Over-Wintering Tropicals

Alocasia 'Polly' photo by Robert Weaver

By late September, I am readying my tropical plant collection for the indoors by trimming away dead or damaged growth, checking for insects and spraying, if needed, and inspecting potting soil for slugs and various critters.

By Chris Kelley

(This article was first published in The Gateway Gardener October 2006 issue)

It’s time to start dreaming big about your tropical paradise for next summer. Notes and images collected and logged this summer and fall by visiting the Missouri Botanical Garden, local nurseries, the colorful display beds at Meramec Community College, and, especially, the beautiful tropical containers and beds in Kiener Plaza downtown, will fill your winter dreams. Another ideal place to start is by over-wintering those ravishing, lush tropicals that have been summering on your patio. Many of these enchanting lovelies become friends, and it’s logical to want to nurture them through winter. When you return them outdoors next spring, you’ll reap the benefits of mature, hefty specimens for instant impact and gratification. Here are a few tips.

My over-wintering operation begins in September, as I set about making cuttings of  tropicals that I want to keep for spring cuttings. This is an effective and easy way for home gardeners to carry over favorite tender plants that can be costly to purchase every spring. By late September, I am readying my tropical plant collection for the indoors by trimming away dead or damaged growth, checking for insects and spraying, if needed, and inspecting potting soil for slugs and various critters. This done, I bring in my cuttings and very tender specimens first.

Storing growing (non-dormant) tropicals

If you’re unlucky enough, as I am, to be without your own personal Climatron, this is a plan for storing, non-dormant (growing) tropicals in winter. My husband, Bill, has set up tables with 75 watt light fixtures suspended on chains from our basement ceiling. These are not the more expensive ‘grow’ lights, but simple fluorescent tubing purchased at a hardware supply store, and I have mine placed on timers for convenience.

The advantage to this method is to store containers of cuttings (in four inch pots) and prized specimen plants of the more tender treasures that may have little or no natural dormancy, and, or, prefer to be kept growing. This includes cuttings of Acalypha (chenille plant), Agaphanthus, Alternanthera,  Begonia, Brugmanisa (angel’s trumpet), Coleus,

a picture of red and yellow coleus

Coleus is easily overwintered from cuttings.

Cordyline australis (cabbage palm), Cuphea, various palms, Plectranthus , Ruellia (Mexican petunia), succulents, Tradescantia (wandering Jew), and, or, specimens of Geranium, Breynia (Hawaiian snowbush), bromeliads, Croton, Clivia, Cordyline terminalis (Ti plant), various ferns, Hibiscus, and especially, elephant ears that don’t perform well with a sleep period, such as Colocasia esculenta ‘Black Magic’, and the more diminutive ‘ears’ including Alocasia x amazonica ‘Polly’, ‘Purpley’,‘Aurora’ or ‘Greenshield’.

In the fall, when nighttime temperatures are still in the 50-55 degree F range, after inspecting and spraying any plants for insect infestations, everything goes into the basement on wire tables held up on concrete blocks, placed 6 to 12 inches from the light tubes. Large specimens can be set on the floor near the lighting. This minimal lighting will suffice for the winter months when left on for 8 to 12 hours a day, providing just enough light to hold them over for spring, but not so much to induce active growth.

At this time it’s simply a matter of maintaining good sanitation (sweep up any fallen leaves), inspecting for insects, and watering sparingly.  I also use an oscillating fan for good air circulation, which minimizes potential problems, and a convenient washtub for watering is placed nearby, beneath my basement spigot. This done, I wait for the first light frost to ready the second group of plants I will bring in, large or mid-size specimens of woody tropicals.  These will be stored in their sleepy, or dormant, state.


Storing dormant woody tropicals….

Storing woody  tropicals in a dormant state is ideal if  you do not want to keep them growing as houseplants. They can be kept, most conveniently, in the containers they were grown in, placed in a dark or moderately well lit place, such as a basement, porch, or heated garage kept at 38 to 45 degrees (always above freezing). Those tropicals grown in the ground can be dug, cleaned and potted for easy wintertime storing. Either plastic or clay pots can be used. I use a bark-based soil-less mix like Fafard 51 or Metro Mix 700.

