Overwintering Cannas, Dahlias, Caladiums, Tuberous Begonias, and Elephant Ears
If you live in the colder part of the country, many lush, tropical plants will be tender in your Zone, unable to survive the winter. Often gardeners will simply grow these beautiful plants as annuals, just enjoying them for one season. But the serious plant enthusiast rises to the challenge and goes the extra mile to let these plants reach their full perennial potential. If you make the effort to overwinter your tender plants, you can enjoy an increasingly beautiful display every season, and your garden will be all the more elite for the inclusion of these exotic perennials.
One way to keep your tender plants growing is to keep them in a pot so that you can move them indoors or shelter them in a greenhouse. This option is easy and convenient, and lets your plants continue to slowly grow throughout the winter, but a greenhouse also involves some start-up costs and requires that your plants all be in containers. So follow these steps to replant perennials that are tender in your growing zone.
Wait until the bloom show has ended and the foliage has started to die off, towards the end of fall. Your plants will tell you when it is time by dying back and going into dormancy. Once your plants are done for the season, take a pair of clean pruning shears and cut back the foliage to just above the ground (about 6 inches, depending on the plant's height). This will give the plant a clear signal that the season is over and it is time to go into dormancy, if it hasn't already. It is important to use a clean pair of shears to avoid introducing rot—rot is your biggest enemy throughout this process, so clean your shears with alcohol to be extra careful.
Now you are ready to dig up your tuber. Move about a foot away from the crown and dig down deep to get underneath of it. Be careful not to pierce the tubers, because again that can promote rot. Circle the plant, loosening up the soil, and then gently lift it out of the ground. Rinse off any remaining soil until you can see all the tubers hanging from the stalks. Cut off any tubers that look rotten, to keep the rot from spreading.
Next it is time to divide up the plant. This will help it grow healthier next year, and it means that you get more specimens to grace your garden.
First identify the eyes—these can vary from species to species, but they look similar to the eyes of a potato, and this is where new growth will come from next year. Cut up the plant into segments, trying to leave the individual tubers as intact as possible, and make sure that each division has at least one eye.
Now set the tubers out to dry. Leave them out at least 3 days until they are thoroughly dry. Placing them on cardboard can help. Getting the tubers dry will prevent them from rotting.
Lastly, you want to put your dried tubers away for the winter. A cardboard box, wooden box, or basket are all great storage places, as they allow some ventilation. Place the tubers in a medium, like wood chips, sand, or vermiculite, which will insulate and help to prevent rot. This medium should be just slightly moist to keep the tubers from drying out too much over winter.
Then place your box in a dark, cool place (50 degrees at most, 35 degrees at the least) over winter. A cellar, garage, basement, or even dark closet might work—if all else fails, set a small refrigerator to 45 degrees and store your overwinter plants there. Don’t forget to label your box so you know what varieties are in it. Check in on your tubers just a few times throughout the winter to make sure they are not rotting or getting too shriveled up. A little bit of shriveling is normal, but if they seem very dry, give them a spritz of water. Remember that the tuber stops "drinking" during dormancy, so they just need a small amount of water to keep them from completely drying out. And if you see signs of rot, throw those tubers out.
That is all there is to it. Next spring you should (fingers crossed) have more healthy plants than ever before, ready to provide you another long season of beauty. You can also get the jump on the season by starting your plants indoors about a month early. Start with a few hours of indirect sunlight and let them adjust slowly to light again before you plant them out.