In France it is a municipal responsibility and in small towns and villages, the Mairie will speak to a local artisan who will be paid to work on them a few hours a week.
What is the really clever thing in France and I wish British authorities would look and learn, is that these floral planting, often evergreens and shrubs are used as part of traffic calming schemes, The main road through a town, will have a narrow concrete island down the centre of the road, planted up with ornamental everygreens, There will be chicanes at regular intervals down a street, full of plants, roundabouts are planted up., with planting (and rocks) in the corners to stop lorries running up on them and threatening pedestrians.
I know of two long (several miles) downhill roads in to major towns (Granville & Cherbourg), where a wide straight urban major road, has been calmed down and beautified at the same time by such plantings (and in each case the lorries now use the bypass, so they have been discouraged as well)