Garden Detective

Technically a vine, Mandevilla often is grown in a large pot and allowed to climb on a trellis. It thrives outdoors in partial sun. For overwintering indoors, it should be brought inside in early autumn, when daytime temperatures dip into the 60s. In late spring, when temperatures consistently reach the 70s, Mandevillas can be moved outdoors for another season. But what to do in between?

You have two options: Allow the plant to go dormant, or try to keep it going over the winter.

To go the dormancy route, after moving the plant indoors in September, you should set it in a warm spot (68 to 70 degrees) in indirect sunlight and keep the soil consistently moist. It's normal for Mandevilla to drop leaves in October or November, so don't panic when that happens. That's the time to prune it and to move it into a cool (50-60 degree) spot. Over the winter, water only when the soil completely dries out.

In late winter or very early spring (now), move the plant back into the main part of the house near a window that offers indirect light. Pick up the watering again and apply a balanced fertilizer (10-10-10 or 20-20-20) monthly until fall. The plant will leaf out soon.

If you choose to keep it as an active houseplant over the winter, it will survive, but don't expect it to be pretty: It probably will lose some leaves and it won't bloom much.

In either case, move it back outdoors gradually around Memorial Day, beginning with a half-hour a day and working up to 8 hours over the course of 10 days or so.