Probably the first tropical perennial I ever tried to grow outside in the summer was a bougainvillea vine. I special ordered it because it had a white flower tinged on the edges with red. Of course, when it arrived it was spindly as most mail order plants tend to be but it immediately took hold and started to thrive. I immediately potted it up in a nice container. I was thrilled that I actually got a few bracts of its delicate blossoms by mid-summer. At the end of September, I brought the woody vine indoors for the winter since it was a zone 10 (9 with protection.) Within a month, it had dropped every single leaf. Days later I started to see the beginnings of spider mites on it. I tossed it for fear it might infect my houseplants. I tried again a year or two later with a beautiful Mandeville I had gotten from Home Depot. It did the same thing. Fallen leaves all over the place. At first, I suspected I was over watering it. But, then, I did a little research and found that there’s a reason these tropical aren’t typically promoted as being good houseplants. They simply hate our dry, heated indoor conditions during the winter. It’s too unnatural for them. Then, and I can’t remember where I found it, I came across an article about simply making tropicals go dormant in the winter.
Most of our houseplants are houseplants for a reason. They’re typically from milder climates but have proven to be able to survive and often thrive in our indoor conditions, year-round. Every year by Memorial Day, all of my houseplants go outside. I arrange them amongst other seasonal container gardens and they usually love it. Some tropical and even sub-tropical plants just don’t adapt to our indoor winter climates despite us keeping the thermostat set at 68 degrees or warmer. It’s our dry, artificially created atmosphere they can’t tolerate. A great solution to saving these plants we’ve invested money and time in is to simply over-winter them somewhere cold and dark and yet not below freezing temperatures. Think about where in your home you could stash these summer beauties for the winter where they won’t experience prolonged temperatures below freezing. If your garage is attached to your house, there’s a good chance that’s a likely place. Got a bulkhead basement entry? Right under those stairs is a good spot if you mostly leave the bulkhead closed throughout the winter. Your basement itself is a prime spot though you’ll want to find the coolest spot you can. You want to force the plant into dormancy. It will lose its leaves and basically go to sleep until spring. A couple of times during the winter, sparingly water the plant just to keep it from desiccating. It should be mostly dry, though.
Around mid-March, you’ll want to drag those slumbering tropicals out and increase watering just a tad and place them where they’ll get just a bit warmer… not too warm but just enough to wake them up and you’ll soon see little green nubs of new leaf growth begin. If you can, get them near a natural source of light. That would be beneficial, too. If you can’t give them a transitional spot in your home between late winter/early spring, don’t worry about it. Once it’s warm enough that there is no danger of frost (typically mid-May or before Memorial Day here in southern NH,) bring your exotic beauties out to a semi-shaded spot outdoors and start watering and feeding them. The shade lets them start developing gently before exposing them to the full sun they’ll eventually crave.
Both Bougainvillea and Mandeville are good candidates for over-wintering this way. Other’s I’ve had good luck with are Agapanthus (Lily of the Nile) and Brugmansia (Angel’s Trumpet.) The very first gardening article I wrote for ELF seven years ago was about my love for Agapanthus. As a container plant, they’ll rival any lush fern you might consider with their strappy foliage and balls of bloom on stalks that burst forth two feet above the foliage. There’s white and blue varieties available and they’ve become more popular in recent years and can be found in lots of nurseries and garden centers. Same with Brugmansia. It’s a gorgeous tropical with huge trumpet-shaped blossoms that can easily be trained into tree form. Particularly the white blooming variety releases an unearthly beautiful scent at dusk and makes a great container plant adjacent to your moon garden.
During the Victorian era, cultivating tropicals in non-temperate climates was a passion of the wealthy primarily. You don’t have to be wealthy, though, to enjoy the exotic beauty of tropical plants in your home landscape today, though. You can just enjoy their languid beauty during the summer and then tuck them to bed during the winter.