The only way I've successfully propagated mandevillas is by layering them on the ground they way I would with an azalea. I grow mine in pots and do sink some into the ground. When I lift them in Oct I just slice the roots that have grown through the drainage holes and cut back the foliage. You can probably prune the plant back and dig up a good sized root ball. Put it in a pot and winter it over inside. I cut back on watering and don't feed them at all over the winter but they are kept under HID lights. They do well and even bloom sporatically throughout the winter but they are susceptable to mealy bugs and spider mites while inside.
Karyn

Thanks Karyn --

I guess I have nothing to lose by trying to dig them up and put them in pots for the winter. They'll certainly die here. I had purchased them as annuals, but now I don't want to part with them! :-)

Between digging them out and trying to get cuttings, hopefully I can keep this plant going. I overwinter a lot of things in our sunroom -- doesn't get all-day sun, but it gets enough for most things to make it (actually, last winter, my tropical milkweed kept blooming all winter!)

Thanks!

:-) Mel

I have overwintered Mandevilla for two years just by putting it in the garage, cutting it down to the soil in the pot and letting it go dormant. It comes back when the weather gets really warm. The only trouble is that these vines flower MUCH later than the ones you can buy in the spring that the nursery has forced. I have just about decided to buy them new each year so they will flower longer.
Betsy

I am a newcomer to this site and probably can't give you as much helpful info as the previous entries, but I also love this particular vine!! I have 3 (my first year for growing them) that are potted that I have been keeping outdoors and plan to bring indoors to winter over, as the others have recommended. I noted that we are both in the same planting zone (I'm in Michigan), so I am interested in how well we both will do with the cold weather. My problem is that I just purchased ANOTHER ONE, as it was so beautiful and I could not pass up an $8 purchase- I don't know if it will survive a transplant (wish me luck!!). Good luck & let me know how yours winter over. If I learn any tips, I'll pass along to you.

I'm going to try allowing a couple of my mandevillas to go dormant over the winter this year. I'd always kept them going under lights but I'm getting too tight for space so I'm going to keep the larger ones in an unheated GH that stays above freezing. I hope they make it.
Karyn

Glad I found this thread. My mom just asked me today to ask about mandevillas as she has one potted outside; she wondered how far back she could prune it before bringing it inside. She's never pruned it before bringing it in and noted it took so long for it to bounce back each year. Now I see by westview's post that this is apparently just the way it is and she'll have to put up with it if she wants this particular mandevilla!

She has brought it in every year for around 3 years now and it goes in the basement in front of sliding glass doors (with all of her other brought-in plants) so it gets light but no direct sunlight. She says hers has bloomed down in the basement as well, but it has always been slow to bounce back when it goes back outside in the spring.