Tropical means no frost or freeze - ever. Average above 55F. There are many different tropical climates. Some are low and very warm, some are higher elevation, with a cooler temperature regime. And a complication is the extreme high elevation equatoria montane climate. Here the temperatures are pretty much constant year round, where every day is warm and sunny and there is a frost almost every night. This is not ''tropical'', but a very unique extreme of the possible equatorial climates.
Some tropicals are ''Thermophiles'', where they resent temperatures below 60 F, (15 C) and will be damaged by temperatures below 50 F (10 C) Cacao, source of chocolate is usually sited as a thermophile. Shrubs from coastal low elevation areas can fall into this group. Some ficus species are sensitive to cool, some are not.
There are tropical alpine trees and shrubs like some of the high elevation Vireya rhododendrons from Borneo, which will not tolerate frost or freeze, but fail to thrive if temperatures rise above 78 F, or 25 C.
And there are a host of trees and shrubs that will do well ''between'' the extremes.
Clyde is right on target with his suggestions.
