What these people don't understand is that it takes thousands of years for plants to make those kind of adjustments. A single generation simply does not have the ability to make that kind of change. If you want a plant that is perfectly adapted to the climate where you are planting it, that plant must have originated from that place. In fact a good rule of thumb is to not bring in plants that have been grown from further away than a 100 mile radius.
Obviously that rules out the plants that I named earlier. Daffodils come from the Amaryllis Family and originated in Europe, North Africa and West Asia. Vinca also came from there. Those beautiful Camellia japonicas, as the name implies, came from Japan. Although there are native plum trees, the kind that produce commercial grade fruit are varieties generally hybridized from European and Japanese stock. Yes these plants will all grow and even at times thrive here, but they are not genetically adapted to be here.
I can thrive in all kinds of places, but when the weather turns cold, I need the help of a jacket and gloves. Polar bears live in the local zoo, but not without some help. These plants are not really any different. They will survive, but their flowers have opened too early and will most likely be lost. In extreme conditions, as has happened periodically in the past, the weather will simply be too cold or below freezing too late in the season or even too hot in the summer for these more sensitive plants from distant lands to survive.
There are some native plants that are also blooming. I have see trout lilies blooming in the wet land areas just above the creeks and temporal ponds and red maple blooming in the forests. These will still be blooming and pretty after this little winter reminder. Some of the colonies of trout lilies that I look for each year are likely to be several hundred years old. That's a long time to be living in a single spot - generation after generation. Red maples have most likely been here growing in a similar form to what we see today here in North Carolina since the last Ice Age. It stands to reason that these plants are better equipped to handle the changes in weather that Mother Nature throws their way here. They have had generations to adapt. Those that could not adapt have most likely died out long ago leaving only the hardy ones behind.
There is a place and a very real human demand for ornamental plants. Those plants are often not native or even grown locally. When planting them, remember that weather is unpredictable and that they will show effects of those changes. If the results of broken and drooping or brown flowers are a problem for you, than my advise is to switch to natives. They will be better equipped to handle the local conditions.