones?

Root it in water, and when has a little shock of roots, you can plant it in the spring when its humid and rainy, push the roots to one side, and stick the stem RIGHT up against the house where it will get constant warmth during the winter which might provide the extra couple of degrees it needs to survive. I don't think brugmansias are ever aggressive enough to damage foundations with their roots.

If you can find some nook or crevice between the house and a rock, deck, landscaping feature, etc, that will be all the better. The coldest times are at night, and heavy objects retain and slowly give off the day's heat during the night.

A few inches of mulch around the base (plus snowdrifts on top of the mulch) may give you one or two hardiness zones worth of heat in a micro-climate underground.

I'm in zone 5; gladiolus are supposed to be hardy to zone 7. They survive without being dug when they're up against the house. From zone 7, you could try it with brugmansias.