I agree that it is a Gesneriad, specifically, some species/variety of Aeschynanthus, aka Lipstick Plant.

After looking up some pictures of penstemon husker red I think that you are right. Thanks so much!

Wow, you people have such an experience with it. I love that plant and while it does spread around a bit it is nowhere close to being the pest you describe! This year was first year I actually dug out few pieces to give away after having it for 3 years. It is not hard to remove where I do not want them either. I also have variegated lyshimachia Alexander which also behaves. Again my garden is informal so I really do not care if they do not form clump or migrate a little, have not noticed them migrating more than couple of feet from original placement. Maybe it is because I grow them in the shade but have not had any problems from them. I have bed of lysimachias, tiger and asiatic lilies,aconitums, macleya cordata, corydalis lutea which reseeds like crazy but very happy and blooms all summer and dwarf yellow and variegated bamboo. Those ones do try to get into walking path grass but not invasive enough due to being not fully cold hardy here. Out of all of the only bamboo is kind of hard to dig up.

RE: original topic... 3-5 cups per day is a bit too much water. Otherwise, that's simply the plant's behavior. The leaves get like that due to sun exposure. As long as they aren't wilted or drooping or turning white or black, they're fine. As for the blooms, they can turn brown or limp around the edges of the petals, especially if in direct sunlight. Also, hydrangea blooms tend to turn brown as they age. I theorize you got this as a gift or otherwise from a florist source. It will behave like this when subjected to natural conditions 100% of the time, especially when raised in unnatural conditions (a.k.a. Greenhouses). Growth and blooms that occur in natural conditions will be more apt to handle them. Also, fair warning, if you plant a "topiary" hydrangea "tree", it will come back as a regular hydrangea with a dead stick in the middle next spring. This forum really needs sticky threads on Florist Hydrangeas and winter hardiness. Who's with me?!