Ok, when I GM PFS scenarios, I feel part of my job is to communicate the story to the PCs. Often times it requires me to come up with creative solutions to give story elements to them (things that usually do not impact the primary or secondary success). Examples being lowering DCs or giving multiple chances via different skills. My style has me playing with the players not against them like I see so often.
That being said. I did not enjoy running this scenario, nor did the players have much fun playing it. They completed it with 100% success as far as the chronicle goes, but walked away knowing nothing about the Verdant Spark or why anything was happening.
The party had no one that could use the scroll of speak with plants..
If I had to make a change, maybe there is a 1st level Bard/druid/ranger in town if no PC can use it?