I have brought my Mandevilla in for the winter. I've cut it back to a foot tall but now all the leaves are turning yellow and falling off. It faces a southern exposure and is sitting in a bay window. What am I doing wrong?

Thank you,
Kathy

I was hoping to see just exactly what to do to Winterize my Mandavilla on this web site. (only my plant is the small flower variety and is called something like Dipladenia)
What I remember reading or hearing is to bring it in before the first frost and either leave it to shead it's leaves or cut it back. All the leaves will go yellow and fall off if you don't cut it back. What a mess either way. The liquid that comes from the vines is like Elmer's Glue.
Keep the plant in a cool dark place above freezing. Water once a month but only slightly.
This Tropical plant needs not only full sun in the summer but doesn't necessarily need a lot of water. That is what I love about this plant! I have it in my very sunny back yard in a hanging planter. The only time I water it is when we haven't had rain in two weeks. NO KIDDING! When I bought my first one it was sitting in the full sun at the nursery on the BLACKTOP DRIVE!
So I cut mine back today pretty severly and I'm going to leave it in my basement. I may put a paper grocery bag over it. In the spring I will set it out on warm sunny days with a little moisture and hope for the best. Naturally, I will have plan B......Visit the Nursery or WalMart and buy a new one.