| These plants are not winter hardy in cold winter areas such as yours. They can be treated as annuals and replaced each year, or you can try to overwinter them indoors. Ideally, they would be moved to a heated and sunny bright greenhouse. If you want to keep them blooming as houseplants, they need to be brought indoors before the nights get too cold, say consistently below 55 degrees or so. Put them in a very bright location and keep watered and fertilized. They will stop blooming if the location is not bright enough or if they are exposed to too much cold before coming indoors. Alternatively, you can simply overwinter them indoors in a semi dormant state, leaving them outside until nights are in the mid-40's and then cut them back, bring them into a very cool (not freezing) bright room, water them just enough to keep the soil from drying out completely, and stop fertilizing for the winter. In spring when they try to grow again, water more and feed them and keep them in the brightest light as best you can. Yet another method is to leave them out later in the season as above, then place them in a cool location that is dark such as a basement or attached garage and hope they can survive; in this case they would be watered very little and eventually cut back hard and brought out into the light, and fed and watered normally again, in early spring. The switch from outdoors to indoors and vice versa should be done gradually to avoid shocking the plant and allow it time to adjust. Good luck with your mandevilla! |
