It depends on the winter, the climate here is not nearly as consistent and tropical as yours. We have hot dry summers with temperatures hitting 100 quite often during August, but even on those hot days nighttime lows will fall into the 60's. Winters are cold(ish) and wet with occasional frosts but seldom anything much colder than that; but overnight lows in January and February will often be freezing or slightly below. This winter was very wet and warmer than normal and I did see some valerian that was still alive - barely. Generally it does die back. We get something around 1/3 the annual rainfall that you do and the vast majority of that falls from November - March. By the time we are in the warmer months late May through September it is uncommon for us to have any significant rainfall. For example, In the last roughly month we have received .06 inches of rain...almost not measurable...and the valerian in the alleyway at the end of the lane is thriving and in bloom. Again, it looks scraggly as hell compared to yours, but that is how it grows and I think why it flowers; it wants to set seed before it pops its clogs.
