Answer: Generally speaking, lantana is treated as a warm weather-only plant in cold winter areas such as yours. This means one would bring them indoors in the fall to overwinter in a greenhouse or a very sunny window. Since they have been outside until now, you may find that they have not only defoliated but also died outright due to the cold. If they were planted in the ground, the roots would have been better insulated than in an above ground container, especially if the container is a smaller one. At this point, you might try bringing them indoors and keeping them in a bright window, watering lightly, and see if they can manage to recover. In my own experience, an accidental overnight exposure to temperatures in the upper twenties, the plants did pull through although it took them some time to show any signs of life. They may eventually show growht on the stems or possibly even beginning from below the soil if all of the top growth was cold damaged. I'm sorry about your plants, but in all honesty it is just not reasonable to expect them to survive a Pennsylvania winter outdoors.
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