Plants can inhabit nearly every climate on Earth. They live in hot and dry deserts, cold arctic regions, rainforests and just about everywhere in between. Plants seem to have it all figured out. Some even know how to live in our homes as houseplants, although they probably did not plan it that way. Most houseplants are tropical plants that are naturally endemic to tropical ecosystems.
It is actually their tropical heritage that makes them more comfortable in our homes. Tropical climates tend to be conducive to proliferation of all kinds of plants. Those that want to live there must be competitive. Trees compete by growing faster and taller than other trees. Vines compete by climbing the trees. Understory plants that live under taller plants compete by needing less sunlight.
It is these understory plants that do not mind the shade of our homes. Even those that like bright ambient light might never expect to get direct sun exposure. The various ficus trees that might naturally grow tall enough to reach the top of a forest canopy in the wild are still understory plants while young. Because they know how to use resources efficiently, tropical plants do well in pots.
However, these advantages are not so useful out in the garden. Tolerance to partial shade also means that some tropical understory plants need to be sheltered. If too exposed, foliage can get roasted by sunlight or arid wind. (Most tropical climates are more humid than local climates are.) Complaisant roots do not disperse well enough to sustain lush foliage without regular watering.
Ironically, roots of the various ficus trees are very aggressive because they to not disperse deeply, but instead spread out at the surface of the soil where they grow into exposed root buttresses.
The most familiar weakness of tropical plants is their susceptibility to frost. Even though it does not get very cold here, it gets cool enough in winter to offend plants that would never experience cool weather in the wild. Actual frost can severely damage foliage, and can even kill some tropical plants.
Tony Tomeo 
I can keep tropicals in pots outside all summer, but they are moved to the garage for winter. I find that most don’t even like temperatures in the 40’s.
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Even without frost, some of the tropical plants just don’t know what to do in weather that is cooler than what they are familiar with.
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My Poinsettia is currently enjoying life on a window ledge and seems quite happy. I have repotted it into a slightly larger pot and cut it back a bit. I am hoping it thrives so that when I bring it in this fall it will survive the winter. I may do the 12 hours a day in the closet thing to see if I can make it bloom, but we’ll see. I feel bad for it. I think it probably wants to be a tree in Houston.
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In Honolulu, there is a patch of poinsettias along one of the highways (or there used to be). For most of the year, the plants are simply allowed to grow — they get plenty of water, and are warm all year. In September or thereabouts, they are covered until late-November to prevent the bracts from turning red too soon — then in early December they are uncovered and they all turn red quite quickly!
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That’s fascinating–and I bet it was fun to watch. Someone was looking out for their coloration!
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It sounds like they were grown as a horticultural commodity rather than in a landscape.
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They are not an easy crop to grow. I remember all that went into scheduling them when we were in school. It is probably easier where they are grown in Hawaii because they do not need to do it in greenhouses where pathogens proliferate.
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I never had the patience to get them to bloom in time for Christmas. I just let them grow as houseplants, although they are not one of the best. One grew outside for many years, but was killed by a bad frost years ago.
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An interesting take on houseplants from the plant’s perspective. My sweetheart put my regal pelargonium outside for a summer holiday, insisting that it ought to have a day in the sun. It came back with its white flowers covered in greenflies, which makes me think it would be a good decoy plant.
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If greenfly is aphid, they should not be overly voracious on pelargonium. I really do not know though. I have never grown one as a houseplant. They stay outside where aphid are mostly controlled by predatory insects. Ants do not cultivate aphid on pelargonium.
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It is aphid. It’s a regal and flowers steadily, so I just cut the flowers off and got rid of them that way.
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