I never cut back my woody tropicals in autumn, preferring to wait until spring, when they are returned outdoors, unless the plants are too large to get in the door, or for the space I have provided for them.

a photo of mandevilla blossoms

Woody tropicals like Mandevilla can be left in their pots and allowed to go dormant in the winter.

This method works well for Abutilon (flowering maple), Allamanda, Bougainvilla, Brugmansia (angel’s trumpet), Brunfelsia ,Cestrum (night-blooming jasmine), Clerodendrum (glory bower), Duranta (pigeonberry), Fuchsia, Gardenia, Hibiscus, Galphimia (mexican gold bush), Gardenia, Justicia (shrimp plant), and Mandevilla among others.

After inspecting for insects, and spraying, if needed, begin to bring your containerized woody tropicals in for the winter months when temperatures dip into the mid to low 40’s or upper 30 degree range.   Many or all of their leaves will have fallen, leaving a bare, woody structure. It’s sleep time.

Wintertime care of dormant woody tropicals is minimal. Water sparingly, waiting until the upper 3 to 4 inches of the soil has dried before adding a small amount of water, perhaps enough to saturate the upper one quarter of the pot. Don’t soak the entire rootball, as I have found  this will only encourage rot.


Storing dormant bulbs and bananas…..

Plants that store food in underground tubers, corms and bulbs and die-back tropicals are among the easiest to overwinter indoors, and can be brought in last since their bulbous growth is protected from freeze beneath ground. These include canna, elephant ears, caladium, pineapple lily, gladioli, dahlias, tuberous begonias, crinum, bananas and gingers.  When leafy tops have died back, following a frost, start digging those plants you have grown in the ground.  Container grown specimens can be overwintered in the pots they were grown in. Make sure each plant is labeled as you dig them and set them aside. I prefer to wash the soil off of the roots to lessen the likelihood of bringing in soil born diseases and insects.  At this point, bulbs should be thoroughly dried out before being brought indoors, wrapped in newspaper, and stored in plastic bags for the winter.

True banana aficionados dig their plants and leave them intact– leaves, stems, and roots– storing them in an uncovered plastic wastebasket, or by simply wrapping the roots loosely in plastic, taking care to vent the plastic– by perforating it–thus allowing some air circulation. This is the best method to grow a mature banana, one you want to fruit, or reach grand proportions. Bananas store massive amounts of water, and in containers, are massively heavy to move, particularly Ensete ventricosum. I have chosen this simple method to store my container grown specimens– I chop off the stem (actually pseudostem) at pot level.  This lightens the load considerably, and the stem reemerges from the underground rhizome nicely in spring.

Now it’s time to place your bulbs, tubers and bananas in a cool, dark place such as a basement, garage or closet where the temperature remains above 35 degrees, let’s say 40 to 45 degrees.   Caladiums will prefer warmer temperatures, generally no less than 45 to 50 degrees. Winter care is minimal. Just remember to occasionally check for signs of rot, discarding any diseased bulbs or molded leaves. I never water my dormant, potted bulbs and bananas in winter.

Back Outside in Spring…….

It is my experience that dreams of tropicalismo and the itch to garden generally reach unbearable status by mid to late February. In my windowed basement, dormant and non-dormant tropicals easily detect the slightest lengthening of daylight and respond with new growth and swollen buds. I generally bring my plants back to the greenhouses by late February, and even those that stay in my basement until spring have fared well, despite their attempts to grow. If room is available where you can move them to brighter light and warmer temperatures, do so, and increase watering and fertilizing. Otherwise, don’t fret, just steady the course. Resist the temptation to water and coddle them, and dream of balmy May days, when night temperatures hover above 50 degrees, and they can be returned outdoors.

Chris Kelley is a self-taught gardener who, along with her husband Bill, owns Cottage Garden Nursery in Piasa, Illinois, where they grow and sell a wide variety of hardy and tender plants. She speaks and writes regularly on container gardening, tropical plants and other topics.