I do know of a perennial flower that is tough as nails, beautiful when it blooms, fragrant, tolerant to humidity, heat and frost. The only thing is that it blooms from spring to summer, but not through fall. It's called the Lady Banks Rose. It's a climbing rose with little yellow flowers that will completely cover the plant when it blooms. (Some cultivars have white flowers, but it has been my experience that the yellow flowered Lady Banks Roses are more fragrant.) They are practically thornless (or prickleless to be more scientifically correct). They are resistant to insect infestation and disease infection. I really love this rose. The only thing is, you would have to either have a large area to let it mound as it grows, or have a trellis or arbor to let it climb up. They can get rather large if you don't prune them. This is fine though. I think they are quite beautiful when they mound. You would probably need 20 feet of space to let it grow in that manner though. I hope this is helpful. Let me know if you have any further questions. Cheers...Dr. Robby