The following excerpt from a University of Vermont bulletin addresses your question:
"Most tender perennials prefer sunny and cool winters indoors. Mediterranean plants such as pomegranate and rosemary, citrus such as lemons and miniature oranges, and silvery plants such as lavender prefer sunny and cool winters. Some South African natives such as lily-of-the-Nile (Agapanthus) and annual geranium are in this group, as are the Australian hebes. Tropical "annuals" in this group include cigar flowers (Cuphea), summer snapdragon (Angelonia), and sages (Salvia). Many subtropical and tropical woody plants prefer sunny and cool winters, such as oleander, gardenia, osmanthus, and angel's trumpet (Brugmansia). Some such as fuchsia and hibiscus do well under these conditions as well as with sunny and warm, just with less growth.
Sunny and cool conditions can be provided in an unheated sunporch or guest room, minimally heated entry halls, or a cool greenhouse. Temperatures should remain between 45 and 55 degrees F ideally, or at least above freezing. These cool temperatures help prevent insect problems as an added benefit. The goal with sunny and cool is to keep plants from growing, or growing very slowly, most the winter. They are provided a rest period, and so are low maintenance.
Dark and dry conditions are needed for a handful of tender perennials, gladiolus corms being the most common. Some salvia in this wide-ranging genus can be stored here, unless they have formed tubers that should be stored damp. Similar to dark and damp, cool temperatures should range between 35 and 50 degrees F. "
Go here to read the complete bulletin:
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