The definition of a houseplant is generally this: a plant that has adapted to indoor conditions or that has adapted to living in a container or a pot.
It was on a road trip from Delaware to Florida in the 1990s that my definition of a houseplant began to change, especially once we entered Florida and noticed decorative crotons (Codiaeum variegatum) growing directly in the ground as accent plants. Up until then, I had always thought a croton was a glossy, paint-dappled-looking houseplant—the kind that only grows in pots sold at Kmart.
Such compartmental thinking regarding houseplants versus outdoor plants changed after that Florida trip. Maybe the line between houseplants and outdoor plants is not as hard and fast as I had thought.
I guess you could say that my understanding was limited to my particular gardening zone with its freeze and frost dates that dictate the best months for plant survival outside. I had never entertained the idea of bringing my houseplants outside, even in good weather. Yet according to the data in the dates, my frost-free growing season is approximately 199 days. That's about six months, plenty of time for experimentation.
Furthermore, with six to seven months frost-free, why not try something new?
Since then, I regularly take a few types of houseplants outdoors each spring to live over the next two seasons and bring them inside when frost is imminent in the fall. Shown here is a potted Tradescantia zebrina (Wandering Jew) thriving under a Mimosa tree. This houseplant (in certain zones) absolutely adores fresh air and dappled sunshine in the shade of the tree here in zone 7a.
It amuses me on my daily trek around the yard to see this specimen that I once thought of as just a "houseplant" sending out runners that root all over the base of the tree and the trunk.
This particular houseplant will stay put over the winter, getting a cover of leaves and straw for good measure. Its long stolons will get clipped for propagating winter houseplants indoors. In the spring, the Tradescantia may pop up again, but not if the winter before was especially harsh. Hence the stolon clipping—so that I do not lose the specimen altogether.
Another attractive plant, Tradescantia pallida (Purple Heart), is a bit more rigorous. It is an indoor houseplant during the cold months up here in Delaware. In the springtime, it is readily available as a bedding plant or as an accent for potted plants outdoors.
My Purple Heart grows nicely outdoors all year except for winter when it gets the same treatment as its cousin, the Wandering Jew. Loathe to lose this striking purple specimen, I clip several healthy stalks in mid-to-late fall for bringing indoors. The outdoor rooted part gets covered well with leaves and pine needles. It pops up faithfully after winter is over.
Living outdoors, these plants look a little rough but seem to be happy. After bringing cuttings in for the winter, the new plants grow a little leggy and lose their brilliance, but that is to be expected in an indoor environment. The tradeoff is that they get more attention and far fewer insect pests indoors.
The reverse idea is to grow outdoor plants indoors. Why not?
Each autumn, there always seems to be a vigorous young Zinnia elegans that is thriving in the garden right at frost time. It obviously sprouts from a seed dropped by a mature, flowering zinnia—but too soon, and badly-timed: The young seedling should be this size next spring. Not now. Not at frost.
Naturally, out of pity, I bring the zinnia indoors. It is a tradition now to have a flowering zinnia in the house alongside my other houseplants on the winter windowsill.
The pumpkins started out in a dab of soil and begged for more, so I obliged by potting them up. And up.
Their flowers were amazing and beautiful to behold in the dead of winter. This was indeed a novelty, and I shared pumpkin bloom photos on Facebook.
The pumpkin plants lasted a long time, leading me to wonder what I would do next because I knew that they would create vines in ever-increasing lengths. Would they last until spring? And what about pollination? I was not about to bring bees into the house. (Hand-pollination is a fascinating subject of which I had yet to discover.)
After reading about hand-pollinating pumpkin blossoms, I was intrigued but soon realized it was time to find a stopping place. Time did not permit such devotion to my indoor pumpkin novelty plants. The pumpkins were fun, I proved that I could grow them indoors in the wintertime, and then the novelty began to wear off.
The story ends on a sad note when to my dismay, many fine webs seemed to appear overnight, covering my indoor pumpkin plants—with red spider mites. As soon as I realized the gravity of the situation, I had to take the plants outdoors to allow them to perish in the quiet wintertime garden.
If this had been a greenhouse business situation, the outcome would have been very different. But it was just a fun thing to try inside of a small ranch home.
The pumpkin plants had a proper burial and will always live on in my memory, especially in the photographs I keep of my gardening adventures.
From now on, I will grow crops outdoors, and houseplants, for the most part, will stay inside during freezing weather.
—At least until my next experiment.
More about red spider mites on indoor plants from Magic Cactus
More about growing pumpkins by megagrow.com