Work Rant.
Ahhhh.....yes, the corporate "people are our most important asset" world. You'd be surprised how far just clamming up and doing your job will take you. Even though they say they want your input and ideas, sometimes it comes across as you looking like you want to: A) be the brainiac new kid B) steal some thunder from your boss and maybe have some upper level management ask him "why didn't you think of this?" C) Just finding a way to do less work.
I think you have to "read" a situation and try to be that model employee in their mind. BTW, if you go up and ask your supervisor every 15 minutes or so "I'm done with that, do you have anything else for me to do?" it might go a little better. Let him know in his mind that you're on HIS side. And lastly.....when he asked you to go water the trees (he might have even KNOWN they were already watered!) that might have been------> just go look busy until we have something for you to do. Don't expect praise or thanks or big respect for your ideas......not yet. You're a newby temp.