Thanks for sharing the pictures. I don't know whether this post is slightly off-topic, but it may be a thought worth sharing which immediately came to my mind.
These flower-based decorations remind me of a local tourist attraction in one of the towns of my homeland (located at a distance of about 250 from where I live now).
A huge public clock, located somewhere the an inner city area of TimiÈ™oara.
Flowers/flower arrangements/flower beds are the main "building material" of this clock (while the mechanical part is, certainly, consisting of more conventional materials, the flowers are still the most visible, especially in warmer seasons). Unlike the thread-starting pictures, it's not linked to any custom, tradition and special occasions, it's only limited to a single location alone and little more than a very elaborate urban amenity, but is pleasant to look at just the same.
I've only seen it a few times, while passing by in a car, yet was impressed even without having the time to stop and admire extensively.