Question
I received a beautiful red Mandevilla as a gift last Spring. It flourished outside all summer, blooming profusely. I just brought it in, but am afraid it did get hit by frost. It doesn't look very good. Will it survive or have I killed it? The leaves a mostly dry, if I trim it back could it come back, do you think?

Answer
Hi Alane,
  Mandevilla can tolerate temperatures as low as the high 40s for short periods of time.  If the plant did get exposed to a light frost just once then most of the damage will likely be done to just the leaves.
Winterizing Mandevillas call for cutting the plant back dramatically anyway so removing the damaged leaves should not cause a problem.
To prepare Mandevillas for the winter start with very lightly fertilizing. A liquid fertilizer is best. Dilute the fertilizer 1 part fertilizer to 2 parts distilled water (this is a good mix for fertilizing all houseplants). If you use fertilizer crystals then mix the fertilizer according to the directions on the package then dilute the mixed fertilizer the same as for liquid fertilizer.
Next cut the plant back to about 12 inches above the soil line. If you would like, you can propagate the vines/stems that have been removed so that you will have more than one Mandevilla next summer. Cut the vines/stems into cuttings that are about 6-8 inches long. Remove the bottom 2-3 leaves (at the cut end). Be sure to leave at least 3-4 leaves at the tip of the cutting. Dip the cut end in rooting hormone and place in distilled water. Once the new roots are about 1 inch long then transfer the rooted cuttings into fresh potting soil.
Also be sure to check the plant carefully for any insects, mites or other pests that may have gotten on the plant during the summer.
Place the pruned plant in a place where it will get as much as light as possible.
Maintain the plant on the dry side during the winter. Allow at least the top 1/3 of the soil to dry between watering. Just be sure not to allow the soil to dry out completely.

In the spring when you move the plant back outside, the new growth the plant produced over the winter may burn off. This is normal and will not harm the plant. The plant will soon start producing new growth and become the full flowering plant that it was this past summer.

I hope this helps. If you have any questions or need additional information please don't hesitate to ask.
          Thanks
              Tracy