I've found that some Hoyas just naturally have the upwards and outwards growing habit while others naturally want to hang down. If they hang down and you want them to have the upward growing appearance, they have to be tied to a trellis or some other support. We have a member in Hawaii wo had a variety of Hoya that naturally grew up the sides of a tree and once the vines reached the top, they turned and grew back down towards the ground.
