Hoya engleriana is a rare species, found in isolated locations in Vietnam, Laos, Cambodia, and Thailand in specialized habitat where it enjoys mountaintop mists.  Because of this unique habitat, it prefers some additional humidity for best growth, easily obtained with a humidity tray or an occasional mist with a spray bottle.  Their preferred temperatures are in the moderate range, and they like bright, indirect light, but never full sun.  The flowers of this particular species are especially desirable, and have a sweet, lilac-like scent that is particularly intoxicating in the evening around dusk.