We haven't had a hard frost yet, but it's coming. Is it time to trash the tropicals? Jack Frost will decide if you don't, once the temperature dips below freezing.

While many non-hardy plants -- osteospermums and million bells or calibrachoa, for instance -- will tolerate a light frost, you'll lose them to a hard freeze.

True tropicals, plants that are native to zones 9 and above, can't abide anything below 20 degrees for extended periods.

These hotties are perennials but are grown as annuals in our zone since they perish over our winters. Unlike annuals, which must be planted from seed each season, tropical perennials, given warm temperatures, can last for years, just like our temperate perennials.

But unless you have a greenhouse or solarium where these can be grown until warm temperatures return, you'll have to find a place to snooze them -- or lose them.

Cold frames, heated garages or porches, the inside walls of unheated garages and attics, cool basements and freeze-free crawl spaces all offer options for many of these plants. Some need a modicum of light (a basement window or grow lights), while others can be stored in darkness.

Those that don't need light may be coaxed into dormancy for the winter. Since many of these grow in containers, I often leave them in their pots (cut off the foliage and stack them to save space); or store them in insulated picnic coolers.

Some tropicals, like hibiscus and gardenias, if given good light, do their time as handsome and decorative house plants, blooming on and off over the winter. (Keep it cool at night for the gardenias.)

Below are a few of my own winter "boarders" and what they require:

Mandevillas: Like many other tropical vines, Mandevillas are speedy growers, putting on seven to 10 feet per season. They are hardy to Zone 9, so they don't survive steady temperatures much below 55 degrees F.

You have two choices: Keep them going as a houseplant; situate them in a sunny, south facing window and water once a week. These are light-sensitive plants and will not bloom through the short-day winter months unless you supplement their lighting. The plant may also go dormant and lose its leaves, even if you do add lights. Should that happen, keep it on the dry side.

Your other option is to move this potted vine into a sheltered area of a garage or shed. Trim the plant to a foot or so and store it in an area (crawl space, basement), where the temperature stays about 55-60 degrees.

Don't fertilize over the winter and keep the soil on the dry side. Once spring arrives, move to a sunny indoor spot, pinch new growth as it appears to form a bushier plant, repot and fertilize. Keep it indoors until Memorial Day, unless temperatures consistently stay above 60 degrees.

Brugmansia or Angel's Trumpet: These great plants have huge and fragrant trumpet flowers, but they can grow large. (They are small trees in their native environment!) Potting in a large container and hard pruning keeps them in bounds. Winter these the way you would a Mandevilla: in a cool place or as a houseplant. Water sparingly once the plant goes dormant and loses its leaves, and once new growth appears in spring, start fertilizing. Wait until warm weather to bring it back outdoors.

Agapanthus: There are a number of varieties of this Lily of the Nile, including miniatures, and some are hardier than others, surviving outdoors with a heavy mulch cover.

I've got mine in pots, which I winter over in a cool, non-freezing crawl space that gets minimal light. Cut them back as the foliage dies, and water lightly about once a month.

If you need a good-looking foliage plant, these make great stand-ins with their glossy, strappy foliage. Given good light, they may even bloom.

Phormiums: These handsome, spikey foliage plants stay potted at the back wall of my garage. I water them when I think of it -- several times a winter -- and make sure they get some light. If you've got a sunny spot indoors, enjoy them there.

Geraniums: I love the herbal varieties with their scented foliage, but they grow large by summer's end. Although they do flower, it's the fancy, cutwork leaves which smell like lemon, cinnamon, clove and so many other herbs that keep me growing these.

I take cuttings and start smaller, more manageable plants for indoors. As for the Pelargoniums, the geranium's well-known cousin, I simply cut them back and leave them in their containers in the attic; I've also hung the plants by their roots in a cool, dark cellar.

Replant in spring, water and fertilize after removing any dead areas, and move to a sunny window before taking outdoors.

Short on storage space? Take cuttings of half hardy perennials you like, root them in water or soilless mix, and start new plants. Coleus and Plectranthus (root in water), of which there are many, make good houseplants.

P. hilliardiae: With its purple-backed foliage and lavender spikes (which bloom most of the winter) , this is a winner indoors and out, almost 12 months of the year.

Coming up

Visit the Haunted Pumpkin Garden (through Oct. 31) at the New York Botanical Gardens and "Kiku: The Art of the Japanese Garden" (Friday, Oct. 5--Sunday, Oct. 27), with magnificent displays of chrysanthemums in its Enid A. Haupt Conservatory. Details: www.NYBG.org

Fall Afters Program at the Garden Education Center of Greenwich: Wednesdays through Wednesday, Dec. 18, K-thirdrd Grade, 3:30-4:45 p.m. Classes that follow the seasons, nature hikes, harvesting crops, building teepees, planting bulbs and more. Details: www.gecgreenwich.org or 203-869-0242

The 2014 UConn Master Gardener Program is open to individuals interested in horticultural training to enable them to share knowledge with the community and expand their own gardening expertise; 14 class sessions weekly beginning in January at Bartlett Arboretum. Details and application: www.ladybug.uconn.edu/

Maureen FitzPatrick is a freelance writer in Connecticut; www.maurdude@aol.com.