Life is very varied, and if anything teaches us about life on Earth it is that anything is possible, but this is different to being probable.
My question would be: How would such plants evolve? What did they evolve from?
Presumably the events that have occurred on the Blue Moon is the same events of that of Earth - a spark of single celled life, invention of photosynthesis (and thus plants), a great Oxygenation event and perhaps sexual reproduction to push evolution to its current state through sexual selection, and a symbiotic balance of perhaps animals and other carbon dioxide producing mechanisms to create an environment of stability in which advanced species like this could evolve.
Considering it is a plant, presumably it is using photosynthesis to grow. This would normally then be green, not blue, and indeed blue light is not an efficient light for photosynthesis to be an efficient method of converting carbon dioxide to carbon.
It is true that capillary action from the ground limits the height of trees, access to water top down would reduce this impediment. A kilometre is a long way though, one would expect stability to be a major issue (especially for the first) - I would not expect this likely unless gravity and wind is a lot less.
Also, not sure of the utility of the elevated lily ponds evolutionarily, besides that of obstructing your neighbours access to light to give you the best advantage possible. However if this was the case, others would grow taller to compete with you, I would expect the plants therefore to be jostling and quite varied in heights, eventually reaching an uneven, but dynamic, loose equilibrium (much like the Congo in Africa).
Evolutionarily, there would be a varied and divergent series of other species either along the way or in parallel, these would also compete for light too. Like the Congo, it would result in a morass of different colliding species, for which this would be only one.