Plants that are probably tough enough
In this group are perennials and shrubby plants like hardy fuchsias, hardy Windmill palm trees, hardy banana, yuccas and evergreen clematis. During a normal fall and winter they’ll all be just fine. But only if you remember not to get snippy with them or start pruning their foliage and make sure they are growing in a well-drained spot that does not have their roots sitting in water all winter.
I move my potted “Gold Band” yuccas under the eaves of the house to keep the soil somewhat dry during the winter. Don’t fertilize any of these marginally hardy plants in the fall. You want to encourage them to slip into winter dormancy so they can better battle the cold.
Newly planted evergreens such as azaleas, rhodies and viburnums may suffer wind burn or winter injury the first year but you can always snip off the damaged growth in the spring and they’ll grow tougher and more cold-tolerant each year they survive.
Plants that need a bit of protection
Summer blooming, tender bulbs such as dahlias, gladiolus, Pineapple lily or eucomis tuberous begonias and the new Dragon Wing begonias such as BonFire all need protection about now. Cut back the tops of dahlias, glads and begonias as soon as the leaves begin to turn yellow or once they are hit by a hard frost. Then you must decide to either dig in and save the bulb in a frost-free garage or basement, or just gamble a bit and cover the bulb, still in the ground with a tarp or other water-repelling strategy.
Some gardeners use the fronds of sword fern laid atop a bed of dahlias to keep out the winter rain. This works only if the soil is very well-drained. A raised bed, rockery or slope is the best way to ensure well-drained soil. Begonias need more protection from the cold than the others so after digging the tuber let it dry for a few days indoors. Then place it into a paper (not plastic) bag and store in a cool but not freezing garage or basement. Around the end of April you can repot your begonia tubers into potting soil but don’t take them outside overnight until all danger of frost is passed – usually mid May.
Plants that will surely die unless you do something
Geraniums, echeverias and other tender succulents, flowering maples or Abutilon and tropical plants such as bougainvillea, Mandeville and jade plants will all suffer and die when the weather turns frosty. Some gardeners in Western Washington have successfully saved these weaklings by placing them in a very protected location near the warmth of the house. (My grandfather enjoyed giant geraniums that survived three winters just by placing the pots on his covered and glass-enclosed porch.)
If you want to ensure that these tender plants survive you need to find a place indoors, away from cold drafts but with plenty of sunlight and just grow them as houseplants. This is not a pretty sight. The leaves will drop due to low humidity in the house, the plants will stop blooming and start reaching as they grow long and skinny looking for more sunlight. Your instinct will be to water and feed them more as they decline. Don’t do it. Give over wintering tender tropicals just enough water to keep them barely alive and do not fertilize. You really want to push the plant into winter dormancy indoors no matter how ugly it becomes. Then in the spring you can prune, pinch, feed and water right before setting the poor thing back outdoors for another go at blooming.
When all this fails you can just visit the nursery and buy a fresh and well-budded geranium or invest in another flowering tropical plant. Of all the tender plants to try and over winter, the Echeverias or tender succulents are probably the easiest to handle. They’ll still drop some leaves and stretch their necks but they don’t take up as much room nor look quite so unhappy as geraniums or flowering tropicals stuck indoors for the winter.
Marianne Binetti is the author of “Easy Answers for Great Gardens” and eight other gardening books. She has a degree in horticulture from WSU and will answer questions at binettigarden.com.