How to keep tropical plants alive, even thriving, during a Minnesota winter

More than 40 years ago, my parents went to Hawaii and returned with what looked like three coffee beans, each sporting a little orange mustache.

They were bird of paradise seeds, brought back to Minnesota for this fledgling teenage gardener. Clueless, I stuck them in some soil and waited months before a tiny green spear popped out of the little pot.

In the decades since, that now 5-foot-tall plant has been dragged from the Twin Cities to rural Minnesota, North Dakota, back to the Twin Cities and to Connecticut before it returned to Minneapolis to stay. It's proof that ignorance is no barrier to growing tropical plants in cold climates year-round.

That said, having a plant survive and having it thrive are different things. My bird of paradise never flowered until I began setting it outside in a protected sunny spot during the summer. Now, I get four or five exotic blooms on the plant between February and May each year.

Wintering over tropical plants indoors means offering just enough care — or sometimes neglect — to nurse them through the chilly months so they can burst into full glory again the next summer.

Tropical hibiscus, jasmine, bougainvillea and small citrus trees will do quite well indoors if they're in a bright spot where temperatures are at least 60 degrees. All of these plants need a gradual transition to the reduced light of the indoors. Water sparingly and don't fertilize — the plants want to rest during the short days of winter.

Make sure you've checked the plants for pests before moving them indoors. It's a good idea to isolate outdoor plants in a basement or other secluded spot for a few days, washing both sides of the leaves with a weak solution of dish soap in warm water before moving them to their winter home.

One thing to remember is that if you intend to winter over a tropical plant, make sure it stays in a pot that's small enough to easily move inside. When it's growing outside, you can bury the entire pot in the ground or in a larger pot as part of a group planting.

I was reminded of this lesson last year when I bought a beautiful banana plant with purple stippling on its leaves, unpotted it and added it as an accent in a big outdoor pot. The plant tripled in size over the summer and, as I feared, by the fall it was impossible to remove the plant from the pot intact.

Had I kept the banana in its own pot, I could have overwintered it in a cold, dark basement room where it would have gone dormant, and I could have repotted it in the spring for another summer of growth.

This page at Gardener's Supply Co. answers many questions about overwintering tropical plants:

gardeners.com/how-to/how-to-overwinter-tender-plants/5019.html

I also have a lemon tree that flowers in the spring but pouts for much of the summer. I don't have a good spot in the house that's both sunny and warm in the winter, and if it doesn't bear fruit soon, I'll give that away, too.

As for the bird of paradise I received so many years ago, the plant means too much to me to be dumped; during winter it is perfectly happy growing under a shop light for a few months in my chilly basement.

To prevent it from growing too big and heavy for me to lug up and down the basement stairs each spring and fall, I divide its fat root ball with an ax every few years. The divisions go to friends and acquaintances.

A couple of years ago, two of the divisions headed south to Florida, where another Master Gardener gave the plants to her daughter. I smile thinking that those little seeds I planted decades ago in a pot on my bedroom window sill in Bloomington have spawned descendants that are scattered around the country.

I won't be giving up that plant anytime soon.