Updated 11/4/19
Hopefully by now you have brought in the majority of your tender succulents and tropical evergreens/gorgeous houseplants for the [presumably] long winter ahead. And hopefully by now, you have found room for them in living spaces that will soon bear the clutter of holiday decorating and higher-than-average persons per square foot.
Dealing with this chaotic shuffle every year makes me exceptionally grateful for the tender plants that retreat into a state of dormancy and can be held that way over the winter in garages, basements, cellars, and sometimes even a cold frame.
Canna rhizomes waiting for a plastic bag and garage accommodation. These have been rinsed, but it is not necessary and can sometimes encourage disease & rot.
These are the tropical or semi-hardy plants that grow incredibly quickly in our warm humid summers and might be yet decorating your garden with blooms, foliage and presence; but which will completely disappear for the winter into corms, tubers and rhizomes: plants like elephant ears, caladium, dahlias and canna. There are many others, but in the interests of simplicity and retention, we’ll concentrate here.
Why overwinter tropicals?
Now, if you’ve never dabbled, let me answer the [valid] question in the back of your mind: “Why grow plants that can’t live through my winter when there are those that can?!?” Certainly there is no need to dig and store a fully hardy Shasta daisy, but let me ask a question of you: Are your Shasta daisies adding anything to your landscape right now?
My cannas are still blooming and producing foliage, my ‘Lime Zinger’ elephant ear (Xanthosoma aurea) is still the centerpiece of my front garden, and when I go out to feed the chickens in the morning, I have a thirteen foot tall red banana on its third year (Ensete ventricosum ‘Maurelii’) that makes me feel like I’m a horticultural rock star.
By the end of the season, this ensete was two feet higher than the pergola. At the date of this post (11/4), and without a hard freeze, it is still going strong.
One must pick and choose. I find that it is usually plants that have strong foliage or a long season of bloom that tempt me to grow them. In the past I never overwintered caladium because I didn’t see a need to grow caladium. A garden tour in New York changed that for me. Ditto canna – though it was a different garden and a fascinating cultivar (‘Pretoria’) that turned my heart. I don’t grow and dig gladioli because I don’t happen to love gladioli. As of today, I remain cold-hearted on the issue and I put my efforts elsewhere. If you love what it does for your garden, it’s worth it. If not, don’t bother.
How to overwinter tropicals
First, let the frost deal with the foliage. It seems to be healthier for the plant (and easier for the gardener), if you allow a natural dieback here. I have never had a problem with this method, though I often see advice to pull them before frost. For ease of digging I do a rough chop of the stems at about 5-6 inches and then dig the rhizomes/corms (which are usually quite shallowly rooted).
With the exception of elephant ears (Colocasia spp., Alocasia spp., Xanthosoma spp.), I then like to remove the tubers/corms/rhizomes completely from the growing medium, cut off extra stems to about 1-2 inches, brush them lightly and inspect for any soft spots – cutting those out. In the past I washed them to see exactly what was going on, but was recently told by Brent Heath of Brent and Becky’s Bulbs that this can encourage disease and should be avoided. I don’t argue with Brent.
Sort them and make sure they are well labelled. We forget much over the winter.
I am fairly abusive towards my cannas, storing them in a big plastic garbage bag; but when it comes to dahlias and caladium I am more careful, putting them in a bag of lightly dampened wood shavings to keep them from becoming desiccated.
Not all of my elephant ears make a large corm that is easily removed and stored, so I leave them in the current season’s pot, stacked on a large wheeled cart that I can move around in the garage, leaving inspection and division for the spring. When I’m pressed for time, I deal with cannas similarly. Temperatures for storage in the garage vary, but are usually in the 40 degree range – perfect for the above.
Caladiums are a little different – they are the high maintenance friend in the group. They must be stored above 60 degrees – the bottom of a closet usually suffices. They also need a bit of humidity and air exchange, so it is important to go with the lightly dampened pine shavings route and check on them periodically.
These caladium are easily dug from soft container soil and placed in damp pine shavings in a closet indoors for the winter.
As it happens, I check on all of them periodically – adding a little water when things look excessively dry, and planting out only when the temperatures have significantly warmed or I have space in a cold frame. You won’t be successful with every single corm, every single tuber – but even an 75% survival rate is pretty good when you think of the cost of replacement.
If you think it might be worth it – experiment a little this year by overwintering a clearance canna and see how it works out. Trying something new can only make us better gardeners. – MW
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Reprinted with permission from The Frederick News Post
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