By Lindsay Bond Totten
Scripps Howard News Service

Wave "aloha" to those trendy tropicals that looked so great all summer in the perennial border. Jack Frost is about to remind us that they were simply "on loan," not ours to keep. Unless ... I know what you're thinking. It's too much trouble to dig them all up and store them indoors. Besides, there's not enough room in the house for all those pots.

OK, so go ahead and compost most of them. No need to bother trying to save annuals like geraniums or castor bean. They're so inexpensive or so quick to grow from seed that it doesn't make good use of precious time and space to overwinter them. But what about the costly banana tree? And the angel's trumpet that bloomed all summer on the deck? That special variety of New Zealand flax was $35, and not much more than a shoot when it arrived in the mail last March. Starting from scratch would really set you back.

You don't need a greenhouse or even a space indoors to overwinter some of your valuable tropicals, though you might enjoy keeping one or two as houseplants during the dark winter months. The tougher ones can be stored in a state of "suspended animation" that will bring them through the winter -- just barely, in some cases -- to grow and bloom another season.

The hitch is to find a place that gets cold, but not too cold. Under such conditions, a gardener coaxes the foliage of hardier tropical varieties to go dormant without letting the roots freeze. Not many houses have root cellars anymore, but if you own one, that would be a great place to try storing these semi-tender plants. A cool, dark basement, a minimally heated garage or potting shed or an enclosed porch are other options. Daytime temperatures should stay between 40 and 50 degrees F., with nighttime temperatures consistently above freezing.

Hibiscus trees, angel's trumpet (Brugmansia spp.), New Zealand flax (Phormium tenax) and mandevilla vines are popular tropicals worth trying to overwinter in this fashion. Banana trees (Musa spp.) and citrus trees like it slightly warmer -- they're also good candidates for houseplant status -- but they'll start right up in spring after a winter's rest.

My husband and I are fortunate enough to have a root cellar (one of the perks of owning an old farmhouse). Our brown turkey fig bushes get carried into the cellar each October, where they fare well in all but the most severe winters. They look a little shell-shocked when they emerge the following April, but the plants recover quickly as the new buds swell.

A number of tropicals worth saving produce underground tubers or bulbs that can be "harvested" at season's end and overwintered as dormant roots. Storage conditions are similar to those described above. Try this with cannas, caladiums and elephant's ears (Colocasia spp.).

Whether digging tropical plants or harvesting the roots, wait for several light frosts to singe the upper leaves. This sends a message to the roots to prepare for dormancy. If your tropical plants are already potted -- many gardeners grow them this way to avoid heavy digging in fall -- simply lift the pots out of the soil and hose them off. Carefully dig and pot those that are growing directly in garden soil. When the tops have blackened, cut the stems of herbaceous varieties, such as bananas, to within a few inches of the soil. Woody stems, Brugmansia, for instance, can be left "as is" to lose their leaves completely or pruned to save space. Don't cut woody stems back as hard as those of herbaceous plants. Wait to see what makes it through the winter, then prune back to live wood in spring.

Carry the pots into storage before the first killing frost. Check on them once a month during the winter and water lightly if the soil is dry several inches below the surface. If your storage area is in danger of freezing, protect plants with a thin foam blanket, available from greenhouse suppliers. It's worth a few degrees of insurance.

Dig tuberous plants after frost has killed the foliage. Cut off the stems and leaves and let the tubers rest and dry for several days. Some gardeners dust them with powdered sulfur to prevent rot during the winter. Store some tubers in mesh bags filled with lightly dampened peat moss, or layer them in flats. Check the peat moss occasionally to make sure it's still damp. Remove any tubers that have visibly rotted.

In spring, check frequently for signs that the plants are waking up. Acclimate them slowly to conditions outdoors and move them back inside if a late frost threatens. Our figs were killed once when a late frost claimed the breaking buds and plants weren't strong enough to put out another set of leaves.

(Lindsay Bond Totten, a horticulturist, writes about gardening for Scripps Howard News Service.)