The photo of the Elephant ears plant above is from a neighbor's garden. Last year in the spring she asked me to help her plant the spring bulbs she bought for her garden. Later as the growing season was ending and I was helping her clean out her flower bed I decided to leave the Elephant ears in the ground and see if they would survive a winter in Chicago. As the photo of the plant's foliage shows they did indeed survive a winter in zone 5 and they did so without the aid of mulch.
"I'm brave with other people's plants."
When I decided to conduct this little experiment I was guided by two factors. Like I mentioned in the post Outdoor Gardening With Houseplants-I have a serious case of zone denial and I was playing with plants that weren't mine. Also, Elephant ears corms are easy to come by in garden centers and you can purchase these corms for between 2-10 dollars (US) in big box garden centers. If you're a frugal gardener you may already know that you can purchase "taro" or "coco yam" root (Colocasia esculante) in Asian grocery stores for a few cents per pound and grow it instead of eating it. It is one of many plants you can grow in your garden that you can purchase from your grocery store.
"Why I think it worked."
The reason I think these tropical plants survived the winter in the ground in Chicago is twofold. This particular garden is in full sun all year round so I'm theorizing that the garden bed freezes later in the winter and warms earlier in the spring. This portion of the garden is also up against a stone/brick building as you can see by the photo. The horizontal line where the brick begins is actually the ceiling of the "garden apartments" next door. The building's stone foundation trapped and retained (heat from the sun) coupled with the energy loss from heating the apartments over the winter and the full sun location allowed the Elephant ears to survive the winter.
"Maybe it was just a fluke/OMG, Al Gore is right!"
It certainly is possible that the survival of these tropical plants is just a fluke and by no means am I saying that Elephant ears are now perennials in zone 5 gardens. Feel free to disagree in the comments section. But in the same spot and under the same conditions Dahlia tubers (USDA zones 7-11) and Gladiolas corms also survived. I should note that Canna rhizomes did not survive in this spot but did overwinter just two houses down in a raised bed made out of bricks, I think the Cannas died because I didn't plant them deep enough. I'll take a couple more pictures and continue this part of the post on my Garden Hacker blog in a few days.
Perhaps Global Warming played some part in the process after all the Arbor Day Foundation placed Chicago in Zone 6 in their 2006 Hardiness Zone Map. The USDA Hardiness Zone map does not yet reflect the same change. Then there is the phenomenon of Urban Heat Islands- this could aide a plant's ability to survive a winter in a Chicago garden but fail to survive the same winter in one of our suburbs. There is also the possibility that we had a below average winter-but in my own garden the Kniphofias (Red Hot Pokers) I purchased that were labeled hardy to Z-5. But I don't have full sun exposure in my garden or the benefit of a heat trapping and emitting structure next door and I forgot to mulch them.
The next time you come someone digging out their Elephant ears or see them for a really good price pick them up and experiment with them if you urban garden or have similar conditions where you live.